Dissertations / Theses on the topic 'Flood mitigation'

Approved for public release; distribution is unlimited
Floods are the nation's greatest natural disaster. According to the U.S. Geological Survey, floods cause an average of $6 billion of property damage, claim 140 lives, and prompt more Presidential disaster declarations per year than any other hazard. The Federal Emergency Management Agency (FEMA) is the lead for federal response to natural disasters. FEMA was the lead agency in 1993 when floods caused an estimated $1 8 billion in damage in the Midwest. The scope and damages of this historic disaster led FEMA to change its approach to floodplain management, flood protection, flood mitigation, disaster response, and recovery. FEMA and federal emergency response further evolved following the terrorist attacks on September 11, 2001 and Hurricane Katrina in 2005. The latest changes resulted in a national response framework for all levels of government to prepare and respond to all natural and manmade hazards. In 2008, the Midwest experienced its second "500-year flood" in fifteen years. This thesis examines whether changes to national disaster response and investments in flood mitigation over the last fifteen years have improved preparation, protection, and response capabilities at the federal, state, and local levels.

Rainwater harvesting (RWH) in the UK has seen a low level of uptake relative to similar settings such as Australia and Germany. The relatively low cost of municipal water in the UK limits the financial savings associated with RWH systems, especially in a domestic setting. Although financial benefits can be relatively low (in terms of reduced water bills), academic and practitioner studies have demonstrated the potential for RWH to significantly reduce potable water demands at typical UK houses. Hence, increased uptake of RWH has potential to contribute to mitigating droughts in water scarce regions. Stormwater management in the UK is receiving increasing attention at all levels; from grass-roots sustainable drainage systems (SuDS) such as downpipe disconnections and raingardens; through to implementation of urban realm attenuation schemes and continued development of guidance from UK policy makers. The public realm nature of most SuDS presents a need for partnership approaches to be fostered between infrastructure mangers and the general public. The application of RWH as a technology within the SuDS management train has been limited in the UK as policy makers have taken the view that RWH tanks may be full at the start of a design storm, and thus the potential for attenuation and peak discharge reduction has been largely ignored. However, in the last few years there has been a shift in emphasis; from RWH perceived purely as a water demand management technology to a focus on its wider benefits e.g. mitigating surface water flooding through improved stormwater management. RWH systems examined in this thesis are now available which offer multiple benefits to both end-users and water service providers. The application of RWH in a dual purpose configuration (to displace potable water demands and control stormwater discharges) has seen increasing interest during the development of this thesis. However, the successful design of RWH as a stormwater management tool requires a series of calculations to be completed. To date, practitioners have frequently relied upon low-resolution heuristic methods which lead to a small range of configurations being deployed, with minimal demonstrable stormwater control benefits. In this thesis, full details of novel and traditional RWH technologies were identified and described. Empirical data was collected, both in laboratory conditions and at field sites, to identify the real world operating characteristics of a range of RWH configurations. Additionally a new time series evaluation methodology was developed to enable RWH systems to be designed and analysed. This method quantifies water demand benefits and also focusses on stormwater management metrics (i.e. largest annual discharge and total discharge volume per year). The method was developed to enable a range of RWH configurations to be evaluated at a given site. In addition, a decision support tool (RainWET) was developed and tested which enabled the methods to be deployed in real world settings. The application of the RainWET software allowed a UK-wide, time series analysis of RWH configurations to be completed and the holistic benefits of a range of dual purpose RWH systems to be analysed and described. Evidence from the UK study suggests that a traditional RWH installation (3000l storage, 300l/day demand and 60m2 roof) installed at a house in a water scarce region (London, SAAR 597mm) was able to fully mitigate stormwater overflows over a 20 year analysis whilst providing a mean water saving of 31,255l/annum. An equivalent system located in the wettest region studied (Truro, SAAR 1099mm) saw mean reductions in the largest annual storm of 62% (range 35-86%) whilst satisfying a mean rainwater demand of 50,912l/annum. The study concluded that suitably designed dual purpose RWH systems offered better stormwater management benefits than those designed without a stormwater control device. In addition, the integration of smart RWH controls were shown to maximise stormwater control benefits with little or no reduction in a system’s ability to satisfy non-potable water demands.

In the last three decades many sophisticated tools have been developed that can accurately predict the dynamics of flooding. However, due to the paucity of adequate infrastructure, this technological advancement did not benefit ungauged flood-prone regions in the developing countries in a major way. The overall research theme of this dissertation is to explore the improvement in methodology that is essential for utilising recently developed flood prediction and management tools in the developing world, where ideal model inputs and validation datasets do not exist. This research addresses important issues related to undertaking inundation modelling at different scales, particularly in data-sparse environments. The results indicate that in order to predict dynamics of high magnitude stream flow in data-sparse regions, special attention is required on the choice of the model in relation to the available data and hydraulic characteristics of the event. Adaptations are necessary to create inputs for the models that have been primarily designed for areas with better availability of data. Freely available geospatial information of moderate resolution can often meet the minimum data requirements of hydrological and hydrodynamic models if they are supplemented carefully with limited surveyed/measured information. This thesis also explores the issue of flood mitigation through rainfall-runoff modelling. The purpose of this investigation is to assess the impact of land-use changes at the sub-catchment scale on the overall downstream flood risk. A key component of this study is also quantifying predictive uncertainty in hydrodynamic models based on the Generalised Likelihood Uncertainty Estimation (GLUE) framework. Detailed uncertainty assessment of the model outputs indicates that, in spite of using sparse inputs, the model outputs perform at reasonably low levels of uncertainty both spatially and temporally. These findings have the potential to encourage the flood managers and hydrologists in the developing world to use similar data sets for flood management.

Community participation in flood planning has recently emerged as a successful approach to addressing and restricting the traditionally structural methods of flood control. Flooding, the most costly natural hazard worldwide, causes economic damages in spite of flood control efforts throughout the 20th century. To control flooding while allowing development, localities have traditionally used structural controls, such as levees and floodwalls, to physically separate floods from people. In light of the continued failure, high costs, and environmental degradation associated with structural flood controls, localities are now increasingly focusing on non-structural flood mitigation methods to reduce flood risks and losses. Furthermore, communities throughout the country are incorporating innovative flood projects that balance structural and non-structural flood mitigation in an attempt to better address environmental concerns. This approach involves returning previously damaged rivers and floodplains to their natural state. This evolution from structural approaches to environmentally conscious flood planning is illustrated through a case study of Napa, California’s model flood plan. Through an analysis of the flood plan and interviews with government representatives and project engineers, this case study illustrates how localities can design and implement flood plans to provide for environmentally sustainable flood mitigation. Building on a model of best management practices which incorporates the “living river” concept in the Napa River Flood Protection Project, this report suggests how other communities with severe river flooding can develop similar sustainable flood plans. Napa’s flood project represents a paradigm shift in which local residents were the driving force behind designing an environmentally sustainable and locally supported flood plan that would be carried out by the U.S. Army Corps of Engineers. The key lessons learned from Napa’s flood project are that community involvement and consensus building among stakeholders are crucial to developing and implementing an environmentally sustainable flood management project.

This thesis is directed to preparing for and managing floods that overwhelm floodplain management measures already in place in South East Queensland’s extensively developed residential floodplains. Such floods would generally have a magnitude greater than the 100 year annual recurrence interval. The thesis examines the context and preventative measures that lead to the development of counter disaster plans, and thence to examining the factors that affect decision makers prior to, and at the onset of a flood emergency. The standard flood mitigation tools are prevention through behaviour modification, land use planning, physical mitigation measures (aimed at modifying floodwater behaviour), and emergency planning. These measures can overlap, and the thesis finds that to be fully effective, the measures must be developed through interaction with the community, and be accompanied by community education and awareness programs. A great deal of work undertaken in the last 10 to 15 years has defined parameters for the sustainable use of flood prone land and emergency planning. Numerical modelling of hydrologic and hydraulic processes has improved significantly, and physical mitigation measures are well known. Additionally, thought has been devoted to the adverse consequences of flooding.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environemnt
Science, Environment, Engineering and Technology
Full Text

This study aims at developing a model to estimate flood damage cost caused in Gonaives, Haiti by Hurricane Jeanne in 2004. In order to reach this goal, the influence of income, inundation duration and inundation depth, slope, population density and distance to major roads on the loss costs was investigated. Surveyed data were analyzed using Excel and ArcGIS 10 software. The ordinary least square and the geographically weighted regression analyses were used to predict flood damage costs. Then, the estimates were delineated using voronoi geostatistical map tool. As a result, the factors account for the costs as high as 83%. The flood damage cost in a household varies between 24,315 through 37,693 Haitian Gourdes (approximately 607.875 through 942.325 U.S. Dollars). Severe damages were spotted in the urban area and in the rural section of Bassin whereas very low and low losses are essentially found in Labranle. The urban area was more severely affected by comparison with the rural area. Damages in the urban area are estimated at 41,206,869.57USD against 698,222,174.10 17,455,554.35USD in the rural area. In the urban part, damages were more severe in Raboteau-Jubilée and in Downtown but Bigot-Parc Vincent had the highest overall damage cost estimated at 9,729,368.95 USD. The lowest cost 7,602,040.42USD was recorded in Raboteau. Approximately, 39.38% of the rural area underwent very low to moderate damages. Bassin was the most severely struck by the 2004 floods, but Bayonnais turned out to have the highest loss cost: 4,988,487.66 USD. Bassin along with Labranle had the least damage cost, 2,956,131.11 and 2,268,321.41 USD respectively. Based on the findings, we recommended the implementation and diversification of income-generating activities, the maintenance and improvement of drains, sewers and gullies cleaning and the establishment of conservation practices upstream of the watersheds. In addition, the model should be applied and validated using actual official records as reference data. Finally, the use of a calculation-based approach is suggested to determine flood damage costs in order to reduce subjectivity during surveys.

Although literature on flood risk and environmental justice investigates the link between race and ethnicity and vulnerability to floods, few studies examine the distribution of flood mitigation amenities. This study analyzes census tract proximity to flood mitigation projects (FMPs) completed between 2012 and 2016 in Harris County, Texas to determine if a) project location is biased towards economic growth and the urban core; b) areas most impacted by previous floods are prioritized for drainage assistance; and c) if low-income and Latinx populations are being neglected. A spatial error regression analysis indicates that FMPs are significantly proximate to the urban core, net of other factors. Results also indicate no significant relationship between census tract-level Latinx composition, income status, and proximity to FMPs. Finally, built environment characteristics and locations of previous flooding had no significant effect on where projects were placed.

South Louisiana regularly experiences effects from flooding. This study looks at what homeowners are doing to reduce their losses from floods through the practices of flood mitigation. I developed four hypotheses to predict homeowners' mitigation behavior. (1) Homeowners with a history of flooding are likely to mitigate more than those without previous flooding. (2) High-disposable-income homeowners are more likely to mitigate than lowdisposable- income homeowners. (3) The stronger the place attachment among homeowners, the higher the likelihood they will mitigate. (4) Homeowners who have experienced effective mitigation measures in the past are more likely to mitigate than those who have not. To test these hypotheses, a survey was administered in five different neighborhoods throughout Orleans and Jefferson parishes having high concentrations of repeatedly flooded homes. The findings suggest severity of past flooding, disposable savings, strong relationships with neighbors, and discussion of flooding with neighbors are the strongest predictors of flood mitigation.

Sustainable development of floodplains is closely linked to sustainable flood mitigation measures. Various sustainability assessment (SA) methods to evaluate the influence of policies, plans or projects aimed towards sustainable development have been emerging in recent years. However, most of them are at the national or regional level. Very few research studies have been carried out for sustainability assessment of flood mitigation projects. This study proposes a new innovative decision support framework for sustainability assessment (SA) of flood mitigation projects throughout the project life cycle, focusing on two main aspects: sustainable flood mitigation by the project, and enabling of sustainable development of the floodplain. This study has employed a review of the life cycle of flood mitigation projects, a review of sustainability assessment methodologies, consultations with experts and case studies involving two flood mitigation projects in Queensland, Australia. Conforming to the project life cycle, the decision support framework for sustainability assessment of flood mitigation projects is developed incorporating five stages: 1) contextualizing the project with regard to floodplain sustainability, 2) SA during planning and implementation for integrating sustainability issues in the project, 3) SA during a flood event to assess the sustainability performance of the project 4) SA at periodic intervals, and 5) SA at the stage of modification or changing to a new project. The framework has adopted a multi-criteria analysis (MCA) approach using sustainability criteria and indicators to determine the sustainability index for the project. The process of selecting indicators, defining the weightages and scores for indicators, and determining a sustainability index for various stages of the project has been described in this thesis. The application of the SA framework to the first two stages of the two case study flood levee projects demonstrates how the best suitable alternative levee option can be chosen in the planning stage by determining a sustainability index (SI) of the possible alternatives using a set of sustainability indicators. The study also shows achievement towards sustainability of the finally implemented project can be compared with the originally planned project using the SA framework. The application of the SA framework suggests the potential for better decision making for individual flood mitigation projects, taking into account the sustainable outcomes of the project as well as linking these to sustainable regional development. The outcome of this study will enhance decision making for sustainability of flood mitigation projects. Adapting the framework to projects in other development sectors is also envisaged.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text

In order to reduce flooding, communities often try to control runoff with a storm sewer network, detention basins, low impact developments, and upstream storage to reduce stream overflow. Numerical models can help predict the effect these strategies will have before expensive construction projects are underway. A coupled 1D/2D hydraulic model using XPSWMM was created for the town of Kalona, IA, to test different strategies for flood reduction. XPSWMM utilizes one dimensional and two dimensional St. Venant equations to model flow in streams and pipes, or overland flow on the surface, respectively. The town of Kalona, upstream highlands, and the downstream floodplains were modeled utilizing a 4 meter cell-size unstructured grid. The model was neither calibrated nor validated, but its performance was comparable to a previously built MIKE 11/21 model of the same area when given the same inputs. The city drains into Salvesen Creek, the Central Drainage Ditch, and the East Drainage Ditch, with Salvesen Creek having the largest drainage area. 14 agricultural detention ponds upstream of the town were modeled to determine their effectiveness in reducing stream overflow, while modifications to the storm sewer network and in situ detention provided relief from local runoff. The detention ponds and modifications were modeled both separately and together and compared to a base model using the 10 year, 25 year, 50 year, 100 year, and 500 year, 3 hour storms. The different methods were compared using three index points: City Hall, Pleasant View Circle, and in a softball practice area. The upstream agricultural detention ponds provided a peak reduction of 2%, 13%, and 9%, respectively, while the in situ modifications reduced flooding by 0%, 44%, and 18%, respectively, for the 10 year storm. The combined techniques reduced flooding by 2%, 44%, and 20%, respectively. During the 100 year storm, the detention ponds, modifications, and combined techniques reduced peak flood depths by 17%, 24%, and 14%; 2%, 3%, and 22%; and 17%, 55%, and 23%, respectively. This demonstrated that the in situ modifications were more effective during low flood events while ponds were more effective at high flood events. The combined approach was most effective when the two methods complemented each other. Future work might determine areas throughout the town where reduced flow and in situ modifications together would be most effective and design approaches to maximize flood reduction. Additional features to be modeled include pumps to increase capacity in the storm sewer network, levees, and supplementary drainage channels.

This thesis explores the reconciliation of economic development and flood risk mitigation on the Humber Estuary, England. As sea level-rise is increasing due to suspected anthropogenic climate change, the Environment Agency has taken a lead role in mitigating flood risk on the Humber estuary through the process of governance. However, in trying to balance sustainable economic development with flood risk mitigation, the Environment Agency has experienced considerable difficulty in engaging local and regional businesses within the governance process. Analysis has found that although the overall importance of managing flood risk for businesses is reported to be greater in the present and the future than in the past, it remains more important for businesses which have previous experience of flooding than those which do not. Knowledge does not appear to transfer easily between different flood events, with concerns about recent pluvial flooding not percolating into risk perceptions concerning flooding from sea water. More alarmingly, businesses which have received flood risk information from the Environment Agency were found to have lower perceptions of the importance of flood risk management that those who had not, indicating a mismatch between scientific and lay knowledges. Without an understanding of how businesses perceive flood risk and how this affects participation within a governance process, the full engagement of the private sector within flood risk mitigation governance remains unlikely, therefore jeopardising sustainable economic development objectives on the Humber.

For decades Louisiana, especially Jefferson and Orleans parishes, has been affected severely by floods. These two parishes have experienced fifteen significant flood events in twenty six years from 1978 to 2004, either due to tropical weather or strong rainfall events. Those floods have resulted in billions of dollars in damages. In 1996 the Congress authorized a large flood control project called Southeast Louisiana Urban Flood Control Project (SELA). SELA is a large scale project that once complete, will improve the channels and the pumping stations in Orleans, Jefferson, and St. Tammany parishes. FEMA has limited sources for non-structural mitigation projects. Hence it is crucial to select the right properties for mitigation. This study focuses on identifying and creating a priority list of the properties in Jefferson Parish which will not have 100-year flood protection after all SELA projects are in place. These properties will require alternative non-structural mitigation measures.

The old water system in Sala, formerly belonging to thesilver mine, is analysed with regard to dam safety focusing onthe hydrological aspects. The hydrological safety of the riskclass I dams in the area, built in the 16th century, is notconsidered adequate according to the Swedish guidelines fordesign flood determination. A review is made of internationalprinciples for design flood determination. The overview showsthat there is no common principle used internationally whendealing with design flood for dams. In some countries there isan ambition to implement risk assessment for evaluation ofhydrological safety. However, at present Australia is the onlycountry that has fully integrated risk assessment in theirdesign flood guidelines. A risk assessment of the water systemin Sala shows that neither increasing the spillway capacity norimplementing flood mitigation measures in the watershed haveany significant effect on dam safety in the area. Nothingindicates that watersheds with a high presence of mires, likein the Sala case, should be particularly well suited forimplementing flood mitigation in the watershed as a dam safetymeasure. In order to safely handle the design flood in Sala andavoid dam failure due to overtopping the flood needs to bediverted from the water system.

Key words:dam safety; design flood; flood mitigation;hydrological; risk assessment

This document presents a sketch of the engineering and legal considerations necessary to implement a distributed storage flood mitigation system in Iowa. This document first presents the results of a simulation done to assess the advantages of active storage reservoirs over passive reservoirs for flood mitigation. Next, this paper considers how forecasts improve the operation of a single reservoir in preventing floods. After demonstrating the effectiveness of accurate forecasts on a single active storage reservoir, this thesis moves on to a discussion of distributed storage with the idea that the advantages of active reservoirs with accurate forecasting could be applied to the distributed storage system. The analysis of distributed storage begins with a determination of suitable locations for reservoirs in the Clear Creek Watershed, near Coralville, Iowa, using two separate algorithms. The first algorithm selected the reservoirs based on the highest average reservoir depth, while the second located reservoirs based on maximizing the storage in two specific travel bands within the watershed. This paper also discusses the results of a land cover analysis on the reservoirs, determining that, based on the land cover inundated, several reservoirs would cause too much damage to be practical. The ultimate goal of a distributed storage system is to use the reservoirs to protect an urban area from significant flood damage. For this thesis, the Clear Creek data were extrapolated to the Cedar River basin with the intention to evaluate the feasibility and gain a rough approximation of the requirements for a distributed storage system to protect Cedar Rapids. Discussion then centered on an approximation of the distributed storage system that could have prevented the catastrophic Flood of 2008 in Cedar Rapids. There is significant potential for a distributed storage system to be a cost effective way of protecting Cedar Rapids from future flooding on the scale of the Flood of 2008. However, more analysis is needed to more accurately determine the costs and benefits of a distributed storage system in the Cedar River basin. This paper also recommends that a large scale distributed storage system should be controlled by an entity be created within the Iowa Department of Natural Resources. A smaller distributed storage system could be managed by a soil and water conservation subdistrict. Iowa allows for condemnation of the land needed for the gate structures and the flowage easements necessary to build and operate a distributed storage system. Finally, this paper discusses the environmental law concerns with a distributed storage system, particularly the Clean Water Act requirement for a National Pollutant Discharge Elimination System permit.

Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第17877号
工博第3786号
新制||工||1579(附属図書館)
30697
京都大学大学院工学研究科都市社会工学専攻
(主査)教授 角 哲也, 教授 牛島 省, 准教授 竹門 康弘, 准教授 Sameh Ahmed Kantoush
学位規則第4条第1項該当

The importance of hydraulic structures has become an essential mitigating mean for floodsthat occur more often due to climate change. Thus, the importance and safety of flooddischarge tunnels has promoted further studies and experiments on the topic to mitigatedamages, such as cavitation that arise because of high speed flows.After an experimental study on a physical model was carried out on the flood discharge tunnelin Zipingpu Water Conservancy project, a CFD model was designed and simulated in thecommercial software ANSYS Fluent. The simulations aimed to evaluate and examine the riskfor cavitation in the tunnel, examine the design problems of the structure and analyse theinstalled aerators for the mitigation of cavitation. Moreover, using CFD models as acomplementary form to physical models was analyzed.A three dimensional geometry of the discharge tunnel was built in ANSYS Spaceclaim and themesh conducted with ANSYS mesh generator. The known boundary condition such as thedesign flow conditions, velocity inlet, pressure inlets and pressure outlet were set. For themodel a multiphase VOF scheme with RANS approach, k-ϵ turbulence model and a standardwall function was set.The results from the initial simulations showed that the discharge tunnel was under cavitationrisk, since the recorded cavitation index in the tunnel was below 1.8. After having revised thelayout of the aerators in order to mitigate cavitation risk, the results from the simulations withadded aerators were sufficient to mitigate the risk as the cavitation index was still below 1.8.The results for the cavitation index remained unchanged even in the simulated models with adifferent solver setup that were used in the comparison with the experimental data in order tovalidate them.As a conclusion, it was recommended that the tunnel design has to be revised and improvedby adding more aerators and air vents to mitigate the cavitation risk. Furthermore, more studieson the discharge tunnel or similar tunnels with similar conditions should be carried out in orderto validate the results of this study and determine if numerical models are preferable to physicalmodels

Flood risk is one of the most important topics under study of international researches usually associated at climate changes and unrestrained urbanisation resulting in a strong instability of weather conditions requiring a better control and forecast of climate trends and land use. A glance on current disasters around the world shows the relevance of flood risk and a continuous adjournment guarantees the awareness of the population about the dangerousness of flood effects. The analysis of potential floods shows several and different types of flood that could be grouped mainly in flash flood, fluvial flooding, coastal flooding and urban flooding. The most part of damages caused by these floods are linked with gaps on urban regulations that allow the realisation of built-up areas on unstable land as reclaimed lagoon, banks river area that create river path diversions, on coastal area as dunes or close to beaches, or even along river paths used to discharge volume of dams when the water level is close to the acceptable maximum level. Even though the improvement on technology, the impossibility to predict accurately weather conditions and the consequent uncertainty are worsening the situation of areas usually under flood risk. The deepened analysis conducted on flood event underlines the necessity to enhance the management of the flood risk forecasting the disasters and modelling potential scenarios with adequate hydrologic and hydraulic models in order to ensure right depicting of flood process development. The modelling of results as flow rate, water depth and flow velocity is fundamental to get hazard and risk flood maps that act as a springboard on a success predisposition of flood risk management plans. In the flood risk management plans, the identification of flood hazard and flood risk maps are used to define mitigation measures, usually divided in two main groups: structural and no-structural measures. The choice on the activation of structural and no-structural mitigation measures is mainly based on financial availability, time-step in measure realization, stakeholders preferences and government authority decisions. The considerable costs in realisation of mitigation measure is usually shore up by costs-benefits analysis methodologies representing a relevant support for decision makers. This research is focused on the definition and implementation of methodologies to evaluate potential flood damage of a baseline scenario and to support definition of mitigation measure scenarios. The work aims to identify the magnitude of the flood in terms of potential damages assessed considering the two main categorises of tangible and intangible damages. The flood damage evaluation is, herein, conducted with methodologies for an economic appreciation of the damage and implementation of models able to evaluate the potential number of fatalities and injuries due to flood meant as intangible damages reducible with efficient warning and evacuation issuances of flood emergency plans. These methodologies include different fields of research as hydrologic, hydraulic, agrarian, social, geological and political subjected at relevant uncertainties data included on the study.Finally, the damage reduction could be obtained implementing no-structural mitigation measures as the predisposition of flood management plans that include rules and tasks proper of flood emergency plans. Recent floods reveal that a correct preparedness of population and authorities on flood emergency reduce significantly damages and in particular victims and wounded. In fact, the second aim of in the project study the civil protection actions identified as crucial in the emergency management to prevent damages so much to require the identification of proper warning and evacuation time issuance, how they should be disseminated by the civil protection and local authorities after an accurate monitoring of climate conditions and management of people moves towards safe haven.

The management of fluvial flood risk in the UK is undergoing a paradigm shift, with a change in emphasis from structural defences to working with natural processes where possible. Natural Flood Management has been advocated by several interest groups as a potential option for providing a low cost, sustainable solution to catchment flooding. An integrated monitoring, field experimentation and modelling campaign has been undertaken to assess the potential of Natural Flood Management (NFM) to reduce flood risk in the rural Belford Burn catchment, Northumberland (5.7km2). The village of Belford failed to satisfy a risk-based cost-benefit criterion for structural defences, despite a number of floods occurring in recent years. The alternative low cost NFM mitigation approach taken in Belford involves the use of soft-engineered Runoff Attenuation Features (RAFs) that intercept or modify hydrological flow pathways. Within the Belford catchment 35 RAFs have been installed to date, including interception bunds, permeable timber barriers, large woody debris and offline storage ponds. The performance of a number of RAFs has been rigorously assessed using a combination of analyses of in situ observed data and modelling techniques. An innovative ‘Pond’ Model has been developed, which uses in situ observational data and physically-based methods, for evaluating the operational performance of the RAFs and assessing their impact on a number of historical flood events and design storms. In addition, the physical functioning and methodological approach of the Pond Model has been evaluated against a peer-reviewed hydraulic model. Also a hydrological modelling package was modified to also demonstrate the impact of RAF attenuation at the catchment scale, with the aim of creating a methodology for transferring the knowledge gained at Belford to other small catchments. This research has quantified the impacts of individual RAFs in the Belford catchment. From analyses of historical events, the Pond Model reveals that a network of attenuating features has the potential to significantly reduce peak flow (by up to 30%). However, for larger return interval design storms (for example 1:100 year return interval 24 hour duration) it is demonstrated that a certain/threshold of RAF attenuation features are required before the aggregate effects cause reduction in peak flow. The potential transferability of the approach and the methods used could have benefits for other similar small catchments (<10km2). An assessment of cost effectiveness is made that includes the comparison between the original iv cost of the proposed Belford flood alleviation scheme using a traditional structural methods and the RAF based scheme.

This research examines the importance of environmental factors in the choice, promotion and implementation of flood defence schemes in England and Wales. It focuses on the attitudes of National Rivers Authority (NRA) engineers and floodplain residents to low-frequency flood events and investigates the role of NRA engineers in influencing, the choices of floodplain residents. The theoretical focus includes an examination of the appropriateness of the dominant (North American) hazards research paradigm as an explanatory model in the British context and the development of a conceptual model applicable to this socio-political and cultural milieu. The research extends existing, primarily quantitative, research designs to include more qualitative approaches which provide descriptive richness and context beyond that afforded by quantitative data alone. The quantitative and qualitative studies of floodplain residents show environmental factors to be an important influence on their attitudes to proposals for flood hazard mitigation and to existing flood defence schemes. This is conceptualised as a 'risk-environment trade-off. The case studies of floodplain residents further identify an unmet information need concerning both flood risk and flood defence. The qualitative study of NRA engineers highlights the differences in perception and attitude between engineers and residents to flood risk, flood defence, public consultation and environmental factors. It underlines the complexity of the interactions which occur between individual, institutional and societal levels. The research concludes that the dominant paradigm model is inappropriately focused at the individual level and does not take sufficient account of institutional and structural influences. Furthermore, the concentration on choice rather than constraint ignores the social conflict and self-interest of actors in the decision-making environment. The research suggests that a systems approach is inadequate for dealing with the complexities of flood hazard mitigation.

This thesis evaluates the effectiveness of several flood mitigation strategies for reducing peak discharges in the Upper Cedar River Watershed located in northeast Iowa. Triggered by record flooding in June 2008, the Iowa Watersheds Project was formed to evaluate and construct projects for flood reduction. The Upper Cedar was selected as a pilot watershed and a hydrologic assessment was performed to better understand its flood hydrology. Evaluation of different flood mitigation strategies was performed with HEC-HMS, a lumped parameter surface water model. The hydrologic model development is described and the model applications are analyzed. The HMS model was used in several ways to better understand the flood hydrology of the Upper Cedar River Watershed. First, the runoff potential of the basin was assessed to identify the primary runoff generation mechanisms. Areas with agricultural land use and moderately to poorly draining soils had the highest runoff potential. Following, the model was used to evaluate the impact of several flood mitigation strategies - increased infiltration through land use changes, increased infiltration through soil improvements, and added storage in the watershed to hold runoff temporarily and reduce downstream flood peaks - for different flood frequency events (the 10-, 25-, 50-, and 100-year, 24-hour design rain storms) and the June 2008 flood. Although each scenario is hypothetical and simplified, they do provide benchmarks for the types of reductions physically possible and the effectiveness of strategies relative to one another. In order to reduce the impacts of flooding in the Upper Cedar, a combination of projects that enhance infiltration and/or store excess runoff will be necessary.

This thesis examines the relationships between rising water levels, vulnerable land, and sedimentation within the Chesapeake Bay watershed. Climate induced sea level rise threatens low lying coastal land, especially in regions of continuing subsidence such as the Chesapeake Bay. Alterations to shorelines over time have impacted the ability of coastal landscapes to capture and build up sediment, exposing them to continual erosion. The low lying neighborhood of Belle View along the Potomac River is the focus of the investigation due to its vulnerability to flooding and its cultural and ecological connections to the adjacent landscapes of Dyke Marsh and the George Washington Memorial Parkway. Through careful placement of breakwater infrastructure, sediment will build over time as the water rises, mitigating the effects of coastal flooding in this region. Alterations to the landscapes of the marsh and parkway allow for their cultural and recreational values to be strengthened over time as the landscape adjusts to the rising sea level.
Master of Landscape Architecture
Climate change, or the belief that human activity is altering the earth's climate, is projected to increase the occurrence of flood events due to water levels rising over time from glaciers melting. Previously, shorelines have been hardened with levee or seawall infrastructure to creates a barrier between the water and developed land. Hardened shorelines may increase water velocity and reflect wave energy in riverine landscapes, consequentially disturbing natural shorelines. This disturbance leads to the gradual loss of sediment over time and therefore a loss of ground elevation. When landscapes lose elevation, they become more vulnerable to rising water levels and flooding. This relationships between shoreline types, sedimentation, rising water, and vulnerability inspired me to discover and design a threatened landscape that would capture sediment within the river's water column to build elevation over time and protect the adjacent development from rising water. The area encompassing the low lying neighborhood of Belle View, Dyke Marsh, and the George Washington Memorial Parkway along the Potomac River is the focus of the investigation due to its vulnerability to flooding. With a careful understanding of sediment capture infrastructure dynamics, the design introduces breakwaters on the site to allow sediment to build over time as the water rises. This research and design thesis demonstrates a strategy to create landscapes that will evolve over time to mitigate future flooding events and create more resilient landscapes.

京都大学
0048
新制・課程博士
博士(地球環境学)
甲第22618号
地環博第197号
新制||地環||38(附属図書館)
京都大学大学院地球環境学舎地球環境学専攻
(主査)教授 柴田 昌三, 准教授 田中 周平, 准教授 深町 加津枝
学位規則第4条第1項該当
Doctor of Global Environmental Studies
Kyoto University
DGAM

This research explores perceptions of community flood resilience among adults from isolated settlements in Bangladesh’s Haor region from a perspective of change in the surrounding environment, with structural mitigation measures as outcomes of development planning activities. This research explains perceived resilience as the freedom of choice. This is achieved through eliminating all factors of vulnerability. Through discovering the reason for communities' dependency on external supports, this research proves the necessity of practicing community participation at a meaningful level and prioritizing community concerns and demands in the planning process.

Throughout history floods have been part of the human experience. They are recurring phenomena that form a necessary and enduring feature of all river basin and lowland coastal systems. In an average year, they benefit millions of people who depend on them. In the more developed countries, major floods can be the largest cause of economic losses from natural disasters, and are also a major cause of disaster-related deaths in the less developed countries. Flood disaster mitigation research was conducted to determine how remotely sensed data can effectively be used to produce accurate flood plain maps (FPMs), and to identify/quantify the sources of error associated with such data. Differences were analyzed between flood maps produced by an automated remote sensing analysis tailored to the available satellite remote sensing datasets (rFPM), the 100-year flooded areas "predicted" by the Flood Insurance Rate Maps, and FPMs based on DEM and hydrological data (aFPM). Landuse/landcover was also examined to determine its influence on rFPM errors. These errors were identified and the results were integrated in a GIS to minimize landuse / landcover effects. Two substantial flood events were analyzed. These events were selected because of their similar characteristics (i.e., the existence of FIRM or Q3 data; flood data which included flood peaks, rating curves, and flood profiles; and DEM and remote sensing imagery.) Automatic feature extraction was determined to be an important component for successful flood analysis. A process network, in conjunction with domain specific information, was used to map raw remotely sensed data onto a representation that is more compatible with a GIS data model. From a practical point of view, rFPM provides a way to automatically match existing data models to the type of remote sensing data available for each event under investigation. Overall, results showed how remote sensing could contribute to the complex problem of flood management by providing an efficient way to revise the National Flood Insurance Program maps.

In 2008 flooding occurred over a majority of Iowa, damaging homes, displacing residents, and taking lives. In the wake of this event, the Iowa Flood Center (IFC) was charged with the investigation of distributed flood mitigation strategies to reduce the frequency and magnitude of peak flows in Iowa. This dissertation is part of the several studies developed by the IFC and focused on the application of a coupled physics based modeling platform, to quantify the coupled benefits of distributed flood mitigation strategies on the reduction of peak flows in an agricultural watershed. Additional investigation into tile drainage and terraces, illustrated the hydrologic impact of each commonly applied agricultural practice. The effect of each practice was represented in numerical simulations through a parameter adjustment. Systems were analyzed at the field scale, to estimate representative parameters, and applied at the watershed scale. The impact of distributed flood mitigation wetlands reduced peak flows by 4 % to 17 % at the outlet of a 45 km2 watershed. Variability in reduction was a product of antecedent soil moisture, 24-hour design storm total depth, and initial structural storage capacity. The highest peak flow reductions occurred in scenarios with dry soil, empty project storage, and low rainfall depths. Peak flow reductions were estimated to dissipate beyond a total drainage area of 200 km2, approximately 2 km downstream of the small watershed outlet. A numerical tracer analysis identified the contribution of tile drainage to stream flow (QT/Q) which varied between 6 % and 71 % through an annual cycle. QT/Q responded directly to meteorological forcing. Precipitation driven events produced a strong positive logarithmic correlation between QT/Q and drainage area. The addition of precipitation into the system saturated near surface soils, increased lateral soil water movement, and reduced the contribution of instream tile flow. A negative logarithmic trend in QT/Q to drainage area persisted in non-event durations. Simulated gradient terraces reduced and delayed peak flows in subcatchments of less than 3 km2 of drainage area. The hydrographs were shifted responding to rainfall later than non-terraced scenarios, while retaining the total volumetric outflow over longer time periods. The effects of dense terrace systems quickly dissipated, and found to be inconsequential at a drainage area of 45 km2. Beyond the analysis of individual agricultural features, this work assembled a framework to analyze the feature at the field scale for implementation at the watershed scale. It showed large scale simulations reproduce field scale results well. The product of this work was, a systematic hydrologic characterization of distributed flood mitigation structures, pattern tile drainage, and terrace systems facilitating the simulation of each practices in a physically-based coupled surface-subsurface model.

The primary objective of this thesis is to develop hydrologic and hydraulic models for the Soap Creek Watershed, IA for the evaluation of alternative flood mitigation strategies and the analysis of the differences between hydrologic and hydraulic routing methods. In 2008, the state of Iowa suffered a disastrous flood that caused extensive damage to homes, agricultural lands, commercial property, and public infrastructures. To reduce the flood damage across Iowa, the U.S. Department of Housing and Urban Development (HUD) awarded funds to the Iowa Flood Center and IIHR-Hydroscience &Engineering at the University of Iowa to conduct the Iowa Watersheds Project. The Soap Creek Watershed was selected as one of the study areas because this region has suffered frequent severe floods over the past century and because local landowners have organized to construct over 130 flood detention ponds within it since 1985. As part of the Iowa Watersheds Project, we developed a hydrologic model using the U.S. Army Corps of Engineers’ (USACE) Hydrologic Center’s hydrologic Modeling System (HEC-HMS). We used the hydrologic model to evaluate the effectiveness of the existing flood mitigation structures with respect to discharge and to identify the high runoff potential areas. We also investigated the potential impact of two additional flood mitigation practices within the Soap Creek Watershed by utilizing the hydrologic model, which includes changing the land use and improving the soil quality. The HEC-HMS model simulated 24-hour design storms with different return periods, including 10, 25, 50, and 100 year. The results from modeling four design storms revealed that all three practices can reduce the peak discharge at different levels. The existing detention ponds were shown to reduce the peak discharge by 28% to 40% depending on the choice of observed locations and design storms. However, changing the land use can reduce the peak discharge by an average of only 1.0 %, whereas improving the soil quality can result in an average of 15 % reduction. Additionally, we designed a hydraulic model using the United States Army Corps of Engineers’ (USACE) Hydrologic Engineering Center’s River Analysis System (HEC- RAS) to perform a comparative evaluation of hydrologic and hydraulic routing methods. The hydrologic routing method employed in this study is the Muskingum Routing method. We compare the historical and design storms between HEC-HMS, HEC-RAS, and observed stage hydrographs and take the hydrograph timing, shape, and magnitude into account. Our results indicate that the hydraulic routing method simulates the hydrograph shape more effectively in this case.

This study aims to explore the possibility of environmental justice as social consensus and an institutional framework to reduce socioeconomic differences in natural disaster vulnerability through a case study of flood risk management in Johnson Creek, Portland, Oregon. First, by analyzing institutions, policies, and currently ongoing flood mitigation projects, this study investigates how federal and local governments are addressing and responding to current flood problems. Second, through flood expert surveys and GIS spatial analysis, this study examines various factors that contribute to communities' susceptibility to flood risks, and whether there exist spatial differences between physically and socioeconomically vulnerable communities within the Johnson Creek area. Lastly, this study conducted comparative analysis of perceptions using Q-methodology to explore the diverse range of meanings and understandings that flood experts and urban practitioners construct in relation to the dilemmas of environmental justice in flood mitigation practice. The findings of this study indicate that institutional blind spots and barriers in natural disaster mitigation policy and planning can be generated by flood experts' and urban practitioners' different understandings of vulnerability, different interpretations of human rights, and different perspectives on the extent of institutional responsibility to assist socioeconomically vulnerable populations.

Thesis: Ph. D. in Urban and Regional Planning, Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 264-280).
City leaders around the world are planning new infrastructure in response to the compound challenges of 1) flooding linked to climate change and 2) uneven urbanization. Advocates of contemporary flood mitigation efforts often frame their proposals as qualitatively different than the 'gray' levee and pump projects of previous generations. 20th century dry city infrastructural modernization projects promised to protect against flood hazards and enable urban growth, but they also had serious negative social and ecological consequences. New projects promise infrastructure that is 'green', flexible, and resilient. Building on changes in water management in the Netherlands, many recent projects around the world include a central role for designers and spatial planners. Though these new approaches have gained widespread favor, significant questions remain: Will these new flood mitigation efforts address the problems of previous generations or will they usher in more damaging mega-projects? How are the tools of design enabling and constraining transformative adaptation? To address these questions, this study analyzes the evolving politics of flood mitigation through a transnational case study of Dhaka and New Orleans, two levee-dependent cities that are considering sweeping changes to their flood mitigation strategies. The case studies use a range of data, including: archival research on flood mitigation and planning processes; field observations of built environment conditions; and interviews with residents, experts, and participants in recent planning processes. The study considers contemporary adaptation efforts in the context of historical flood mitigation and finds that, while emerging practices hold promise, there is reason for caution. By the end of the 20th century, both Dhaka and New Orleans had substantially similar systems of levees and pumps. The development of these dry city infrastructures was uneven, crisis-driven, and contested. Critics increasingly regarded levee-enabled growth as unwise and unjust. Though levee boosters promised that dry city infrastructures would bring modernization and orderly growth, once in place, each city's levees became embedded in broader socio-technical networks, or levee complexes, whose particular place-specific dynamics have created distinct patterns of uneven urbanization and vulnerability. The cases of Dhaka and New Orleans suggest that contemporary projects may not deliver their promised new paradigm of flood mitigation because: existing levee complexes are highly resistant to change; path-dependent dynamics bias planning towards 'big engineering'; and even those proposals that depart from previous practices are constrained by the entrenched material interests and epistemologies that have created the unwise and unjust patterns of the past. While the inclusion of designers offers the potential for improvements in urban flood mitigation projects, there are also serious challenges. When designers are not able or willing to grapple with the place-specific political contestations that come with major planning and infrastructure interventions, their tools can be used to depoliticize these processes, ignoring, obscuring, or rushing past the distributional impacts of flood and climate adaptation.
by Zachary Lamb.
Ph. D. in Urban and Regional Planning

The interactions between rivers, surrounding hydrogeological features, and hydraulic structures such as bridges are not well-established or understood at the network scale, especially under transient conditions. The cascading hydraulic effects of local perturbations up- and downstream of the site of perturbation may have significant, unexpected, and far-reaching consequences, and therefore often cause concern among stakeholders. The up- and downstream hydraulic impacts of a single structural modification may extend much farther than anticipated, especially in extreme events. This work presents a framework and methodology to perform an analysis of interdependent bridge-stream interactions along a river corridor. Such analysis may help prioritize limited resources available for bridge and river rehabilitations, allow better-informed cost/benefit analysis, facilitate holistic design of bridges, and address stakeholder concerns raised in response to planned bridge and infrastructure alterations. The stretch of the Otter Creek from Rutland to Middlebury, VT, is used as a test bed for this analysis. A two-dimensional hydraulic model is used to examine the effects individual structures have on the bridge-stream network, particularly during extreme flood events. Results show that, depending on their characteristics, bridges and roadways may either attenuate or amplify peak flood flows up- and downstream, or have little to no impact at all. Likewise, bridges may or may not be sensitive to any changes in discharge that result from perturbation of existing structures elsewhere within the network. Alterations to structures that induce substantial backwaters may result in the most dramatic impacts to the network, which can be either positive or negative. Structures that do not experience relief (e.g., roadway overtopping) may be most sensitive to network perturbations.

This Honours Industry Thesis identifies short- and long-term options on how to improve and restore the flow of Lake Carey, a salt lake in Western Australia, post-causeway construction. With major flood events occurring every 5-10 years and exploration Causeway Bravo built post the 2017 floods, options to mitigate the risk in case of flood events and to look at preventative management opportunities for construction of future causeways is critical. Obstruction of water flow, reduction in biodiversity and change in water quality are some of the major implications seen with causeways. This thesis adopts a systematic approach of data collection to establish the cause-and-effect relationship between policy, regulations, dewatering discharge in proximity of causeways and flood risks. This data is contributing in the first steps towards the under-researched topic of exploration causeways and flood-risk mitigation in the mining industry of Western Australia. The four objectives are as follows: • Analyse the risks involved with flood events and hypersaline dewatering discharge onto Lake Carey. • Collect data on Causeway Bravo and similar case studies and determine gaps in available data. • Identify and assess short- and long-term options for flood risk mitigation for Causeway Bravo. • Provide suggestions for the path forward. The adopted methodology commenced with a dewatering risk assessment to determine the original status of the lake and the characteristics of the dewatering discharge. Data collection on five case studies, including a high-level study on Causeway Bravo, has been conducted to identify the key characteristics per causeway, such as length, number, and type of culvert sections. The other case studies include: • Causeway D, Lake Carey, WA • Bindah Causeway, Lake Carey, WA • Main Causeway, Lake Lefroy, WA • Railroad Causeway in the Great Salt Lake, Utah, USA. Based on the collected data, four short-term options were identified and three long-term options. A multi-criteria assessment was then conducted with Gold Fields Australia which identified a hydrological assessment to identify lake flows, inflows and its bathymetry as the preferred short-term option and a main breach as the long-term option.

Heavy precipitation events are expected to increase in the future, due to climate change. This predicted change will increase the risk of flooding, especially in urban areas. To mitigate these challenges and support a sustainable urban development, Nature-based solutions (NBS) can be used as a flood risk reduction measure. The NBS wetlands and constructed wetlands, composed of ponds, canals and ditches, are commonly used solutions which are multifunctional and primarily provides flood regulatory services, water quality improvements and increased biodiversity. To reach the full potential of NBS, the location and design is crucial. At present planning practise, a user friendly and time efficient tool to investigate suitable locations within a catchment is missing, where the concept of connectivity has arisen as a useful approach. In this study, the NBS concept and the potential of wetlands for flood risk mitigation have been investigated. In addition, the connectivity of two study case catchments has been analysed by using the Connectivity Index (IC index) by Cavalli et al. (2013). The aim has been to evaluate whether the IC index can be used to find suitable locations for NBS. Further, the study seeks to investigate how the IC index can be integrated into NBS planning practice in order to create useful information for the decisionmaking process. To validate the IC index result, a comparison has been performed with earlier flood events, two hydrological models, Multi criteria decision analysis and spatiotemporal soil parameters. From the obtained result and analysis, preliminary solutions have been proposed for two case studies in Sweden and Portugal. The result shows that IC index is promising as an, early stage, first assessment tool in NBS planning practice which can be used in order to allocate areas suitable for NBS. To find the most beneficial location and the site-specific design, a deeper investigation of the site-specific conditions is required. Moreover, a successful implementation is dependent on a close collaboration between different stakeholders and expertise. Finally, this study shows that realizing the potential of NBS wetlands is essential to create sustainable urban development and liveable and attractive cities.

Shire of Murray has concerns regarding the negative impact that a 100 year flood could have on existing structures built before 1997. The increase cost in construction due to landfill has an adverse effect on development in Pinjarra. Feasibility of constructing a diversion channel at upstream of Murray River to attenuate the flood level from 1 in 100 year ARI to 1 in 50 year ARI, was investigated by Kiong (2003). The Murray River Water Surface Profile along three kilometres south of Greenlands Road was modelled. Flood damages on each flood occurrence were assessed and Average Annual Damage (AAD) was calculated. The AAD is used to estimate the monetary benefit against the construction cost of the diversion channel. Groundwater along Greenlands and Fauntleroy Drains was also modelled to determine the viable depth of the designed channel, as well as the analysis of backwater. The proposed channel is designed at different scenarios (invert level at breakout point, culvert or causeway design, and diversion channel variations). The benefit cost ratio of the proposed diversion channel is calculated. Other mitigation options are suggested including detention basins for structural measure, or building a new flood-proof township for non-structural measure.

Shire of Murray has concerns regarding the negative impact that a 100 year flood could have on existing structures built before 1997. The increase cost in construction due to landfill has an adverse effect on development in Pinjarra. Feasibility of constructing a diversion channel at upstream of Murray River to attenuate the flood level from 1 in 100 year ARI to 1 in 50 year ARI, was investigated by Kiong (2003). The Murray River Water Surface Profile along three kilometres south of Greenlands Road was modelled. Flood damages on each flood occurrence were assessed and Average Annual Damage (AAD) was calculated. The AAD is used to estimate the monetary benefit against the construction cost of the diversion channel. Groundwater along Greenlands and Fauntleroy Drains was also modelled to determine the viable depth of the designed channel, as well as the analysis of backwater. The proposed channel is designed at different scenarios (invert level at breakout point, culvert or causeway design, and diversion channel variations). The benefit cost ratio of the proposed diversion channel is calculated. Other mitigation options are suggested including detention basins for structural measure, or building a new flood-proof township for non-structural measure.

Os processos de cheias em bacias urbanas vêm sendo agravados devido a uma série de motivos associados à ocupação desordenada do solo urbano. As medidas de controle de enchentes podem ter sua eficiência analisada através da modelagem hidrológica matemática. É neste sentido que o presente trabalho analisa a influência da urbanização sobre os distúrbios no escoamento superficial, por meio de simulações de cenários urbanísticos propostos, com a finalidade de servir como ferramenta de planejamento urbano. Para isso, definiu-se como área de estudo, parte da bacia do Córrego do Gregório, São Carlos - SP. As principais informações da bacia a serem consideradas são: topografia, hidrografia, uso do solo urbano, expansão da área urbana, áreas de proteção ambiental e divisores de microbacias. O modelo hidrológico utilizado é o IPHS-1, do tipo concentrado. Para essa análise são propostos e simulados cenários urbanísticos, baseados na adoção de medidas de controle de inundações não-estruturais, referindo-se principalmente, à conservação de áreas verdes e disciplinamento do uso e ocupação do solo, verificando sua eficiência na redução do volume escoado e atenuação das vazões de pico.
The flooding processes in urban basins have become worse due to many reasons. All of them associated with the disorganized occupancy of the urban area land. The efficiency of flood mitigation measures can be analyzed by mathematical modeling. This study aims to be used as a tool for urban planning and it analyses the influence of the urbanization processes on surface runoff, using simulation of several urbanization scenarios. The case study was undertaken at the Gregório River Basin in São Carlos - SP. The main information considered was topography, hydrology, urban land use, urbanization, protected land and sub-basins. The software used was IPHS-1 which is a lumped hydrologic model. In this research many urbanization scenarios are proposed and simulated. These views are based in many nonstructural flood mitigation alternatives such as land cover conservation, use and occupancy of the land, in order to check their efficiency in reducing the total volume of surface runoff and the peak flow.

Terrace building have been expanded in the 19th century because of the increased demographic pressure and the need to crop additional areas at steeper slopes. Terraces are also important to regulate the hydrological behavior of the hillslope. Bench terraces, reducing the terrain slope and the length of the overland flow, quantitatively control the runoff flow velocity, facilitating the drainage and thus leading to a reduction of soil erosion. The study of the hydrologic-hydraulic function of terraced slopes is essential in order to evaluate their possible use to cooperate for flood-risk mitigation also preserving the landscape value. Few studies in literature are available on rainfall-runoff transformation and flood risk mitigation in terrace areas. Then, research results in this field are still scarce. The goal of this work is to improve knowledge on hydrological processes affecting a terraced slope and their effect on flood control. Specific researches objectives are: • Studing the the reduction of peak runoff at the toe of a hillslope and the delay in the passage of peak flow, which are provided by sequence of dry-stone walls under different space arrangements along the hillslope; • Understanding the rainfall-runoff separation mechanism and the superficial and subsurface flow propagation in case of terraced slopes. In order to reach the above objectives the hydrological response of a bench terrace was investigated by using a research approache based on modelling and experimental activities. In the first part of the thesis the The FLO-2D model is used to analyse the runoff propagation mechanism of a terraced slope (sequence of dry-stone walls) by varying number and spacing of terraces and assuming two hydrological soil setting scenarios in terms of antecedent moisture conditions within the Soil Conservation Service-Curve Number method. The model analysis shows that the majority of runoff modifications at the outlet of a terraced system result from topographical modifications rather than local variations of the infiltration capacity at the dry-stone wall zone. Repeated modelling applications show that, given a quite-typical scenario of a 20°-sloped hillslope and a reference intense rainstorm, the peak discharge reduction at the hillslope outlet depends on the percentage of the area managed with terraces. The reduction can be calculated with a logarithmic-type function (for example, an increase of terraced area from 10% to 30% might bring to runoff peak reduction of almost 45%). This information can help determine where terrace additions are more effective in terms of hydrological benefit. The second part of the thesis focus on an experimental/modelling research that aims to better focus the times of the hydrological response, which are determined by a hillslope plot bounded by a dry-stone wall, considering both the overland flow and the groundwater. A physical model, characterized by a quasi-real scale, has been built to reproduce the behavior of a 3%, 6% and 9% outward sloped terrace at bare and vegetated soil condition.The model consists of a steel metal box (1 m large, 3.3 m long, 0.8 m high) containing the hillslope terrain. The terrain is equipped with two piezometers, 9 TDR sensors measuring the volumetric water content, a surface spillway at the head releasing the steady discharge under test, two scales one at the wall base to measure the groundwater discharge and another at the top of the wall to measure the surface runoff. The experiments deal with different initial moisture condition (high and low degree of saturation), and discharges of 19.5, 12.0 and 5.0 l/min. Each experiment has been replicated, conducting a total number of 35 tests. The volumetric water content analysis produced by the 9 TDR sensors was able to provide a quite satisfactory representation of the soil moisture during the runs. Then, different lag times at the outlet since the inflow initiation were measured both for runoff and groundwater. Moreover, the time of depletion and the piezometer response have been monitored and analyzed, well corroborating the findings on the kinematics of the terrace plot. Finally, the computation of the specific Curve Number (Soil Conservation Service) of the physical model has revealed values rather large if compared with those reported in the literature. This phenomenon was likely caused by the high values of the inflow discharge, the limited cross-width of the model (1 m), the increasing compactness of the soil owing to the experiment repetition and the confined waterproof box). The experimental results indicate that terrace soil was highly heterogeneous, including discontinuities and piping systems that facilitated a rapid infiltration and the development of fast subsurface flow. The Groundwater in general is a small part of the total outflow but in case the presence of pipe is important it is coupled with impulsesive infiltration rates. A conceptual hydrological model was implemented and calibrated based on the experimental data. The model results fit well the measurements even if the groundwater component is not properly modelled. This is due to the activation of important piping systems during some of the tests; the physical proces that describ this located losses were not studied and integrated in the model. These pioneering experiments have produced some remarkable outcomes on the important role of lag-times (runoff and groundwater) and provided new knowledgement on the hydrological functioning of bench terraced systems for addressing more efficient management and maintenance issues of this important agricoltural structures.
I sistemi terrazzati si sono diffusi nel diciannovesimo secolo a seguito della crescente pressione demografica e della conseguente necessità di estendere le coltivazioni anche su terreni ad elevata pendenza. Oltre che dal punto di vista agrario tali sistemi sono importanti ai fini della regolazione della risposta idrogeologica di un versante. Infatti essi riducono la pendenza e la lunghezza dello scorrimento superficiale, controllando quindi quantitativamente la velocità del deflusso superficiale, facilitando il drenaggio e contribuendo in questo modo alla riduzione dei fenomeni erosivi. Lo studio della funzione idrologico-idraulica dei versanti terrazzati è essenziale per valutarne il possibile utilizzo come misure di mitigazione del rischio idraulico capaci anche di preservare il valore paesaggistico dei territori su cui essi insistono. In letteratura sono disponibili pochi studi inerenti la risposta idrologica di versanti terrazzati; l’avanzamento della ricerca in tale ambito è l’obiettivo principale di questo lavoro. In particolare vengono affrontate le seguenti tematiche: - la valutazione degli effetti di mitigazione della pericolosità idraulica (riduzione del picco di piena e suo ritardo temporale) a scala di versante indotti dalla presenza di sistemi terrazzati; - lo studio dei meccanismi di trasformazione afflussi-deflussi e dei processi di propagazione degli stessi in sistemi terrazzati; Al fine di raggiungere tali obiettivi è stato implementato un approccio integrato basato su attività sperimentali e modellistiche. Nella prima parte del lavoro è stato utilizzato il modello idraulico FLO-2D per analizzare i processi di propagazione in atto in un versante terrazzato (composto da una sequenza di muri a secco) al variare del numero e della disposizione spaziale dei terrazzi e assumendo due diversi scenari di saturazione del suolo rappresentati da diversi valori di umidità iniziale antecedente l'evento, come previsto dal metodo Soil Conservation Service - Curve Number. L'analisi modellistica mostra che la riduzione del deflusso alla base del sistema terrazzato dipende maggiormente dalle modifiche topografiche piuttosto che dalle variazioni della capacità di infiltrazione del suolo adiacente il muro. Le simulazioni eseguite su di un versante con una pendenza di 20° e alimentato da un evento di precipitazione intensa, mostrano che il picco di piena alla sezione di chiusura si riduce in funzione della percentuale di area terrazzata. Tale riduzione può essere valutata attraverso una specifica funzione logaritmica (per esempio, al crescere dell'area terrazzata da 10% a 30% la riduzione del picco di piena può essere quasi del 45%). Questa informazione può aiutare a individuare il corretto inserimento dei terrazzi per una maggiore efficace in termini di benefici idrologici. La seconda parte del lavoro riguarda lo studio della risposta idrologica di un’unità terrazzata con un muro a secco attraverso attività sperimentali e modellistiche. In particolare è stato costruito un modello fisico a scala reale per riprodurre il comportamento di un terrazzo al variare della sua pendenza (3%, 6% e 9%) e del tipo di copertura del suolo (suolo nodo o inerbito). Il modello consiste in un box metallico (1 metro di larghezza, 3.3 metri di lunghezza e 0.8 m di altezza) che contiene al suo interno un terrazzo composto da un versante delimitato a valle da un muro a secco. Tale versante è stato strumentato con 9 sensori TDR per la misura del contenuto di umidità del suolo, uno sfioratore delle portate liquidi in ingresso al versante a monte dello stesso, due bilance per la misura del deflusso, una posizionata alla base del muro per la misura del deflusso sotterraneo e una in corrispondenza della parte superiore del muro per la misura del deflusso superficiale. Gli esperimenti sono stati caratterizzati da differenti condizioni di umidità iniziale (ad alto e basso grado di saturazione) e da portate liquide in ingresso costanti e pari a 19.5, 12 e 5 l/minuto. Ogni esperimento è stato replicato per un totale di 35 esperimenti eseguiti. L'esame delle misure dei 9 sensori TDR ha fornito una soddisfacente rappresentazione dell'andamento dell'umidità globale del suolo nel corso di ogni esperimento. Sono stati poi misurati diversi tempi caratteristici della risposta idrologica alla sezione di chiusura sia per il deflusso superficiale che per il deflusso sotterraneo. I risultati ottenuti aiutano a comprendere la cinematica dei processi idrologici che caratterizzano l’unità terrazzata. E’ stato calcolato uno specifico Curve Number (Soil Conservation Service) associato all’unità terrazzata che assume valori piuttosto alti se comparati a quelli riportati in letteratura. Questo comportamento è probabilmente legato alle alte portate in ingresso, alla limitata sezione idraulica (1m), alla crescente compattazione del suolo causata dal susseguirsi delle prove e al fatto che il terrazzo è confinato all'interno di una struttura metallica impermeabile. Un innovativo modello idrologico è stato implementato e calibrato sui dati sperimentali. I risultati modellistici riproducono in modo soddisfacente le misure soprattutto per quanto riguarda il deflusso superficiale che è la componente prevalente di deflusso. In generale il deflusso sotterraneo non risulta invece essere propriamente simulato in quanto il modello non tiene conto di particolari fenomeni di infiltrazione impulsiva presenti in alcune prove. Infatti, i risultati sperimentali indicano che il suolo all'interno del terrazzo è altamente eterogeneo, con la presenza di discontinuità e sistemi di canali sotterranei che facilitano una rapida infiltrazione e lo sviluppo di deflusso sub-superficiale impulsivo che va a sommarsi al deflusso profondo (generalmente di modesta entità) alimentato dall’infiltrazione connessa agli strati superficiali del suolo. La sperimentazione effettuata risulta innovativa e fornisce nuove conoscenze sulla funzione idrologica-idraulica di un sistema terrazzato che possono servire per indirizzare in modo più efficiente la gestione e la manutenzione di queste importanti sistemazioni agrarie.

Inondations qui se produisent dans les zones urbaines sont régies par une fréquence accrue. Structures de protection contre les inondations existantes démontrent ses inconvénients. Une des solutions est émouvant de culture du risque et de trouver l'équilibre entre la forme de l'utilisation des terres et de l'urbanisation grâce à des stratégies d'adaptation, d'atténuation, de prévention et intervention et de rétablissement. La nouvelle approche globale est basée sur le concept de résilience donner une nouvelle place pour le développement et la mise en œuvre de nouvelles approches en vertu de gestion des risques d'inondation (FRM) cadres existants. Ajout de résilience à la gestion des risques d'inondation est une première étape. Grâce à une gestion des risques d'inondation opérationnelle a pour la résilience des prestations. L'indice résilience Flood (FRI) est développé dans cette thèse est une approche unique pour l'évaluation de la résistance aux inondations dans les systèmes urbains avec la priorité principale de la structure du système lorsque l'évaluation se fait sur les micro et méso échelle et sur la dimension du système lorsque la résistance aux inondations est évaluée sur macro échelle. La réflexion est mise sur le développement de la méthode par l'évaluation de la gestion des risques d'inondation existants (FRM) cadres. Grâce à l'évaluation, il est possible de constater le niveau d'intégration et de mise en œuvre de l'élément essentiel du risque d'inondation. La méthode développée pour l'évaluation de la résistance aux inondations est potentiellement applicable à tout système urbain à une échelle géographique
Floods that happen in urban areas are governed by increased frequency. Existing flood defence structures demonstrate its downsides. One of the solutions is moving to risk culture and finding the balance between the shape of land use and urbanization through adaptation, mitigation, prevention, and response and recovery strategies. The new holistic approach is based on resilience concept give a place for new development and implementation of new approaches under existing flood risk management (FRM) frameworks. Adding resilience to flood risk management is a first step. The Flood Resilience Index (FRI) is developed in this thesis is a unique approach for evaluation of flood resilience in urban systems with the main priority on system structure when evaluation is done on micro and meso scale and on system dimension when flood resilience is evaluated on macro scale. The main reflection is on the development of method by evaluation of existing flood risk management (FRM) frameworks. Through evaluation, there is a possibility to notice the level of integration and implementation of crucial element of flood risk. The developed method for evaluation of flood resilience is potentially applicable to any urban system of any geographic scale. Connections and dependences between main city elements and natural hazards (in this case urban flooding process) are defined. With its implementation, social, economical, political and cultural relations between cities will be more visible and better established and flood risk management well implemented