Dissertations / Theses on the topic 'Urban hydrology'

In many parts of the world snow melt runoff influence discharge from combined sewer overflows (CSO) and flooding in urban drainage systems. Despite this, urban snow hydrology is a field that has received little attention from the urban drainage community. The objectives of this research were to better understand urban snow hydrology and through field work and hydrological modelling quantify effects of anthropogenic activities (AA) on snow distribution, and melt in an urban environment. This means in principle how the presence (design geometry) and operation of roads and buildings influence the snow distribution and melt in urban areas. The Risvollan urban catchment (20 ha) located in Trondheim, Norway, was used as a study area. A literature review of urban snow hydrology was also carried out.

A gridded urban hydrology model (GUHM) was developed as part of the study. The principal idea of the GUHM is to subdivide an urban catchment into orthogonal equal area grid cells. The snow routine in the GUHM is based on an energy balance approach, which together with a soil-runoff routine is used to calculate a time series of rain, snow water equivalent (SWE), snow melt, and runoff, for each grid cell. In GUHM, processes such as snow clearing of roads, locally low albedos, heat/shadowing from buildings, and effects of slope and aspect are included in the model structure.

A technique for observing time series of snow covered area (SCA) for an urban catchment is presented. The method is based on image processing and neural network technology to calculate SCA from a time series of images taken from a tall building in the Risvollan catchment. It was shown that SCA on roads and roofs in general becomes more rapidly snow free during melt periods compared to the park areas of the Risvollan catchment. This can be explained by snow clearing of roads, snowdrift from roofs and high snow melt rates on roofs and roads. The high melt rates was attributed to locally low albedos in vicinity to roads, rooftop snow packs exposure to wind and solar radiation, in addition to anthropogenic heat release from the roofs themselves.

Field observations of SWE were carried out in the Risvollan catchment and it was shown that areal mean SWE located on/or nearby roads and buildings were significantly lower during mid and end of the winter, than in park areas. This can be attributed to higher melt rates caused by AA. A time series of SCA and SWE was obtained through field work for the period from 2000 to 2003 in the Risvollan catchment.

The GUHM was applied and calibrated for the Risvollan catchment for a three year period. Two seasons were used as validation period. Comparison between the simulated and observed SWE, SCA and runoff data showed that the GUHM was able to simulate snow accumulation and melt for whole seasons with short time resolution (1 hour) satisfactory.

The GUHM was used to quantify effects of AA on snow distribution and melt for six different land use scenarios in the Risvollan catchment for the period June 1998 to June 2003. The modelling results showed that when the area coverage of buildings and roads increased, the SCA and SWE more rapidly decreased during melt periods. Because of this more runoff will be produced in the early winter season (Jan-March) compared to if the catchment had been covered with only sparsely vegetated areas.

The simulation results showed that when the impervious surface covers of a catchment increase, the peak and volume runoff will also increase, as expected.

Both the field observations and the hydrological model study carried out in this work showed that AA lowers SCA and SWE more rapidly in an urban environment compared to more untouched terrain. The reasons for this are redistribution of snow, and strong snow melt rates on roads, roofs, and in snow deposit areas. Low albedos and anthropogenic heat release are the main reasons for the enhanced snow melt rates.

Urbanization is continuously growing all over the world. Both developing and developed countries encourage rapid expansion for increased growth and production. However, urbanization in combination with climate change can lead to higher chances of extreme flood events. Mankind always settled around rivers and floodplains that are naturally more flood prone areas, making stormwater modeling and urban planning indispensable for safety and reduction of flood risk.Until now many important studies have been conducted on the dangers of living in floodplains of urbanized cities, but most of them are about developing countries such as Bangladesh or Vietnam, leaving a noticeable gap in the developed world. However, all these researches share one thing in common as they do not take into account the interactions between water and society by ignoring the constantly changing human factor.Socio-hydrology is a new branch of hydrology closely related to Integrated Water Resource Management (IWRM) that tries to explore this dynamic relationship. This study explores the historical evolution of a highly urbanized industrial city in Finland and attempts to understand both the human and engineering effects of urbanization. The city of Pori is the most flood prone area in Finland, which makes for an important study that will yield important results and possible recommendations for future research, while for the first time incorporating socio-hydrology, the human factor and flood risk in a major European city.This is an empirical project with data collected from various different sources put all together for the first time that could change the perceptions of both inhabitants and scientists and be the basis for a more thorough, modeling based research in the future. The research question of this dissertation is how socio-hydrological dynamics have affected flood risk changes over the past decades in the city of Pori.
Urbaniseringen växer fortlöpande över hela världen. Både industriländer och utvecklingsländer befrämjar snabb expansion för ökad tillväxt och produktion. Dock leder urbanisering i kombination med klimatförändring till högre risk för extrema översvämningar. Människor har i alla tider bosatt sig runt vattendrag och flodslätter som naturligt är mer benägna att översvämmas, något som gör att dagvattenhantering och stadsplanering är absolut nödvändigt för ökad säkerhet och reducerad översvämningsrisk.Fram tills nu har många viktiga studier genomförts som behandlar farorna för människor bosatta i urbaniserade städer intill flodslätter, men de flesta av dem har utgått från utvecklingsländer som Bangladesh eller Vietnam, något som lett till en märkbar avsaknad av information gällande industri-länder. Gemensamt för dessa studier är dock att de ignorerar den ständigt föränderliga mänskliga faktorn och på så sätt inte tar i beaktning interaktioner mellan vatten och samhälle.Socio-hydrologi är en ny gren inom hydrologi som är nära besläktad med Integrerad Vattenresurs-förvaltning och som försöker utforska detta dynamiska samspel. Denna studie undersöker den historiska utvecklingen av en starkt urbaniserad industristad i Finland och försöker tolka de mänskliga och tekniska effekterna av urbanisering. Staden Pori (Björneborg på svenska) är den mest översvämningsbenägna platsen i Finland, vilket gör denna studie till ett viktigt arbete för att ta fram betydelsefulla resultat och eventuella rekommendationer för framtida forskning. Dessutom inkorporeras socio-hydrologi, den mänskliga faktorn och översvämningsrisk för första gången i forskning gällande en större europeisk stad.Detta är ett empiriskt projekt med data insamlat från olika källor som sammanställts för första gången och som kan förändra både invånares och forskares synsätt, samt vara en grund för mer utförlig och modellbaserad forskning i framtiden. Frågan som denna avhandling försöker besvara är hur socio-hydrologisk dynamik har påverkat förändringar av översvämningsrisker i staden Pori i Finland över de senaste årtiondena.

The management of urban runoff has evolved along with the advancement of understanding of runoff environmental impacts. Besides the impacts on water quality in the receiving waters, the impacts on the urban hydrologic regime include reduced infiltration by the sealing of pervious land, reduced evapotranspiration by removal of vegetation, and the resulting increase of stormwater runoff peaks and volumes causing flooding, and ultimately degradation of receiving waters. In such considerations, urban stormwater management benefits from the implementation of Green Infrastructure which includes decentralized vegetative controls that capture and infiltrates rain where it falls and thus reduces and improves stormwater runoff. An example of small scale elements of Green Infrastructure are traditional grass swales. Through shallow depressions with mild side slopes grass swales collect and infiltrate stormwater from parking lots and roads, while runoff flows are attenuated and further conveyed depending on the hydraulic loading. Grass swales usually operate reliably and their maintenance needs are well understood. Their hydrological performance is, beside their dimensions and the contributing area, determined mainly by hydraulic and soil-related hydrological parameters that change with the intensity of the storm. Yet, because swales discharge to downstream drainage elements, either to the conventional sewer system or to other stormwater management facilities, the knowledge of the underlying inter-related processes and influential factors that govern the hydraulic and hydrological performance of grass swales is required. Against this background, this thesis is devoted to such questions as (i) what are the differences in the hydraulic and hydrological performance of the studied swales, (ii) how do soil characteristics, including the antecedent soil moisture, influence the swale water balance for various hydraulic loadings; and (iii) how can the related hydrological processes be simulated in high-resolution and reliably predicted using a grid-based, distributed model. For this purpose, full-scale studies were performed in three 30-m grass swale sections in Luleå, Northern Sweden, by collecting hydraulic and hydrological data based on routine storm events mimicking block-rainfall storm events of 2 months and 3 years recurrence. The resulting runoff and soil moisture data were used to calculate the swale water balance, to derive event hydrographs and to obtain calibration and validation data for model simulations. The experimental results showed that the relative swale flow volume reduction decreased with an increasing soil moisture and indicated the transition in dominating swale functions: at low initial SWC, runoff was highly attenuated (up to 74%), but for high SWC, the conveyance function dominated (with attenuation as low as 17%). Runoff flow peaks were reduced, proportionally to the volume reductions. Swale outflow hydrograph lag times varied between 5 to 15 minutes and decreased with increasing soil moisture. The swale wetness affected runoff formation, attenuation and subsequent outlet discharge and, for the short-duration events tested, only the top soil layer contributed to these findings. In the three swales tested, soils, initial soil water content, saturated hydraulic conductivity and topography varied spatially significantly. Double-ring infiltrometer measurements resulted in values of 1.78, 4.04 and 9.41 cm/hr (n=9) in the three swales tested and deviated from estimates from averages of spatially integrated infiltration rates. However, with regard to spatial variability, only the topography, described as irregularities in the swale bottom slopes affected the swale runoff dissipation and conveyance in the early phase of the events. Together with estimates of the water stored in the top soil layer, 4-32% of runoff volumes from the mimicked 2-month storm were temporarily stored. The distributed model Mike SHE was found capable of simulating swale drainage processes, when properly calibrated. Close agreement (NSE>0.8) was found not only for the measured and simulated swale outlet hydrographs, but also for the changes of the soil moisture in the top soil layer, which shows rapid increase up to the saturated soil water content, but minor or no progression in depths of 0.2 m. The model output was little sensitive to the initial soil water content, especially for low inflow which resulted in larger residuals in simulated runoff peak flows and volumes. As in field measurements, spatial variability of the initial soil water content had no effect on the swale outflow, but the accuracy of the topographical representation. The thesis findings include several implications regarding effects of the assessed parameters in the application of the model for swale flow simulation and eventually the design of grass swales.
Urban dagvattenhantering har utvecklats parallellt med en ökad förståelse för dagvattnets allmänna miljöpåver­kan. Utöver ytvattenkvalitén i recipientvatten påverkas även den hydrologiska regimen genom reducerad infilt­rationsförmåga i mark orsakad av allt tätare ytskikt samt reducerad evapotranspiration orsakad av minskad vegetationsutbredning. Detta ger både förhöjda toppflöden och avrinningsvolymer, vilket kan resultera i över­svämning och slutligen en försämrad ytvattenkvalité i recipienterna. Dagens urbana dagvattensystem förändras mot en högre grad av grön infrastruktur som en central systemkomponent. Decentraliserad omhändertagning av dagvatten såsom svackdiken utjämnar och för bort dagvattensflöden, samtidigt som de fungerar tillförlitligt och deras underhållsåtgärder är välkända. Uppbyggda med små svackor och låglutande slänter samlar svackdiken in och infiltrerar dagvatten från parkeringsytor och vägar. Dessa svackdikens hydrologiska funktion bestäms av en rad faktorer, utöver teknisk dimensionering och avrinningsområdets storlek och hydrologi, även av hydraulik och jordartsrelaterad hydrologi som förändras beroende på respektive nederbördstillfälles intensitet och varak­tighet. Eftersom svackdikens utflöde passerar nedströms liggande dagvattentekniker/anordningar, antingen konventionella ledningssystem eller andra teknologier, krävs full förståelse och kunskap om de faktorer som styr svackdikens hydraulik och hydrologi. Mot denna bakgrund fokuserar avhandlingen på frågorna (i) vilka skillnader finns med avseende på hydraulisk och hydrologisk prestanda för de studerade svackdiken, (ii) i vilken mån påverkar markartsförhållanden, inklu­sive ingående markfuktighet, svackdikens vattenbalans vid varierande hydraulisk belastning; samt (iii) hur och i vilken mån kan ovanstående simuleras högupplöst och förutsägbart, via den rutnätsbaserade distribuerade mo­dellen Mike SHE. Därför har fullskaliga studier bedrivits i två 30 m långa svackdiken i Luleå kommuns södra stadsområde, där hydrauliska och hydrologiska data insamlats baserat på standardiserade nederbördsförlopp, återskapande blockregn med 2 månaders och 3 års återkomsttid. Data för avrinning och markfukthalter använ­des för att beräkna svackdikenas vattenbalans, nederbördförloppens hydrografer samt erhålla kalibrering- och valideringsdata för modellsimuleringar. Resultaten från experimenten visade att den volymetriska flödesre­duktionen minskade relativt sett med ökande markfukthalt, indikerande en övergång för svackdikets domine­rande funktionalitet: vid låga initiala SWC var avrinningen tydligt dämpad (upp till 74%), medan för höga SWC innebar att transportfunktionen dominerade (med dämpningsgrad ner mot 17%). Avrinnande momentana topp­flöden reducerades proportionellt mot volymreduktionen. Laggtiden för svackdikets utflödeshydrograf varierade mellan 5 och 15 minuter och reducerades med ökande markfukthalt. Fuktförhållandena i svackdiket påverkade avrinningsförloppet, flödesdämpning och efterföljande utsläpp, och enbart svackdikets översta markskikt berör­des under de kortvariga bevattningscyklerna. I de tre testade svackdikena varierade jordart, initial markfukthalt, mättad hydraulisk konduktivitet och topografi signifikant. Mätningar med dubbelrings infiltrometrar gav föl­jande resultat, 1.78, 4.04 samt 9.41 cm/h (n=9), vilket avvek från medelvärdesbaserat estimat från spatialt inte­grerade infiltrationshastigheter. Med avseende på spatial variabilitet påverkade endast svackdikenas topografi, i form av ojämnheter i och nära dikesbotten, avrinningsförloppen och bortledning under den inledande fasen av regnhändelsen. Sammantaget med uppskattningar av den lagrat vatten i marklagrets toppskikt, bedöms 4-32% av svackdikets ytavrinning från ett simulerade nederbördtillfälle med 2 månaders återkomststid kunna lagras tillfälligt. Mike SHE befanns kapabel att med god noggrannhet kunna reproducera naturbundna dräneringsför­lopp och flöden i svackdiken, förutsatt tillbörlig kalibrering. God överensstämmelse (NSE>0.8) framkom inte bara mellan uppmätta och simulerade utgående hydrografer, utan också beträffande ändring av markfukthalt i ytligt marklager med snabb höjning av fukthalt upp emot full vattenmättnad. Däremot framkom endast mindre (eller total frånvaro av) överensstämmelse vad gäller markdjup av 0.2 m. Modellens output uppvisade låg käns­lighet för ursprunglig markfukthalt, speciellt gällande lågt flöde vilket resulterade i större residualer för simule­rade toppflöden och avrinningsvolymer. För fältförsöken framkom att den initiala markfukthaltens spatiala variabilitet inte påverkade utflödet från svackdiket – i motsats till noggrannheten i dikets topografiska repre­sentation. Denna uppsats belyser samband och följdverkningar beträffande påverkan från undersökta parametrar på en modell för flödes- och vattenföring i ett svackdike och framledes framtida design av svackdiken.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Desde o começo da formação dos conglomerados urbanos no Brasil, a drenagem urbana sempre teve uma abordagem sanitarista. Tal prática causa cada vez mais problemas como enchentes e eutrofização dos corpos d’água. Atualmente, os constantes problemas enfrentados pelas cidades retratam a forte situação de negligência em que se encontra este tema no país. Neste prisma, o presente projeto teve como objetivo propor um modelo Hidráulico/Hidrológico da rede de drenagem de Ilha Solteira, a fim de subsidiar decisões futuras de gestão da bacia urbana como um todo. A área de estudo foi a sub-bacia do córrego Sem Nome localizado na cidade de Ilha Solteira-SP. A base de dados utilizada foi obtida por meio de estudos disponibilizados pela prefeitura, ensaios de campo e a instalação de sondas e pluviógrafos na área de projeto. Além disso, foram usadas imagens de satélite obtidas por meio do Software Livre Google EarthPro. Foram utilizados os softwares ArcGis 10 e o Storm Water Management Model (SWMM) para estabelecer um modelo digital representativo da bacia, por meio das equações de Saint-Venant 1D e da onda cinemática. Foi realizada uma análise de sensibilidade, além da calibração e validação do sistema. Os cálculos desta pesquisa tiveram por base 31 eventos ocorridos durante o desenvolvimento da mesma, e o modelo foi avaliado sob o escopo de cinco indicadores estatísticos. Os resultados mostraram que o modelo elaborado teve desempenho satisfatório, com coeficientes de eficiência de Nash-Sutcliffe médios de 0,69; indicador de concordância médio de 0,92; erro médio na vazão de pico equivalente à 21% e erro médio no tempo de pico igual a 2 minutos e 40 segundos.
Since the beginning of the formation of urban conglomerates in Brazil, the urban drainage has been taken a sanitary approach. This practice has caused more and more problems, such as flooding and eutrophication of streams. The constant problem faced by most cities is the strong neglect that lies in this country. In this perspective, the present work proposes a Hydraulic/hydrological model of the storm water network of Ilha Solteira, in order to support future subsidization of urban basin management as a whole. The study area was the sub-basin of the Sem Nome stream located in the city of Ilha Solteira-SP. The used database was obtained by city hall studies, field trials, probes and rain gauges installed in the project area; the satellite images were obtained by using the Free Software EarthPro., ArcGis 10 and Stormwater Management Model (SWMM), to establish a representative digital model of the basin using the Saint-Venant 1D equations and the kinematic waveform. Sensitivity, calibration and validity analyses of the system were performed, 31 events were captured and a model was evaluated by five statistic indicators. The results have shown that the elaborated model has presented a satisfactory performance with mean Nash-Sutcliffe efficiency coefficients of 0.69, index of agreement of 0,92, average error in peak flow equivalent to 21% and mean error with no peak time equal to 2 minutes and 40 seconds.

This research introduces an approach to develop IDF relations under the context of climate change. SDSM tool is used for spatial downscaling and GEV distribution is used for temporal downscaling of GCM data. Also an empirical relationship between the extreme rainfalls and daily maximum temperature is evaluated. Developed IDF relations are used for hydrological modelling to evaluate the combined impacts of climate change and land use change on the urban catchments and urban stormwater management.

While many studies have evaluated the hydrologic effects of bioretention at the site level, few have investigated the role bioretention plays when distributed throughout a watershed. This study aims to assess bioretention's effects on an urbanized watershed using two modeled scenarios: one where runoff from many land uses was routed through the practice, and another in which only runoff from large impervious areas was routed. Peak flows, volumes, and lag times from these models were compared to the watershed's current and predeveloped conditions. Both scenarios provided reductions in peak flows with respect to existing conditions for modeled storm events, sometimes to levels below the predeveloped condition. Neither case was able to reduce volumes to predevelopment levels; the option to treat impervious areas had a negligible effect on runoff volume. Both cases were able to extend lag times from the existing development condition. Based on these results, bioretention appears to have the capability to improve watershed hydrologic characteristics. Furthermore, only treating impervious areas could be a viable alternative when funds or space are limiting factors.
Master of Science

This work quantifies the impacts of urban development on groundwater storage and groundwater-surface water interactions using intensive data analysis and mathematical modeling. The monthly water balance for the period 2000-2009 for 65 Baltimore area watersheds was calculated using remote sensing data and the dense network of instrumented sites in this region. This analysis included estimation of spatially-distributed anthropogenic fluxes (water supply pipe leakage, lawn irrigation, and infiltration and inflow (I&I) of groundwater and stormwater into wastewater pipes) as well as natural fluxes of precipitation, streamflow, and evapotranspiration. Inflow fluxes of water supply pipe leakage and lawn irrigation were significant but small compared to precipitation, but I&I was approximately equal to gaged streamflow. Building on knowledge of the altered water balance, an integrated hydrologic model of the Baltimore metropolitan region was developed to quantify the impact of urban development on groundwater storage. The three-dimensional groundwater-surface water-land surface model ParFlow.CLM was implemented and a methodology to incorporate urban and hydrogeologic input datasets was developed. Using the model, the impacts of reduced vegetative cover, impervious surfaces, I&I, and other anthropogenic discharge and recharge fluxes were isolated. Removal of I&I led to the largest change in storage, and removal of impervious surface cover had the smallest effect. To investigate the relationship between pre-event water proportion, storage, and streamflow at small watershed scales spanning a gradient of urbanization, chemical hydrograph separation, hillslope numerical experiments, and simple dynamical systems analysis were utilized. From analysis of high-frequency specific conductance data, the pre-event water proportion of stormflow was found to be greatest for storms with higher total precipitation. Using the simple dynamical systems approach, watersheds with larger percentages of impervious surfaces were found to have the largest sensitivity of streamflow to changes in storage. HydroGeoSphere, a three-dimensional groundwater-surface water flow and transport model, was implemented in an idealized hillslope and showed that the relationship between streamflow and storage was clockwise hysteretic. Overall this work demonstrates the importance of infrastructure leakage on urban hydrologic systems and shows that pre-event water contributions of stormflow are primarily related to precipitation and not initial storage in urban watersheds.

Geology
M.S.
The Wissahickon Creek is an urban stream that runs through Montgomery and Philadelphia Counties and discharges to the Schuylkill River in Philadelphia. A majority of stream segments in the Wissahickon watershed are considered impaired by the USEPA due to sediment and nutrients. Total Maximum Daily Loads (TMDLs) were implemented in 2003 for nutrients (NO3-, PO43-, NO2-, and CBOD5) and siltation. A new TMDL for total phosphorus (TP) was proposed in 2015, despite minimal data on the effectiveness of the 2003 TMDLs. This new proposal was met with concern, suggesting more data must be collected to better understand impairment in the Wissahickon Creek. The purpose of this research was to study turbidity and nutrient responses to storm events, as storm events are known to contribute significant loads of both sediment and nutrients. Twelve sites were chosen for high frequency turbidity and water level monitoring along the Wissahickon Creek and one of its main tributaries, Sandy Run. These sites were selected around three of the major wastewater treatment plants (WWTPs) to determine the relative roles of WWTPs and overland flow as sources of turbidity and nutrients during storm events. The upstream site and first downstream site at each WWTP were monitored for nutrients during storms using high frequency loggers and ISCO automatic samplers. Stream assessments were done at each site to characterize in-stream physical parameters, bank vegetation, and algae cover. High frequency turbidity data suggests that the turbidity is locally sourced, as turbidity peaks at the same time as water level, or within an hour or two, at all sites regardless of storm size. Comparisons of the turbidity response with in-stream parameters and land cover helped determine that the main factor driving the turbidity response is discharge, although bank topping and impervious cover, particularly roads, may increase turbidity responses at some sites. Similarities in nutrient, turbidity, and conductivity responses upstream and downstream of the WWTPs strongly suggest that overland flow, not WWTP effluent, is the major source of nutrients and sediment during storm events. Finally, a strong relationship between total phosphorus and high turbidity suggests that only during high discharge events is there a significant increase in TP in the Wissahickon Creek. Results from this research identify the source of turbidity and nutrients to the Wissahickon Creek during storms as primarily coming from overland flow, that the primary factor controlling the turbidity response is discharge, with some secondary influence from over-banking and the contribution of roads to land use, and a close link between TP concentrations and sediment during storms in the stream.
Temple University--Theses

Although snow's behaviour is well known in rural contexts through a long standing and widespread network of measurement and recording, the specificity of existing urban datasets to where they were measured limits their applicability to other cities. In this study, snow measurements were performed in urban and suburban Montreal, Québec, Canada over the course of the winter of 2007-2008. Observations of density, depth and albedo showed general trends similar to those expected from rural snow but with density values closer to those measured in other urban studies. Snow properties were scaled up to the convective footprint of an eddy covariance flux tower. Convective fluxes showed little to no relationship with observed snow conditions. Snow evolution data was used in the validation of an offline version of the snow subroutine that is part of the ISBA land surface model. Best results were found for locations subjected to little or no disturbance. Worst results were found for highly disturbed locations.
Malgré que le comportement de la neige soit bien documenté en milieu rural grâce à des réseaux de mesure en place depuis longtemps, la complexité des milieux urbains fait en sorte que le transfert de données acquises dans une ville à une autre n'est pas justifiable. Dans le but de la recherche présentée dans cette thèse, des mesures de la couverture neigeuse ont été effectuées dans un quartier résidentiel de la ville de Montréal, Québec, Canada et dans une de ses banlieues au cours de la saison hivernale 2007-2008. Les tendances générales se comportent similairement à celles observées en milieu rural à l'exception que les valeurs de densité se rapprochaient plus de valeurs observées au cours d'autres études urbaines. Les propriétés de la neige ont alors été mises à l'échelle de la zone source convective d'équipements de mesure de flux énergétiques. Les flux convectifs n'ont pas montrés de signe d'une dépendance aux conditions de neige. La base de données de l'évolution des propriétés de la neige a également servi dans la validation d'une version autonome du modéle de neige faisant partie du modéle d'échange de surface ISBA. Les meilleurs résultats ont étés obtenus pour des endroits subissant le minimum de perturbations humaines. Les pires résultats découlent de la simulation d'endroits très dérangés.

Quantitative precipitation estimation (QPE) remains a key area of uncertainty in hydrological modeling, particularly in small, urban watersheds which respond rapidly to precipitation and can experience significant spatial variability in rainfall fields. Few studies have compared QPE methods in small, urban watersheds, and studies which have examined this topic only compared model results on an event basis using a small number of storms. This study sought to compare the efficacy of multiple QPE methods when simulating discharge in a small, urban watershed on a continuous basis using an operational hydrologic model and QPE forcings. The Research Distributed Hydrologic Model (RDHM) was used to model a basin in Roanoke, Virginia, USA forced with QPEs from four methods: mean field bias (MFB) correction of radar data, kriging of rain gauge data, uncorrected radar data, and a basin-uniform estimate from a single gauge inside the watershed. Based on comparisons between simulated and observed discharge at the basin outlet for a 6-month period in 2018, simulations forced with the uncorrected radar QPE had the highest accuracy, as measured by root mean square error (RMSE) and peak flow relative error, despite systematic underprediction of the mean areal precipitation (MAP). Simulations forced with MFB corrected radar data consistently and significantly overpredicted discharge but had the highest accuracy in predicting the timing of peak flows.
Master of Science
Estimating the amount of rain that fell during a precipitation event remains a key source of error when predicting how much stormwater runoff will be produced, particularly in small, urban watersheds which respond rapidly to precipitation and can experience significant spatial variability in rainfall distribution. Rainfall estimation in small, urban watersheds has received relatively little attention, and studies which have examined this topic have generally only examined a small number of discrete storm events. This study sought to compare the efficacy of multiple precipitation estimation methods when simulating discharge in a small, urban watershed on a continuous basis using an operational hydrologic model and precipitation inputs. The Research Distributed Hydrologic Model (RDHM), commonly used by the National Weather Service, was used to model a basin in Roanoke, Virginia, USA forced with rainfall estimates from four methods: mean field bias (MFB) correction of radar data, kriging of rain gauge data, uncorrected radar data, and a basin-uniform estimate from a single gauge inside the watershed. Based on comparisons between simulated and observed discharge at the basin outlet for a 6-month period in 2018, simulations forced with the uncorrected radar QPE had the highest accuracy, as measured by several performance statistics, despite systematic underprediction of actual precipitation. Simulations forced with MFB corrected radar data consistently and significantly overpredicted discharge but had the highest accuracy in predicting the timing of peak flows.

From the Proceedings of the 1989 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 15, 1989, University of Nevada, Las Vegas, Nevada
Bottom sediments from several urban lakes located in the Phoenix metropolitan area were collected and analyzed for organic priority pollutants. The lakes selected for analysis were broadly representative of the diversity of lake characteristics found in the Phoenix area. That is, lakes were sampled that had different types of primary water sources and that were located in watersheds of differing degrees of urbanization. Preliminary results indicate that only nine of the 114 listed organic priority pollutants were found in measurable quantities in the sediments of the lakes surveyed. The pollutants detected were either phthalate esters or volatile or semi-volatile halogenated compounds. None of the pollutants were common to all the lakes sampled. Dibutyl phthalate was detected in three of the six lakes. A larger database is being developed and will be necessary to determine whether a statistical correlation exists between watershed characteristics and feedwater, and organic composition of lake sediments.

Includes bibliographical references
Despite the abundance of fresh water produced in the mountains surrounding Cape Town, a range of factors contribute towards the imminent water crisis felt locally and internationally. While governing bodies have management strategies and infra structural upgrades planned, these interventions address issues of water quantity only. Steadily declining water quality is an equally important issue which will continue to impact on available fresh water quantities if action is not taken. The threats on water availability in cities stem from growing urbanization itself. The question this dissertation poses is how architecture can encourage a symbiotic relationship between built and natural environments, with special regard for urban water systems. The answer is found in the balance of quantity management, quality improvement and long-term protection of water - a symbiosis between city and urban hydrology. This dissertation documents the research and design of a speculative architectural proposition to embody such a symbiosis. It is hypothesized that the design must address quantity and quality issues simultaneously by coupling infrastructure with community facilities. This will ensure immediate remediation of a water system and encourage a long-lasting protection of water quality through passive education and public conscientizing. The research identifies the Lotus River, located near the Philippi Horticultural Area in Cape Town, as an appropriate representative of the urban hydrological cycle in Cape Town. Through an understanding of the major pollutants in the river and a study of current technology, an industrial process which recycles pollution into fertilizer is proposed as the major programme of the project. This programme is overlaid with an agricultural training center and public amenities which encourage and incentivise environmental awareness among the community. The architectural theories of symbiosis and the social' condenser are proposed as precedent for the way in which architecture has, through the creation of transitional spaces, attempted to usher society into a new way of living. This project explores the creation of a transitional space between building and nature to encourage a symbiotic relationship between urbanity and water, where the Lotus meets the Machine.

Projections of population growth, urban expansion and decreasing water resources in arid and semi-arid regions have increased the importance of urban runoff as a potential renewable water resource that, through enhanced recharge, can augment groundwater supplies. However, it is unclear how urbanization alters hydrologic and hydrochemical responses of small catchments ( < 5 km²) in these regions. This body of work identified controls on the spatial and temporal variability of hydrologic and hydrochemical responses of urbanized catchments in the Tucson Metropolitan area of semi-arid southern Arizona. The temporal distribution and characteristics of rainfall did not control urban catchment hydrology where overall, there was no evidence of significant seasonal catchment wetting. Land use did not control hydrologic responses although runoff was more frequent and of longer duration in urbanized than in non-urban catchments. Runoff depth and runoff ratios were controlled by the combined effect of imperviousness, the characteristics of the stormwater drainage system and rainfall depth. Runoff hydrochemistry did not vary in response to land cover or imperviousness. Rapid increases in solute stores between rainfall-runoff vents resulted in invariant seasonal runoff solute concentrations. Four major factors controlling runoff hydrochemistry were identified: 1) landscape heterogeneity and catchment connectivity, 2) the spatial extent of pervious and biogeochemically active areas, 3) the efficiency of overland flow and runoff routing mobilization and 4) the extent of catchment wetting. The stormwater drainage system, and specifically the characteristics of the stream channel substrate, emerged as significant controls of runoff responses. Conservative transport of biogeochemically active solutes during runoff was observed in piped, concrete and gravel lined waterways, whereas solute sourcing and retention was more dynamic in grass lined reaches. Biogeochemical processing in the stream channel substrate between runoff events indicates that pervious waterways alter soil solute pools available for subsequent solute transport, and that stream channel biogeochemical processes are tightly linked to the characteristics of the channel substrate and cyclical channel wetting and drying. This body of work indicates that successful stormwater management strategies in the semi-arid Southwest should focus on the stormwater drainage network and the presence, density and characteristics of pervious channels.

As the world becomes more urbanized and heavy precipitation events increase in frequency and intensity, urban flooding is an emerging concern. Urban flooding is caused when heavy rainfall collects on the landscape, exceeding the capacity of drainage systems to effectively convey runoff. Unlike riverine and coastal flooding, urban flooding occurs frequently, and its risks and impacts are not restricted to areas within floodplains or near bodies of water. The objective of this dissertation is to improve our understanding of urban flooding and our capability to predict it through the development of tools and knowledge to assist with its analysis, modeling, and forecasting. To do this, three research objectives were fulfilled. First, the Stream Hydrology And Rainfall Knowledge System (SHARKS) app was developed to improve upon existing real-time hydrologic and meteorological data retrieval/visualization platforms through the integration of analysis tools to study the hydrologic processes influencing urban flooding. Next, the ability to simulate the hydrologic response of urban watersheds with large storm sewer networks was compared between the fully distributed Gridded Surface/Subsurface Hydrologic Analysis (GSSHA) model and the semi-distributed Storm Water Management Model (SWMM). Finally, the Probabilistic Urban Flash Flood Information Nexus (PUFFIN) application was created to help users evaluate the probability of urban flash flooding and to identify specific infrastructure components at risk through the integration of high-resolution quantitative precipitation forecasting, ensemble forecasting, and hydrologic and hydraulic modeling. The outcomes of this dissertation provide municipalities with tools and knowledge to assist them throughout the process of developing solutions to their site-specific urban flooding issues. Specifically, tools are provided to rapidly analyze and respond to rainfall and streamflow/depth information during intense rain events and to perform retrospective analysis of long-term hydrological processes. Evaluations are included to help guide the selection of hydrologic and hydraulic models for modeling urban flooding, and a new proactive paradigm of probabilistic flash flood guidance for urban areas is introduced. Finally, several potential directions for future work are recommended.
Doctor of Philosophy
As the world becomes more urbanized and heavy precipitation events increase in frequency and intensity, urban flooding is an emerging concern. Urban flooding is caused when heavy rainfall collects on the landscape, exceeding the capacity of drainage systems to effectively convey runoff. Unlike riverine and coastal flooding, urban flooding occurs frequently, and its risks and impacts are not restricted to areas within floodplains or near bodies of water. The objective of this dissertation is to improve our understanding of urban flooding and our capability to predict it through the development of tools and knowledge to assist with its analysis, modeling, and forecasting. To do this, three research objectives were fulfilled. First, the Stream Hydrology And Rainfall Knowledge System (SHARKS) app was developed to improve upon existing real-time hydrologic and meteorological data retrieval/visualization platforms through the integration of analysis tools to study the hydrologic processes influencing urban flooding. Next, the ability to simulate the hydrologic response of urban watersheds with large storm sewer networks was compared between the fully distributed Gridded Surface/Subsurface Hydrologic Analysis (GSSHA) model and the semi-distributed Storm Water Management Model (SWMM). Finally, the Probabilistic Urban Flash Flood Information Nexus (PUFFIN) application was created to help users evaluate the probability of urban flash flooding and to identify specific infrastructure components at risk through the integration of high-resolution quantitative precipitation forecasting, ensemble forecasting, and hydrologic and hydraulic modeling. The outcomes of this dissertation provide municipalities with tools and knowledge to assist them throughout the process of developing solutions to their site-specific urban flooding issues. Specifically, tools are provided to rapidly analyze and respond to rainfall and streamflow/depth information during intense rain events and to perform retrospective analysis of long-term hydrological processes. Evaluations are included to help guide the selection of hydrologic and hydraulic models for modeling urban flooding, and a new proactive paradigm of probabilistic flash flood guidance for urban areas is introduced. Finally, several potential directions for future work are recommended.

From the Proceedings of the 1987 Meetings of the Arizona Section - American Water Resources Association, Hydrology Section - Arizona-Nevada Academy of Science and the Arizona Hydrological Society - April 18, 1987, Northern Arizona University, Flagstaff, Arizona

The response of a karst aquifer to storm events is often faster and more severe than that of a non-karst aquifer. This distinction is often problematic for planners and municipalities, because karst flooding does not typically occur along perennial water courses; thus, traditional flood management strategies are usually ineffective. The City of Bowling Green (CoBG), Kentucky is a representative example of an area plagued by karst flooding. The CoBG, is an urban karst area (UKA), that uses Class V Injection Wells to lessen the severity of flooding. The overall effectiveness, siting, and flooding impact of Injection Wells in UKA’s is lacking; their influence on groundwater is evident from decades of recurring problems in the form of flooding and groundwater contamination. This research examined Class V Injection Wells in the CoBG to determine how Injection Well siting, design, and performance influence urban karst hydrology. The study used high-resolution monitoring, as well as hydrologic modeling, to evaluate Injection Well and spring responses during storm and baseflow conditions. In evaluating the properties of the karst aquifer and the influences from the surrounding environment, a relationship was established between precipitation events, the drainage capacity of the Injection Wells, and the underlying karst system. Ultimately, the results from this research could be used to make sound data-driven policy recommendations and to inform stormwater management in UKAs.

Conceptual urban runoff (CUR) models are commonly used in the Planning and design of urban drainage systems. These models often require a large number of variables and parameters in order to accurately describe, the complex relationships between rainfall, runoff and watershed characteristics. This requirement has often become a barrier to the use of such models, because of the difficulties involved in the estimation of these parameters. Hence, there is a great need to develop a robust and reliable automatic calibration procedure to assist in the identification of the best set of optimal parameters for a CUR model. The present study is therefore concerned with the automatic calibration of a typical and well-known CUR model, the U.S. Environmental Protection Agency Storm Water Management Model, or SWMM.
In this study, two automatic calibration methods were considered based an two different optimization algorithms: the Downhill Simplex (DHS), a popular local optimization technique, and the Shuffled Complex Evolution (SCE), a global optimization procedure. The consistency of SCE in estimating the SWMM model parameters was assessed under two different scenarios: (1) using "error-free" synthetic data, and (2) using observed data available an the Upper Bukit Timah catchment in Singapore. (Abstract shortened by UMI.)

The weight ratio of naturally occurring chloride and bromide (Cl/Br) can be used to identify water origin, and as a tracer. In the Tucson basin, where geologic inputs of these constituents are limited, the mean Cl/Br ratio of uncontaminated ground water is 130. This ratio may be altered by artificial recharge, sewage effluent disposal, and agricultural practices. In this study, Cl/Br ratios of 30 Tucson urban runoff samples averaged 34, one quarter that of the ground water. Cl/Br ratios may be useful in studying the fate of urban runoff recharged via dry wells. Urban runoff contains bromide from ethylene dibromide in leaded gasoline. Both species behaved conservatively in sorption and volatilization experiments; thus, these processes should not significantly alter Cl/Br ratios in surface or ground water. Bromide analytical methods were compared and methods best suited for analysis of dilute natural waters are discussed.

Green Stormwater Infrastructure (GSI) has become a popular method for flood mitigation as it can prevent runoff from entering streams during heavy precipitation. In this study, a recently developed neighborhood in Gresham, Oregon hosts a comparison of various GSI projects on runoff dynamics. The study site includes dispersed GSI (rain gardens, retention chambers, green streets) and centralized GSI (bioswales, detention ponds, detention pipes). For the 2017-2018 water year, hourly rainfall and observed discharge data is used to calibrate the EPA's Stormwater Management Model to simulate rainfall-runoff dynamics, achieving a Nash-Sutcliffe efficiency of 0.75 and Probability Bias statistic of 3.3%. A synthetic scenario analysis quantifies the impact of the study site GSI and compares dispersed and centralized arrangements. Each test was performed under four precipitation scenarios (of differing intensity and duration) for four metrics: runoff ratio, peak discharge, lag time, and flashiness. Design structure has significant impacts, reducing runoff ratio 10 to 20%, reducing peak discharge 26 to 68%, and reducing flashiness index 56 to 70%. There was a reverse impact on lag time, increasing it to 50 to 80%. Distributed GSI outperform centralized structures for all metrics, reducing runoff ratio 22 to 32%, reducing peak discharge 67 to 69%, increasing lag time 133 to 500%, and reducing flashiness index between 32 and 62%. This research serves as a basis for researchers and stormwater managers to understand potential impact of GSI on reducing runoff and downstream flooding in small urban watersheds with frequent rain.

From the Proceedings of the 1988 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 16, 1988, University of Arizona, Tucson, Arizona
A preliminary survey of several urban lakes in the Phoenix metropolitan area was undertaken to assess the degree of accumulation of priority pollutant metals and petroleum -based hydrocarbons in these impoundments. Three sediment samples were collected from each lake along a transect (from a probable point of stormwater addition to the opposite shore), and were composited on an equal weight basis prior to analysis. Total petroleum hydrocarbon concentrations ranged from 30 to 8000 mg /kg dry weight. The concentration ranges (mg /kg dry weight) of total metals were: arsenic 7-26, copper 25-2800, chromium 14-55, nickel 5-40, lead < 1-138, selenium < 0.5-1.1, and zinc 33-239. Silver and cadmium were undetectable (< 5.0 and < 0.5 mg /kg, respectively). Factors that may be associated with the magnitude of accumulation in urban lakes include lake age, primary source of influent, reception of stormwater runoff, mechanical aeration of the water, and direct chemical addition.

From the Proceedings of the 1985 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 27, 1985, Las Vegas, Nevada
Hydrologic and hydraulic design procedures developed by the Pima County Department of Transportation and Flood Control District were proposed for use by the Department of Transportation, Engineering Division of the City of Tucson, Arizona. These procedures were evaluated with respect to their reasonableness of approach and in comparison with other methods and existing data used to derive similar methodology and standards. The proposed criteria/methodology were found to be consistent with procedures used in other cities in the Southwest, and with the current state of the art in urban hydrology and hydraulic engineering practices and procedures. However, locally derived rainfall intensity -duration relationships were found to be superior to regionally based relationships, and minor modifications were suggested for channel design procedures.

The environmental issues of storm water in the urban environment is addressed in political policies on many different governance levels. The concept of “sustainable storm water” in Europe uses the natural water cycle as a template for urban drainage, and the EU has a water framework directive (WFD) with a systems approach, using drainage basins as the starting point of all actions. In Stockholm, a new storm water strategy was adopted in 2015 with a sustainability approach, using much of the terminology from the WFD and the Swedish Water & Wastewater Association. To find new aspects related to sustainable development of storm water management in Stockholm, this study used a resilience framework of seven principles to analyse the implementation of the Stockholm storm water strategy (SSWS). A mixed method approach was used for a qualitative study, using interviews and a review of policy documentation as the main data sources, complemented by a desk study of literature on the subject of storm water management, as well as participation in some relevant workshops. To broaden the study, examples from a developing area within the Stockholm municipality, Stora Sköndal, was used, as well as another municipality in the Baltic Sea region; Helsinki (Finland). The SSWS leans on the legislation of the environmental quality standards (EQS) but is lacking in authority coordination on a national and municipal level in Stockholm. Diversity in problem formulations and solutions for infrastructure is high, so is the diversity of involved stakeholders, which is an indication of resilience. This in combination with the structure and communicational links having questionable functionality, leads to a complex and inefficient structure in management of storm water, which undermines the resilience of the system. However, since the SSWS and other connected policies (such as local programmes of measures and sustainability requirements) are new, the system is undergoing change, which shows some level of adaptability and complex adaptive systems (CAS) thinking, another resilience indicator. The implementation of the WFD on a municipal level is also connected to CAS thinking, as well as a polycentric governance system -one of the seven resilience principles of the framework used. Some of the main issues found within this study for building resilience in the SES are related to follow-up and responsibility division.
Miljöfrågor inom dagvatten hanteras i policyarbete på flera olika institutionella nivåer. Begreppet ”hållbart dagvatten” utgår i Europa från den naturliga vattencykeln och EU:s vattendirektiv (WFD) har en systeminriktning som utgår från avrinningsområden istället för andra geografiska gränsdragningar. Stockholms Stad antog en ny dagvattenstrategi 2015 med en hållbarhetsinriktning, som innehåller mycket terminologi från WFD och publikationer från branchorganisationen Svenskt Vatten AB. För att hitta nya aspekter för en hållbar utveckling av dagvattenhantering i Stockholm använder denna studie ett teoretiskt ramverk inom resiliens,, som bygger på sju principer, i en analys av stadens dagvattensstrategi (SSWS). Blandade metoder användes för att genomföra en kvalitativ studie, där policydokument granskades tillsammans med intervjuer av nyckelpersoner, vilket kompletterades med en skrivbordsstudie av litteratur om dagvattenhantering samt deltagande i relevanta workshops. För att bredda studien användes exempel från ett planprogramsområde inom Stockholms kommun, Stora Sköndal, liksom en annan kommun i Östersjöområdet; Helsingfors (Finland). SSWS bygger juridiskt på miljökvalitetsnormerna, men brister i myndighetssamordning på nationell och kommunal nivå i Stockholm. Problemformuleringar och infrastrukturlösningar har hög mångfald, precis som involverade aktörer, vilket är en indikation på att systemet bygger upp resiliens. Detta i kombination med att struktur och kommunikationslänkar är något bristfälliga leder till en komplex och ineffektiv dagvattenhantering, vilket underminerar resiliensen i systemet. Eftersom SSWS och andra relaterade styrdokument (t.ex. lokala åtgärdsprogram och hållbarhetskrav) är nya, genomgår systemet förändringar, vilket visar på anpassningsförmåga och komplext, adaptivt systemtänk (CAS), vilket är en ytterligare resiliensindikator. Implementeringen av WFD på kommunal nivå är också kopplad till CAS-tänkande, liksom ett polycentriskt styrsystem - en av de sju principerna för resiliens i det teoretiska ramverket som används. Några av de huvudsakliga problem för att bygga resiliens som hittades i denna studie är relaterade till uppföljning och ansvarsfördelning.

Stroubles Creek is registered on Virginiaâ s 303(d) list of impaired waters for both benthic and fecal coliform impairments. The upper reach of the creekâ s watershed drains into two ponds on the Virginia Tech campus. The area draining to the ponds, approximately 715 acres, encompasses most of the Town of Blacksburg and the Virginia Tech campus. Below the ponds, the creekâ s watershed is primarily forested and agricultural, with some areas of residential development. In order to improve water quality downstream, the two ponds will be converted to a water quality facility by redirecting all flow from the northern branch of Stroubles Creek into the upper, smaller pond, which then flows into the larger pond below. With flow into the upper pond increasing dramatically, the dam between the two ponds and associated overflow structures were evaluated and redesigned to protect the dam from overtopping and possible washout. In addition, concrete weirs were designed and will be constructed on both branches of Stroubles Creek above the ponds for future installation of flow and water quality monitoring equipment. Above the ponds, the banks along both branches of the creek have become severely eroded. Interlocking concrete block armoring was designed for the stream banks to reduce erosion and protect the trees growing along the creek. This project was jointly funded by Virginia Tech and a grant from the Virginia Department of Conservation and Recreation Water Quality Improvement Fund. Construction will be performed by the Capital Design department of Virginia Tech.
Master of Science

Stream and watershed restoration projects have become increasingly common throughout the U.S., and the need for systematic post-project monitoring and assessment is apparent. This study describes three stream and watershed ecological restoration projects and the monitoring and evaluation methods employed or planned to evaluate project successes or failures. The stream and watershed restoration and evaluation methods described in this paper may be applicable to projects of similar types and scales. Rivers and streams serve a variety of purposes, including water supply, wildlife habitat, energy generation, transportation and recreational opportunities. Streams are dynamic, complex systems that not only include the active channel, but also adjacent floodplains and riparian vegetation along their margins. A natural stream system remains stable while transporting varying amounts of streamflow and sediment produced in its watershed, maintaining a state of “dynamic equilibrium.” (Strahler 1957, Hack 1960). When in-stream flow, floodplain morphology, sediment characteristics, or riparian vegetation are altered, this can affect the dynamic equilibrium that exists among these stream features, causing unstable stream and floodplain conditions. This can cause the stream to adjust to a new equilibrium state. This shift may occur over a long time and result in significant changes to water quality and stream habitat. Land-use changes in a watershed, stream channelization, installation of culverts, removal or alteration of streambank vegetation, water impoundments and other activities can dramatically alter ecological balance. As a result, large adjustments in channel morphology, such as excessive bank erosion and/or channel incision, can occur. A new equilibrium may eventually be reached, but not before the associated aquatic and terrestrial environment are severely impaired. Stream restoration is the re-establishment of the general structure, function and self-sustaining characteristics of stream systems that existed prior to disturbance (Doll et al. 2003). It is a holistic approach that requires an understanding of all physical and biological processes in the stream system and its watershed. Restoration can include a broad range of activities, such as the removal or discontinuation of watershed disturbances that are contributing to stream instability; installation of control structures; planting of riparian vegetation to improve streambank stability and provide habitat; and the redesign of unstable or degraded streams into properly functioning channels and associated floodplains. Kauffman et al. (1997) define ecological restoration as the reestablishment of physical, chemical and biological processes and associated linkages which have been damaged by human actions.

Washington, D.C., like many older U.S. cities, suffers the woes of rapid urbanization and aging infrastructure. The cityâ s combined sewer and stormwater system dumps millions of gallons of raw sewage into the Anacostia and Potomac Rivers over 70 times annually during significant rain events. While many groups, both public and private, attempt to clean the river, billions of dollars are still necessary over several years to remedy the combined sewer overfl ow (CSO) problem alone. Current plans for a solution include constructing large underground storage tanks that store millions of gallons of wastewater during overflow periods. Washington, however, once had a network of waterways that naturally drained the Federal City. At least three major stream systemsâ the Tiber Creek, James Creek and Slash Runâ and over 30 springs flowed within the boundaries of the emerging capital. The waterways, now buried, were victims of urbanization, and flow now only underground, wreaking havoc on foundations and basements and causing sewer backups and flooding. Can a historically-driven investigation of these buried channels lend credence to the resurrection in some form of a network of surface stormwater channels, separate from the municipal sewage system, to solve the cityâ s sewage overflow crisis? The following study is an initial exploration of the re-establishment of waterways through Washington with the purpose of improving the current storm sewer overflow dilemma and exploring the potential urban amenities that they could provide as part of a stormwater management plan for the year 2110.
Master of Landscape Architecture

Les contours théoriques en hydrologie, hydraulique et les outils de calcul correspondants sont largement développés et utilisés dans le monde. Cependant en parallèle, des problématiques importantes surviennent pendant les crises sans pouvoir être résolues et des solutions développées peinent à être implémentées. En plus, le changement climatique ne va pas faciliter les choses. Pour noircir le tableau, les moyens économiques locaux en France ne vont pas augmenter pour aider les communes à s’attaquer au problème. L’objectif de cette thèse est de conduire une investigation des moyens à disposition pour améliorer notre connaissance locale des concepts en lien avec le pluvial pour permettre une modélisation efficiente. La méthodologie proposée est composée de trois étapes évolutives incluant : 1. Une analyse approfondie des données topographiques locales ; 2. L’évaluation des interactions entre les écoulements de surface et le souterrain ; 3.Une approche intégrée permettant de modéliser les inondations générées par la pluie en zone urbanisée. Les résultats de l’étape 1 montrent que la donnée topographique est essentielle pour la définition des chemins d’écoulement et impactent significativement les résultats de modélisation hydrauliques. Ceci conduit à l’étape 2 lors de laquelle on observe que les débordements provenant du réseau souterrain contribuent à l’inondation mais seulement en partie. Les volumes d’inondations générés par le ruissellement de surface devraient être inclus dans les modèles d’inondation. L’étape 3 présente une configuration possible de modèle intégré permettant de mieux représenter les processus réels en jeu
Theoretical background about hydrology, hydraulics and computational tools and methods are widely developed and worldwide used. In the same time however, important issues during flood crisis are not solved and practical solutions take time to be implemented. On top of that, ongoing climatic change will not make things easier and intense events will increase in frequency. To worsen the picture, local economic means in France will not increase to help municipalities and local communities to tackle the issue. The objective of this thesis is to investigate on the available ways to improve our local knowledge of stormwater related concepts to allow an efficient modelling. The proposed methodology consists in a three-step-approach including: 1. A thorough analysis of local topography data; 2. The assessment of sewer-surface interactions; 3. An integrated approach to model pluvial flood in urban areas. The results of Step 1 show that topography data is essential in flow path definition and significantly impacts hydraulic modelling results. This leads to Step 2 where it is seen that sewer overflow is one aspect of urban flood issues but represents only part of flood sources. Overland flow generated by runoff should be included in flood models. Then Step 3 presents that integrated urban pluvial modelling is possible with existing tools and can represent the real processes better. This proposed modelling approach should not be disconnected from the reality of stormwater management practical aspects and current constraints. It is shown how complementary actions can be taken to enrich local knowledge and memory thus allowing a more efficient and wiser modelling process

The responsibility for mitigation of the ecological effects of urban stormwater runoff has been delegated to local government authorities through the Clean Water Act's National Pollutant Discharge Elimination Systems' Stormwater (NPDES SW), and Total Maximum Daily Load (TMDL) programs. These programs require that regulated entities reduce the discharge of pollutants from their storm drain systems to the "maximum extent practicable" (MEP), using a combination of structural and non-structural stormwater treatment — known as stormwater control measures (SCMs). The MEP regulatory paradigm acknowledges that there is empirical uncertainty regarding SCM pollutant reduction capacity, but that by monitoring, evaluation, and learning, this uncertainty can be reduced with time. The objective of this dissertation is to demonstrate the existing sources and magnitude of variability and uncertainty associated with the use of structural and non-structural SCMs towards the MEP goal, and to examine the extent to which the MEP paradigm of iterative implementation, monitoring, and learning is manifest in the current outcomes of the paradigm in Virginia. To do this, three research objectives were fulfilled. First, the non-structural SCMs employed in Virginia in response to the second phase of the NPDES SW program were catalogued, and the variability in what is considered a "compliant" stormwater program was evaluated. Next, the uncertainty of several commonly used stormwater flow measurement devices were quantified in the laboratory and field, and the importance of this uncertainty for regulatory compliance was discussed. Finally, the third research objective quantified the uncertainty associated with structural SCMs, as a result of measurement error and environmental stochasticity. The impacts of this uncertainty are discussed in the context of the large number of structural SCMs prescribed in TMDL Implementation Plans. The outcomes of this dissertation emphasize the challenge that empirical uncertainty creates for cost-effective spending of local resources on flood control and water quality improvements, while successfully complying with regulatory requirements. The MEP paradigm acknowledged this challenge, and while the findings of this dissertation confirm the flexibility of the MEP paradigm, they suggest that the resulting magnitude of SCM implementation has outpaced the ability to measure and functionally define SCM pollutant removal performance. This gap between implementation, monitoring, and improvement is discussed, and several potential paths forward are suggested.
Ph. D.

Geology
M.S.
Vacant lots in cities and surrounding urban areas can potentially be used for stormwater management because they are pervious. However, the extent to which vacant lots provide pervious cover to increase infiltration and reduce stormflow is poorly understood. The goal of this study was to develop faster methods for monitoring stormwater infiltration to improve characterization of heterogeneous urban systems. Geophysical techniques are capable of mapping and characterizing subsurface materials, but are often limited by time and sensitivity constraints. In this study, the infiltration characteristics of a vacant lot created by the demolition of a house was characterized using a series of modeling, field and lab experiments. Site characterization under background conditions with an EM Profiler was used to map zones of different fill materials. Three zones were identified in the study site: grass area, driveway area, and a former house area. Transient soil moisture conditions were monitored during irrigation tests using two geophysical methods (electrical resistivity tomography [ERT] and electromagnetic induction [EM]) to evaluate method sensitivity and differences between the three zones. ERT proved more sensitive than EM profiling at detecting changes in the three zones. Soil moisture changes in the driveway area were particularly difficult to detect using EM. The EM Profiler showed a reduction rather than increase in conductivity at the start of irrigation and storms, which was attributed to flushing of high conductivity pore fluids by dilute irrigation or rain water. This explanation was supported using Archie’s Law to model the response of apparent conductivity under highly conductive pore fluid conditions. The EM Profiler was also used under natural precipitation conditions to quickly monitor areas too large for the ERT to reasonably survey. The results suggested that EM instrument drift needs to be corrected to make the method more sensitive. It was difficult to detect differences in hydrologic characterization between areas of the vacant lot using traditional soil point measurements because of the inherent spatial variability. The most useful point measurement was soil moisture loggers. Data from soil moisture loggers was used to parameterize the model; in addition, the soil moisture loggers showed a slow drying period. By combining the EM Profiler method with soil moisture data and applying corrections for drift, some improvement in sensitivity might be achieved. Quantitative characterization of fill material was shown by ERT, which detected more heterogeneous infiltration in the area of the former house than in the grass area.
Temple University--Theses

Thesis (M.ScEng.)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: Historically, urban waterresources have too often been managed without recognition that the flow in a river integrates many landscape and biological features. This has often resulted in the elimination of natural processes and their replacement by man-made streamlined structures with the effects of increased urbanisation being primarily addressed from an engineering and economics point of view to the detriment of environmental and social issues. Catchment Management, as legislated in the Water Act, No. 36 of 1998, is a management approach to address the negative consequences of an urban stormwater design philosophy restricted to flood restriction. It is a systems approach that integrates engineering and scientific skills, socio-economic concerns, and environmental constraints within a new multidisciplinary decision-making process that recognises the different components of the hydrological and aquatic cycles are linked, and each component is affected by changes in every other component. In order to make effective management decisions, catchment managers require tools to provide reliable information about the performance of alternative arrangements of stormwater management facilities and to quantify the effects of possible management decisions on the water environment. A deterministic hydrological model is such a tool, which provides the link between the conceptual understanding of the physical catchment characteristics and the empirical quantification of the hydrological, water quality and ecological response. In order to provide effective computer based decision support, the hydrological model must be part of an integrated software application in which a collection of data manipulation, analysis, modelling and interpretation tools, including GIS, can be efficiently used together to manage a large potion of the overall decision process. This decision support system must have a simple and intuitive user interface able to produce easily interpreted output. It must have powerful graphical presentation capabilities promoting effective communication and be designed to solve ill-structured problems by flexibly combining statistical analysis, models and data. The Great Lotus River canal, situated on the Cape Flats, Cape Town, has been designed and controlled through extensive canalisation and the construction of detention pond facilities to avoid the flooding of urban areas of the catchment. This approach has resulted in these channels becoming stormwater drains, transporting waste and nutrients in dissolved and particulate forms, and reducing their assimilatory capacity for water quality improvement. In order to investigate the use of hydrological modelling in decision support for Catchment Management, the semi-distributed, physically based model, SWMM, was applied to the Great Lotus River canal. SWMM consists of a number of independent modules allowing the hydrological and hydraulic simulations of urban catchments and their conveyance networks on an event or continuous basis. In order to ease the application of the Fortran based SWMM model, the GUl, PCSWMM98, was developed by Computational Hydraulics Inc (CH!). This provides decision support for SWMM through large array of tools for file management, data file creation, output visualisation and interpretation, model calibration and error analysis and storm dynamic analysis thus easing any simulations with SWMM. In addition, PCSWMM was developed with a GIS functionality for graphically creating, editing and/or querying SWMM model entities and attributes, displaying these SWMM layers with background layers and dynamic model results, and exporting data to SWMM input files thus providing an interface between a GIS and SWMM. In terms of Catchment Management, the above DSS can be used effectively to assist decisionmaking. This is to address tensions between the fundamental catchment management considerations of physical development, social considerations and maintaining ecological sustainability. It is at the stages of Assessment and Planning that the model can play the most significant role in providing decision support to the Catchment Management process. Assessment in the Catchment Management process refers to the collection, storage, modelling and interpretation of catchment information. It is in this quantification, interpretation and assessment of catchment information that a hydrological model contributes to an increase in knowledge in the Catchment Management process. In identifying and quantifying, at a sufficient temporal and spatial scale, the dominant cause and effect relationships in the urban physical environment, a hydrological model is able to highlight the main contributing factors to an issue. This is used in the Planning stage of the Catchment Management process and when combining these contributing factors with assessments of the socio-economic and administrative environments, enables the prioritisation of the principal issues requiring attention in a Catchment Management Strategy. It is possible to link the multiple decision-making requirements of Catchment Management with the abilities of a hydrological model to provide information on these requirements in a conceptual framework. This framework consists of the fundamental catchment considerations of Physical Development, Environmental Management and Social Development and resolves these considerations into the various management issues associated with each consideration ~s well as its management solution. The management solutions are linked to the model through formulating the solution in terms of the model parameters and perturbing the affected parameters in ways to simulate the management solution. This results in model output and graphical interpretation of the effects of the suggested management solution. A comparison between the simulated effects of each management solution allows the Catchment Management body to identify optimal management solutions for the various management Issues. The present model of the Great Lotus River catchment is sufficient to simulate the overland and subsurface flows from individual parts of the catchment and to route these flows and associated pollutant loadings to the catchment outlet. At its present level of complexity, the finely discretised model subcatchment and conveyance network provides decision support for Catchment Management through the simulation, at a pre-feasibility stage, of various Catchment Management issues and their proposed solutions. Given more detailed canal and drainage network dimensions and water quality data, it is possible for the model to incorporate hydraulic calculation routines to assess the implications of alternative river rehabilitation techniques and waste management strategies. This would allow greater capability in assessing the role of the various BMPs in ameliorating stormwater impacts and pollutant loading. In addition, a detailed level survey of the stormwater pipe and canal network could result in hydrological modelling being utilised to identify critical areas where stormwater upgrading would be necessary. In order to facilitate future complex, finely discretised catchment hydrological models, it is imperative that complete and detailed drainage patterns and stormwater network characteristics are available. In addition, to minimise model generation costs and time of model setup, this spatially representative data must be captured in a GIS for rapid inclusion into the model. Furthermore, complete spatially representative precipitation datasets are necessary to ensure that model error is reduced. These two issues of available spatial data and comprehensive precipitation records are crucial for the generated models to function as effective decision support systems for Catchment Management.
AFRIKAANSE OPSOMMING: Histories is stedelike waterbronne te dikwels bestuur sonder inagneming dat die vloei van die rivier baie landskap- en biologiese kenmerke insluit. Dit het dikwels daartoe gelei dat natuurlike prosesse uitgeskakel is en vervang is deur mensgemaakte, stroombelynde strukture waarvan die effek van toenemende verstedeliking hoofsaaklik aangespreek word vanuit 'n ingenieurs- en ekonomiese oogpunt tot nadeel van omgewings- en sosiale kwessies. Opvangsgebiedsbestuur, soos bepaal deur die Waterwet, Wet 36 van 1998, is 'n bestuursbenadering om die negatiewe gevolge van 'n stedelike stormwaterontwerpfilosofie wat beperk is tot vloedbeperking aan te spreek. Dit is 'n stelselbenadering wat ingenieurs- en wetenskaplike vaardighede, sosio-ekonomiese probleme en omgewingsbeperkings integreer in 'n nuwe multidissiplinêre besluitnemingsproses wat erkenning daaraan gee dat die verskillende komponente van die hidrologiese en watersiklusse verbind is, en elke komponent beïnvloed word deur veranderings in elke ander komponent. Om doeltreffende bestuursbesluite te neem, benodig opvangsgebiedsbestuur die hulpmiddels om betroubare inligting oor die prestasie van alternatiewe moontlikhede VIr stormwaterbestuurfasiliteite en om die effek van moontlike bestuursbesluite op die wateromgewing te kwantifiseer. 'n Deterministiese hidrologiese model is so 'n hulpmiddel wat die skakel daarstel tussen die konseptueie begrip van die fisiese opvangsgebiedskenmerke en die empiriese kwantifisering van die water-, waterkwaliteit- en ekologiese reaksie. Om doeltreffende rekenaarbesluitnemingsteun te verskaf, moet die hidrologiese model deel wees van 'n geïntegreerde sagteware-aanwending waarin 'n versameling datamanipulasie-, analise-, modellerings- en interpreteringshulpmiddels, insluitend GIS, doeltreffend saam gebruik kan word om 'n groot deel van die algehele besluitnemingsproses te bestuur. Hierdie besluitnemingsteunstelsel moet 'n eenvoudige en intuïtiewe gebruikersvlak hê wat in staat is om maklik interpreteerbare uitsette te lewer. Dit moet goeie grafiese voorleggingsvermoëns hê wat doeltreffende kommunikasie vergemaklik en ontwerp wees om swak gestruktureerde probleme deur die buigsame samevoeging van statistiese analise, modelle en data op te los. Die Groot Lotusrivierkanaal op die Kaapse Vlakte, Kaapstad is ontwerp en word beheer deur uitgebreide kanalisasie en die konstruksie van detensiedamfasiliteite om die oorstroming van stedelike opvangsgebiede te vermy. Hierdie benadering het daartoe gelei dat hierdie kanale stormwaterafvoerpype geword het wat afval en nutriënte in opgelosde en partikelvorm vervoer en hulle assimilasievermoë vir die verbetering van waterkwaliteit verminder. Om die gebruik van hidrologiese modelle in besluitnemingsteun vir Opvangsgebiedsbestuur te ondersoek, is die semi-verspreide, fisiesgebaseerde model, SWMM, op die Groot Lotusrivierkanaal toegepas. SWMM bestaan uit 'n aantalonafhanklike modules wat die hidrologiese en hidroulika simulasies van stedelike opvangsgebiede en hulle vervoemetwerke per geleentheid of deurlopend monitor. Om die aanwending van die Fortran gebaseerde SWMM model te vergemaklik is die GUl, PCSWMM98 deur Computational Hydraulics Inc (CHD ontwikkel. Dit verskaf besluitnemingsteun vir SWMM deur 'n groot aantal hulpmiddels vir lêerbestuur, die skep van datalêers, uitsetvisualisering en interpretasie, modelkalibrasie, foutanalise en stormdinamikaanalise om enige simulasies met SWMM te vergemaklik. Daarby is PCSWMM ontwikkel met 'n GIS funksionaliteit vir die grafiese daarstelling, redigering en/of navraagfunksie van SWMM model entiteite en kenmerke, wat hierdie SWMM vlakke met agtergrondvlakke en dinamiese modelresultate vertoon en data in SWMM inset1êers plaas en op daardie manier 'n koppelvlak tussen 'n GIS en SWMM verskaf. Volgens Opvangsgebiedsbestuur kan bogenoemde DSS doeltreffend gebruik word in besluitneming. Dit IS om die spanning tussen fundamentele opvangsgebiedsbestuursoorwegings van fisiese ontwikkeling, sosiale oorwegings en ekologiese volhoubaarheid aan te spreek. Dis in die stadiums van Waardebepaling en Beplanning wat die model die belangrikste rol kan vervul in die verskaffing van besluitnemingsteun vir die Opvangsgebiedsbestuursproses. Waardebepaling in die Opvangsgebiedbestuursproses verwys na die versameling, berging, modellering en interpretasie van opvangsgebiedsinligting. Deur hierdie kwantifisering, interpretasie en waardebepaling van opvangsgebiedsinligting dra 'n hidrologiese model by tot 'n verhoging in kennis in die Opvangsgebiedsbestuur. Deur die identifisering en kwantifisering, op 'n ruim genoeg tydelike en ruimtelike skaal, van die dominante oorsaak en gevolg verhoudings in die stedelike fisiese omgewing, kan die hidrologiese model die hoof bydraende faktore uitlig. Dit word gebruik in die Beplanningsfase van die Opvangsgebiedproses en wanneer hierdie bydraende faktore by die waardebepaling van die sosio-ekonomiese en administratiewe omgewings saamgevoeg word, maak dit moontlik om die belangrike kwessies wat aandag behoort te kry in 'n Opvangsgebiedsbestuurstrategie in volgorde van voorrang te plaas. Dit is moontlik om die verskeidenheid besluitnemingsvereistes van Opvangsgebiedsbestuur met die vermoëns van 'n hidrologiese model te koppel om inligting oor hierdie vereistes in 'n konseptuele raamwerk te verskaf. Die raamwerk bestaan uit die fundamentele opvangsgebiedsoorwegings van Fisiese Ontwikkeling, Omgewingsbestuur en Sosiale Ontwikkeling en los hierdie oorwegings op in die verskillende bestuursaangeleenthede wat met elke oorweging en die bestuuroplossing geassosieer word. Die bestuursoplossings word aan die model gekoppel deur die formulering van die oplossing volgens die modelparameters en versteuring van die relevante parameters op sekere manier om die bestuursoplossing te simuleer. Dit lei tot modeluitset en grafiese interpretasie van die effek van die voorgestelde bestuursoplossing. 'n Vergelyking tussen die gesimuleerde effek van elke bestuursoplossing laat die Opvangsgebiedsbestuursliggaam toe om die optimale bestuursoplossings vir die verskeie bestuursaangeleenthede te identifiseer. Die huidige model van die Groot Lotusrivieropvang is genoegsaam om die bo- en ondergrondse vloei vanaf individuele dele van die opvangsgebied te simuleer en om die watervloei en geassosieerde besoedelstofladings na die opvangsgebiedsuitlaatplek te lei. Op sy huidige vlak van kompleksiteit verskaf die fyn gediskretiseerde model subopvangsgebied en vervoernetwerk besluitnemingsteun aan Opvangsgebiedsbestuur deur die simulasie, teen 'n voor-lewensvatbaarheidstudie, van verskeie opvangsgebiedsbestuurkwessies en die voorgestelde oplossings. Indien meer gedetailleerde kanaal- en dreineringsnetwerkdimensies- en waterkwaliteitdata ingevoer word, is dit moontlik vir die model om hidroulikaberekeningsroetines te inkorporeer om die implikasies van alternatiewe rivierrehabilitasietegnieke en afvalbestuurstrategieë te beoordeel. Dit sou die vermoë verbeter om die waarde van die verskeie BMPs te bepaal om die impak van stormwater en besoedelstoflading te versag. Daarby kan 'n gedetailleerde vlakopname van die stormwaterpyp en -kanaalnetwerk daartoe lei dat hidrologiese modelle gebruik kan word om kritieke areas te identifiseer waar stormwateropgradering nodig is. Om toekomstige komplekse, gediskretiseerde opvangsgebiedshidrologiese modelle te verbeter, is dit noodsaaklik dat volledige en gedetailleerde dreineringspatrone en stormwaternetwerkkenmerke beskikbaar is. Om die model-ontwikkelingskoste en tyd bestee aan die opstel van 'n model te minimiseer, moet hierdie ruimtelik verteenwoordigende data ingelees word in 'n GIS vir vinnige insluiting in die model. Daarbenewens is volledige, ruimtelik verteenwoordigende presipitasie datastelle nodig om te verseker dat modelfoute verminder word. Hierdie twee kwessies van beskikbare ruimtelike data en omvattende presipitasierekords is van die uiterste belang sodat die gegenereerde modelle as doeltreffende besluitnemingsteun vir Opvangsgebiedsbestuur kan funksioneer.

The objective of this study was to characterize water quality and hydrologic properties of urban streams in the Richmond metropolitan area. Water quality data were analyzed for six urban sites and two non-urban sites. Geomorphological surveys and conservative tracer studies were performed at four urban sites and one non-urban site to describe intra- and inter- site variability in transient storage, channel geomorphology, and related hydrologic parameters. Urban sites showed elevated concentrations of nitrogen and more variable TSS concentrations relative to reference sites. Urban channels were deeply incised with unstable banks and low sinuosity. Little Westham Creek exhibited the greatest transient storage. This site was characterized by large, deep pools and therefore it is likely that transient storage was associated with surface water storage. Transient storage was low at all other sites, particularly for the study reach at Reedy Creek, which flowed through a concrete channel. Lowest transient storage was observed at this site in spring, though higher values were measured in summer corresponding to the presence of biofilms, A lower, more naturalized section of the concrete channel was found to have greater transient storage suggesting the possibility of passive restoration of concrete channels in urban environments. This study documents variability in the structure and function of urban streams. Restoration projects should work to improve impairments that are specific to each site at both the reach and watershed scale to maximize the efficacy of restoration.

The change in the hydrological cycle due to climate change entails more frequent and intense rainfall. As a result, urban water systems will be disproportionately affected by the climate change, especially in such urban areas as Las Vegas, which concentrates its population, infrastructure, and economic activity. Understanding the proper management of urban stormwater in the changing climate is becoming a critical concern to the water resources managers. Proper design and management of stormwater facilities are needed to attenuate the severe effects of extreme rainfall events. In an effort to develop better management techniques and understanding the probable future scenario, this study used the high-resolution climate model data conjunction with advanced statistical methods and computer simulation. Las Vegas Valley which has unique climatic condition and is surrounded by the mountains in every direction was chosen for the study. The North American Regional Climate Change Assessment Program is developing multiple high-resolution projected-climate data from different combinations of regional climate models and global climate models. First, the future design depths was calculated using generalized extreme value method with the aid of L-moment regionalization technique. The projected climate change was incorporated into the model at the 100 year return period with 6h duration depths. Calculation showed that, the projection from different sets of climate model combinations varied substantially. Gridded reanalysis data were used to assess the performance of the climate models. This study used an existing Hydrologic Engineering Center’s Hydrological Modeling System (HEC-HMS) model and Storm Water Management Model (SWMM) developed by the Environmental Protection Agency (EPA) were implemented in the hydrological simulation. Hydrological simulation using HEC-HMS showed exceedances of existing stormwater facilities that were designed under the assumption of stationarity design depth. Low Impact Developments such as permeable pavement and green roof were found to be effective in the attenuation of climate change induced excess surface runoff. The primary purpose of this study is understanding of proper designing, planning and management of the urban stormwater system in the predicted climate scenarios.

The HYDROPAC model was developed to improve the technology transfer from the science of hydrology to environmental planning disciplines by initiating advanced spatial analysis techniques for predicting rainfall-runoff relationships. This model integrates the Soil Conservation Service (SCS) equations for calculating runoff and a Geographic Information System (Map Analysis Package) in a framework that allows the simulation of runoff processes over a digital elevation model. The simulations are done in discrete time steps allowing the generation of a hydrograph at any desired point in the watershed and the overland flow patterns are displayed in maps. This framework addresses some of the current limitations of hydrologic model for stormwater management planning in terms of capabilities for analysis and communication of results. This manuscript describes the methods used to develop the framework of the HYDROPAC model and its usefulness for analyzing potential runoff problems during the planning process.

This project proposes a new urban aquifer strategy that utilizes stormwater to create a cascading plaza and an improved 'great street' in Washington DC. A system of urban aquifers is developed beneath the surface of the street, perched atop the compacted, impermeable soils below. This set of aquifers prevents stormwater from entering the existing combined sewer and allows trees to draw water from this new groundwater source and develop expansive root systems. On the surface, stormwater flows through interconnected planters where it irrigates and is filtered by vegetation before infiltrating to recharge the aquifer. At Cascade Plaza, sloping topography intersects the aquifer, and the new groundwater seeps out of the plaza steps, turning them into a miniature cascade, by gravity and water pressure alone. It collects in a web of runnels, pools at the lowest point, and overflows in high water, mysteriously disappearing below ground again to fill an underground reservoir. In this unique ecological system, water flows both above and below ground to mitigate excess stormwater and make the street and plaza more beautiful.
Master of Landscape Architecture

Airborne multispectral video was evaluated as a tool for obtaining urban land cover information for hydrological simulations. Land cover data was obtained for a small urban watershed in Tucson, Arizona using four methods: multispectral aerial video (2 meter and 4 meter pixel resolution), National High Altitude Photography (NHAP), multispectral satellite imagery from Systeme Pour l'Observation de la Terre (SPOT), and by conventional survey. A semi-automated land cover classification produced four classes: vegetation, buildings, pavement, and bare soil. The land cover data from each classification was used as input to a runoff simulation model. Runoff values generate by each simulation were compared to observed runoff. A chi-square goodness-of-fit test indicated that SPOT produced landcover data most similar to the conventional classification. In the curve number model, the SPOT data produced simulated runoff values most similar to observed runoff.

Ytvattenkvaliteten kan förändras på grund av naturliga processer som vittring och erosion i mark och berggrund men den kan också förändras på grund av antropogen påverkan. Den största föroreningskällan som belastar svenska vattendrag kommer från diffusa utsläpp. Syftet med det här arbetet har varit att analysera och utvärdera samband mellan föroreningsspridning i ytvatten i förhållande till nederbörd och vattenflöde i en urban miljö. Fallstudieområdet är begränsat till Göta älv från Vänerns utlopp ner till Göteborgs stad. Med den rådande klimatförändringen kommer den globala medeltemperaturen att öka. Till följd av detta kan nederbördsmönster och mängden regn komma att förändras. Nederbördsmängden förväntas öka med ca 10-25 % i Västra Götaland mot slutet av det här seklet. Gömda föroreningskällor som legat i marken kan komma upp till ytan om grundvattennivåerna börjar fluktuera och ytavrinningen kan sedan ta med sig föroreningarna till vattendrag. Vattendrag i en urban miljö är mer utsatta för föroreningar på grund av närheten till föroreningskällorna. Uppmätta halter av metaller har analyserats och utvärderas i en korrelationsanalys mellan nederbördsmängd och mellan vattenföring. Vattenkvaliteten har också jämförts mellan de 10 mätstationer som finns placerade utmed Göta älv. Resultaten från studien visar att det reglerade vattenflödet i Göta älv har en avgörande betydelse för att identifiera samband. Inga samband kunde identifieras mellan reglerat vattenflöde och föroreningshalt. Däremot kunde ett svagt samband urskiljas mellan krom och oreglerat vattenflöde. Tydligast samband upptäcktes mellan ackumulerad tremånadsnederbörd och uppmätta metallhalter av krom, nickel och kobolt. Det beror sannolikt på förhöjda grundvattennivåer, ökad ytavrinning och ökade vattenflöden som lakar ur marken som innehåller dessa metaller. Förutom metallhalter påvisade turbiditeten ett tydligt samband mellan både ett oreglerat vattenflöde och en ackumulerad nederbörd. För att säkerställa de samband som har framkommit i denna studie behövs en längre tidsperiod av analysdata samt planerade mätningar för att täcka in och återspegla förändringar i nederbördsmängd och variationer i vattenföringen.
The surface water quality may change because of natural processes like weathering and erosion of the earth´s surface, but it can also change because of anthropogenic impact. The largest impacts on Swedish streams are diffuse emissions from landfills or contaminated areas and traffic. The aim of this study is to analyze and evaluate the possible relationship between the concentration of metals and precipitation and discharge. The study area is the river Göta älv, from the outlet of Lake Vänern down to the city of Gothenburg. With the current climate change, the global mean temperature will increase, which will cause changes in the precipitation, in terms of both intensity and volume. Precipitation is expected to increase by 10-25 % in the region of Västra Götaland towards the end of this century. Hidden sources of contaminations in the ground can rise to the surface if the groundwater levels start to fluctuate. Surface runoff can also bring contaminations from urban areas to the streams. If streams have an urban connection they can more easily be affected by contaminants because of the closeness to the source of contamination. Measured concentration of metals have been analyzed and evaluated in correlation analyses. The water quality has also been evaluated between the 10 gauging stations along the river Göta älv. The results from this study show the significance of stream regulation for identification of possible relationship. No relationships appeared in the first correlation between discharge of a regulated stream and metal concentration. However, a weak relationship was found between the concentrations of chromium and a non-regulated discharge. The clearest relationship was discovered in the correlation between the concentrations of chromium, nickel and cobalt and an accumulated three month precipitation. The explanation is most likely due to groundwater levels which fluctuate, increased surface runoff and increased discharge which flushes the metals out from the nearby ground. Except for the metals, turbidity has shown a clear relationship between both non-regulated discharge and accumulated precipitation. More data is needed to confirm these relationships and to ensure their meaning. For future studies it is important to plan the measurements so they can cover all the changes and the variability of precipitation and discharge.