Academic literature on the topic 'Rill erosion'

The present paper is based on several field investigations (monitoring soil and rill erosion by aerial photography, rainfall simulations with portable rainfall simulators, and manmade rill flooding) in southern Spain. Experiments lead now to a closer understanding of the dynamics and power of different soil erosion processes in a gully catchment area. The test site Freila (Andalusia, Spain) covers an area of 10.01 ha with a rill density of 169 m ha−1, corresponding to a total rill length of 1694 m. Assuming an average rill width of 0.15 m, the total rill surface can be calculated at 250 m2 (0.025 ha). Given that, the surface covered by rills makes up only 0.25% of the total test site. Since the rill network drains 1.98 ha, 20% of the total runoff comes from rills. The rills’ sediment erosion was measured and the total soil loss was then calculated for detachment rates between 1685 g m−2 and 3018 g m−2. The interrill areas (99.75% of the test site) show values between 29 and 143 g m−2. This suggests an important role of rill erosion concerning runoff and soil detachment.

Abstract Few studies focus on the quantitative impact of upslope inflow rate and slope gradient on rill development and erosion processes. Field plot experiments under varying inflow rates (6–36 L min−1m−1) and slope gradients (26, 42 and 57%) were conducted to address this issue. The results showed soil loss rates significantly demonstrated temporal variability in relevance to the rill developing process. Rill erosion and its contribution to soil loss increased with increasing inflow rates and slope gradients by power functions. There was a threshold inflow discharge (12–24 L min−1m−1), under which, rill erosion became the dominant erosion pattern. At the initial stage, downcutting of rill bottom and headward erosion were obvious, whereas rill broadening was significant at the actively rill developing period. Rill density increased with slope gradient increasing from 26% to 42%, and then decreased. For the 57% slope under high inflow rates (24–36 L min−1m−1), gravity caused an increase in the collapse of rills. Mean rill width increased with increasing inflow rates but decreased as slope gradients increased, while mean rill depth increased with increasing inflow rates and slope gradients. Stream power and rill flow velocity were the best hydrodynamic parameter to simulate rill erosion and rill morphology, respectively.

ABSTRACT Soil erosion is a major environmental problem in many parts of the world and represents a serious problem for sustainable agriculture and the environment, with direct and indirect impacts on soil quality and fertility. This study aimed to use the Water Erosion Prediction Project (WEPP) model to estimate rill erosion and determine soil physical and hydraulic properties, which are essential to investigate its performance. To this end, an experiment was carried out in the Exu Creek watershed, in Serra Talhada, semi -arid region of Pernambuco State (Brazil), under increasing flow rates: T1: 5.87 L min-1; T2: 12.10 L min-1; T3: 20.33 L min1; and T4: 27.57 L min-1. Liquid and solid discharges were sampled for determination and characterization of hydraulic parameters in preformed rill flows. Reynolds numbers between 2,019 and 6,929 and Froude numbers below 1 found in this study attest to occurrence of erosive rills. Soil losses due to rill erosion increased as flow rates increased. Rill erodibility was 0.0011 kg N-1 s-1, and critical shear stress (tc) was 1.91 Pa, collapsing rill sidewalls and increasing local uplift, wet perimeter, and rill hydraulic radius.

Rill erosion is an important kind of slope erosion and the main source of sediment. Through simulated rainfall tests, the morphological characteristics of rill were quantified by stereophotogrammetry technology, and the relationship between rill development and sediment yield was studied. The results show that there was a positive correlation between sediment yield and slope and rainfall intensities. With the increase in rainfall duration, sediment yield first increased sharply and then decreased gradually after reaching the peak value, until it reached dynamic stability. With the increase in rainfall intensity and slope, the length, width, and number of rills increased significantly, with a maximum length of 2.58 m and a maximum width and depth of 9.7 and 2.2 cm. The rill density (RD) increased from 16.67% to 62.65%; rill fragmentation degree (RFD) increased from 16.67% to 100.00%; rill complexity (RC) increased from 10.62% to 30.84%, and rill width–depth ratio (RWDR) decreased from 15.82% to 56.28% with the increase in slope from 6° to 15° and rainfall intensity from 2.0 to 3.0 mm/min. There was a good nonlinear relationship between sediment yield and RC and RWDR (R2 = 0.89, NSE = 0.85, n = 10). This study could provide help for the quantification research of rill erosion mechanisms and provide reference for the measurement and scale transformations of soil erosion at different scales.

The presence of compacted layers in soils can induce subprocesses (e.g., discontinuity of water flow) and induces soil erosion and rill development. This study assesses how rill erosion in Oxisols is affected by a plow pan. The study shows that changes in hydraulic properties occur when the topsoil is eroded because the compacted layer lies close below the surface. The hydraulic properties that induce sediment transport and rill formation (i.e., hydraulic thresholds at which these processes occur) are not the same. Because of the resistance of the compacted layer, the hydraulic conditions leading to rill incision on the soil surface differed from the conditions inducing rill deepening. The Reynolds number was the best hydraulic predictor for both processes. The formed rills were shallow and could easily be removed by tillage between crops. However, during rill development, large amounts of soil and contaminants could also be transferred.

The main purpose of this article is to give a general idea of the scientific activity that was carried out starting from the 2000s on the basis of the data collected in the plots installed at the Sparacia experimental station for soil erosion measurement in Sicily, South Italy. The paper includes a presentation of the experimental site, a description of the methods and procedures for measuring soil erosion processes both available in the literature and applied at the Sparacia station (sediment sampling and water level reading in the storage tanks for total erosion measurements; profilometer, and Structure from Motion technique for rill erosion measurements), and the main results obtained in the monitoring period in the experimental site. The latter concern the effects of plot size and steepness on soil loss, the measurement variability, the frequency analysis of soil loss, the rill erosion characterization, and the comparison between rill and interrill erosion rates. Each of these topics is addressed with multi-temporal analyses performed with increasing size of the available database, which allowed to draw robust conclusions. Soil loss did not vary appreciably with plot length in contrast with the assumption made in the USLE/RUSLE. The variability of the measurements of soil loss, runoff volume, and sediment concentration at the event scale in replicated plots decreased as the mean measured value increased. The normalized event soil loss was distributed according to a two-component distribution. A power relationship between rill volumes and lengths was established. The measurements also confirmed the morphological similarity between the channels of the rills and ephemeral gullies described by a power dimensionless relationship. Rill erodibility of the sampled clay soil varied over time, maintaining relatively low values. Finally, rill erosion was dominant relative to interrill erosion, and a more efficient sediment transport system through the rill network occurred as plot steepness increased.

Water erosion is the main cause of soil degradation in agricultural areas. Rill erosion can contribute vastly to the overall erosion rate. It is therefore crucial to identify areas prone to rill erosion in order to protect soil quality. Research on rainfall-runoff and subsequent sediment transport processes is often based on observing these processes at several scales, followed by a mathematical description of the observations. This paper presents the use of a combination of data obtained by different approaches at multiple scales to validate the SMODERP2D episodic hydrological-erosion model. This model describes infiltration, surface retention, surface runoff, and rill flow processes. In the model, the surface runoff generation is based on a water balance equation and is described by two separate processes: (a) for sheet flow, the model uses the kinematic wave approximation, which has been parameterized for individual soil textural classes using laboratory rainfall simulations, and (b) for rill flow, the Manning formula is used. Rill flow occurs if the critical water level of sheet flow is exceeded. The concept of model validation presented here uses datasets at different scales to study the surface runoff and erosion processes on the Býkovice agricultural catchment. The first dataset consisted of runoff generated by simulated rainfall on plots with dimensions of 2 × 8 m. The second dataset consisted of the runoff response to natural rainfall events obtained from long-term monitoring of 50 m2 plots. These two datasets were used to validate and calibrate the sheet flow and infiltration parameters. The third dataset consisted of occurrence maps of rills formed during heavy rainfalls obtained using remote sensing methods on a field plot with an area of 36.6 ha. This last dataset was used to validate the threshold critical water level that is responsible in the model for rill flow initiation in the SMODERP2D model. The validation and the calibration of the surface runoff are performed well according to the Nash–Sutcliffe efficiency coefficient. The scale effect was evident in the 50 m2 plots where parameters lower than the mean best fit the measured data. At the field plot scale, pixels with measured rills covered 5% of the total area. The best model solution achieved a similar rill cover for a vegetated soil surface. The model tended to overestimate the occurrence of rills in the case of simulations with bare soil. Although rills occurred both in the model and in the monitored data in many model runs, a spatial mismatch was often observed. This mismatch was caused by flow routing algorithm displacement of the runoff path. The suitability of the validation and calibration process at various spatial scales has been demonstrated. In a future study, data will be obtained from various localities with various land uses and meteorological conditions to confirm the transferability of the procedure.

With the release of the Revised Universal Soil Loss Equation (RUSLE) there is potential to consider a range of responses of erosion to increasing slope length. This paper presents data to illustrate commonly observed effects of increasing overland flow on erosion processes and erosion rates, and considers the application of the data to specifying land management strategies and forms of vegetative cover most suited to particular soils. It also discusses a methodology for assessing relevant slope length factors for the RUSLE based on rill/interrill susceptibility. Three basic responses to slope length are noted: (i) little increase in erosion per unit area with increasing length, due to either the failure of rills to develop for the range of overland flows considered, or rill formation at very low hows with no further increase in erosion rates as flow rates increase; (ii) moderate increase in erosion per unit area with slope length associated with slight rill development; and (iii) large increases in erosion per unit area with slope length as rilling develops strongly. These responses have significance for the relative importance of surface and contact cover (and therefore, for the plant species grown and/or residue management strategy adopted), and for the use of contour banks to reduce slope length.

Soil properties are influenced by freeze-thaw, which in turn influences soil erosion. Despite this, only a few studies have investigated the impacts on soil hydrodynamic processes. The objective of this study was to evaluate the impact of soil freezing conditions on runoff, its energy consumption, and soil erosion. A total of 27 laboratory-concentrated meltwater flow experiments were performed to investigate the soil erosion rate, the runoff energy consumption, and the relationship between the soil erosion rate and runoff energy consumption by concentrated flow under combinations of three flow rates (1, 2, and 4 L/min) and three soil conditions (unfrozen, shallow-thawed, and frozen). The individual and combined effects of soil condition, flow rate, and runoff energy consumption on the soil erosion rate were analyzed. For the same flow rate, the shallow-thawed and frozen slope produced mean values of 3.08 and 4.53 times the average soil erosion rates compared to the unfrozen slope, respectively. The number of rills in the unfrozen soil slope were 4, 3, and 2 under the flow rate of 1, 2, and 4 L/min, respectively. The number of rills in the thawed-shallow and frozen soil slope were all 1 under the flow rate of 1, 2, and 4 L/min. The rill displayed disconnected distribution patterns on the unfrozen slope, but a connected rill occurred on the shallow-thawed and frozen slopes. The average rill width on unfrozen, thawed-shallow, and frozen soil slopes increased by 1.87 cm, 4.38 cm, and 1.68 cm as the flow rate increased from 1 L/min to 4 L/min. There was no significant difference in the rill length on the frozen slope under different flow rates (p > 0.05). The runoff energy consumption ranged from unfrozen > shallow-thawed > frozen slopes at the same flow rate. The soil erosion rate had a linear relationship with runoff energy consumption. The spatial distribution of the runoff energy implied that soil erosion was mainly sourced from the unfrozen down slope, shallow-thawed upper slope, and frozen full slope.

Interrill and rill erosion are commonly observed erosion processes to coexist on hillslope. Understanding of the interrill and rill erosion process is the key for the development of physically-based erosion prediction models. This paper reviewed the research progress of interrill and rill erosion, and the relationship between them. The shortages were also put forward. Finally, the trends for future development and questions are also discussed.

Accurate estimation of the shear stress of flowing water is important in modeling rill and interrill erosion. The shear stress of flow in rills helps determine detachment capacity and transport capacity of flow. This study investigated shear stress estimation in erosion modeling. Rill shear stress estimates based on sheet flow and on flow partitioned into rill and interrill areas for a uniform slope were compared. It was found that the sheet flow assumption underestimated actual shear stress in rills. Estimates of rill spacing and rill width affect shear stress in rills. It was found that increasing the distance between rills could increase predicted sediment loads while sediment loads reached a maximum then decreased for increased rill widths. Erodibililty parameters for an erosion model were found using optimization. Optimal values for rill erodibility parameters were found to be distorted when based on a model that estimated shear stress from sheet flow.

This research examines the use of remote sensing techniques to quantify rill erosion in two agricultural fields in the Lower Fraser Valley. Soil erosion during the winter is particularly problematic in some of the sloping soils developed from loess over glacio-marine parent materials. New techniques are needed to quantify rill erosion on a timely basis, and this research focuses on measuring the extent and rate of rill erosion from field and aerial photograph measurements. A model which used rill measurements as input, was used to determine the rill plan areas, rill volumes, and thus rill erosion rates in the test area. Using field rillometer measurements of rills as input into the model resulted in a soil loss estimate of 49m³ /ha/yr or 38.4 t/ha/yr for the test site. This soil loss estimate is deemed to be more reliable than erosion plot and Universal Soil Loss Equation estimates of soil loss for the test area. The rill volume and plan area of three main rills, using three different rill measurement methods for input into the model, were compared. Using field measuring tape measurements of rills as input into the model, resulted in a soil loss estimate which was 16 % greater than the estimate from rillometer measurements. Using photo rill width measurements and an estimation of rill depths and bottom widths from field data as model input, resulted in a soil loss estimate which was 22 % less than the estimate from rillometer measurements. Spectral reflection measurements made in rill, interrill and depositional areas were found to be significantly different, confirming that rill erosion could be assessed in a quantitative manner using digital image analysis techniques. The spectral separation was largely due to differences in organic matter, surface roughness and imaging geometry. The latter is of particular importance in creating darker shadowed rill sides opposite bright sun-facing rill sides within a single rill. A maximum likelihood classifier, used as part of the computer based image analysis, determined the rill plan area for a sample area to be 9 % less than the rill plan area obtained from the model using rillometer input. This indicates the potential of digital analysis to quickly determine the plan area of larger rills. Digital elevation and moisture content data confirmed that the topographic shape of the field is important in determining the spatial pattern of rill formation. The combination of such data with image analysis and geographic information systems (GIS) have great potential in the timely quantification of erosion in the future.<br>Land and Food Systems, Faculty of<br>Graduate

I processi erosivi costituiscono un rilevante problema ambientale con impatto anche di tipo socioeconomico. Infatti, questi processi determinando l’asportazione degli strati superficiali di suolo, causano la riduzione della fertilità e produttività del suolo, e hanno un considerevole impatto sulla biodiversità. La perdita di suolo dovuta all’erosione idrica è un fenomeno naturale ed inevitabile, che può divenire intollerabile in condizioni particolari che spesso dipendono da fattori antropici (Di Stefano e Ferro, 2016). I processi di erosione idrica sono generalmente caratterizzati dall’erosione interrill o rill. Nelle aree interrill, caratterizzate da correnti overland, il processo erosivo preponderante è dovuto all’impatto delle gocce di pioggia, e il sedimento viene trasportato dalla corrente da queste aree verso i rill. I rill, invece, sono solchi di modeste dimensioni planimetriche, poco profondi ed effimeri, che operano come principale sorgente di sedimento, in cui vengono trasportate le particelle provenienti delle aree interrill e quelle distaccate dalla superficie laterale del rill stesso (Di Stefano et al., 2013). L’erosione rill rappresenta la principale fonte di sedimento a scala di versante dato che più dell’80% delle particelle erose nei versanti è trasportato nei rill (Mutchler e Young, 1975). Lo studio dei processi fisici e dei meccanismi che determinano l’erosione idrica risulta necessario per meglio comprendere il fenomeno erosivo e per stimare i valori di perdita di suolo. L’erosione rill dipende strettamente dalle caratteristiche idrauliche della corrente che muove all’interno del rill (Foster et al., 1984), per cui al fine di studiare e modellare i processi erosivi, oltre alla portata Q, devono essere determinate altre caratteristiche idrauliche, come la larghezza w, il tirante idrico h, la velocità media della corrente V, e l’indice di scabrezza (Gilley et al., 1990). Nonostante le differenze tra i rill e i corsi d’acqua, uno degli approcci più comuni per la stima della velocità media della corrente nei rill è basato sull’utilizzo delle equazioni dell’idraulica classica, come quelle di Manning o di Chezy. Nella presente Tesi sono presentati i risultati di sperimentazioni condotte per la determinazione della legge di resistenza al moto nelle correnti rill. È stato, inoltre, analizzato il contributo alle resistenze totali della componente grain, dovuta alla dimensione caratteristica degli elementi che determinano la scabrezza, della morphological resistance, dovuta alle forme di fondo come gli step-pool, e della resistenza dovuta al trasporto solido. Una legge teorica di resistenza al moto è stata dedotta a partire dall’integrazione del profilo potenziale di velocità della corrente (Ferro, 1997, 2003), ottenuto applicando l’analisi dimensionale (Barenblatt, 1993; Ferro, 1997) e l’ipotesi di auto-similitudine incompleta (Ferro e Pecoraro, 2000; Di Stefano et al., 2017b; Ferro, 2017). I rill sono stati incisi manualmente su due parcelle, modellati con una corrente limpida e le prove sperimentali sono state condotte in tratti di rill al fine di misurare la velocità media della corrente, il tirante idrico, l’area delle sezioni trasversali, il contorno bagnato e la pendenza del tratto. Un metodo di rilievo di tipo image-based, che combina le tecniche Structure from Motion (SfM) e Multi-View Stereo (MVS), è stato applicato per realizzare il modello 3D dei rill. Sono stati utilizzati cinque differenti tipi di suolo, con pendenza variabile tra il 9 e il 26%, e sono state eseguite prove sia a fondo mobile che fisso. Le misure ottenute hanno consentito di sviluppare tre differenti analisi. Per la prima analisi sono state utilizzate 472 misure sperimentali, caratterizzate da differenti tessiture del suolo e pendenze della parcella, per calibrare e verificare l’equazione per la stima della funzione Γ del profilo di velocità e determinare, conseguentemente, la legge di resistenza al moto. Nella relazione proposta, la tessitura è rappresentata dal contenuto percentuale di argilla e limo. L’analisi ha mostrato che sia la frazione argillosa che quella limosa, rappresentative della distaccabilità e trasportabilità delle particelle di suolo, condizionano la velocità media della corrente rill. Infatti, l’indice di scabrezza aumenta all’aumentare della frazione limosa (elevata distaccabilità) e al diminuire della frazione argillosa (bassa trasportabilità). In altri termini, il risultato ottenuto dimostra che l’incremento di resistenza al moto dovuto al carico solido è influenzato sia dalla distaccabilità che dalla trasportabilità delle particelle di suolo. La seconda analisi, condotta utilizzando 199 misure sperimentali ottenute in presenza di step-pool nei rill, ha permesso di calibrare e verificare l’equazione per la stima della funzione Γ sia per rill a fondo mobile che per rill a fondo fisso. L’equazione calibrata per i rill a fondo mobile è risultata applicabile anche alle misure ottenute su fondo fisso perché l’effetto del trasporto solido sulle resistenze al moto può essere ritenuto trascurabile rispetto alle resistenze dovute alla morfologia a step-pool. La configurazione di rill con step-pool è risultata caratterizzata da valori dell’indice di resistenza di Darcy-Weisbach più elevati di quelli ottenuti per rill a fondo mobile senza forme di fondo. Lo scopo della terza ed ultima analisi è stato quello di valutare il contributo della resistenza al moto dovuta al trasporto solido rispetto alla resistenza totale utilizzando le misure effettuate su rill a fondo piano, sia mobile che fisso per due differenti database. Per le condizioni sperimentali esaminate questo tipo di resistenza è risultata spesso trascurabile. Per le tre analisi effettuate, l’approccio teorico è risultato applicabile in quanto sono stati ottenuti bassi valori degli errori nella stima dell’indice di resistenza di Darcy-Weisbach. In tutti i casi esaminati l’ipotesi del meccanismo “feedback” proposta da Govers (1992), per la quale la velocità media della corrente è indipendente dalla pendenza, è stata confermata. Per le prove effettuate su rill a fondo fisso questo risultato può essere spiegato da un effetto feedback “memorizzato”, determinato dalle prove a fondo mobile effettuate prima delle operazioni di irrigidimento dei solchi o dalla fase di modellamento. In conclusione, la stima della funzione Γ del profilo di velocità e la conseguente applicazione della legge teorica di resistenza al moto è risultata affidabile sia nel caso di rill a fondo piano (grain resistance), sia nel caso di rill con step-pool (morphological resistance). La suddetta equazione ha consentito anche di valutare l’effetto del trasporto solido sulla resistenza al moto della corrente rill.<br>Erosive processes are a relevant environmental problem of our society. In fact, these processes have many consequences reducing the soil fertility and productivity, worsening air and water quality and impacting the biodiversity reducing the variety of communities. Water erosion is one of the most determining phenomena regarding soil erosion and soil loss. Soil loss due to water erosion is a natural and inevitable phenomenon, but it can become intolerable in particular conditions often determined by anthropic factors (Di Stefano and Ferro, 2016). Water erosion processes are generally characterized as either interrill or rill erosion. On interrill areas, characterized by spread flow (overland flow), the main erosion process is due to raindrop impact, and the sediment is transported by flow from these areas to rills. Instead, rills are small, shallow, and ephemeral flow paths which work as sediment sources and are able to transport particles delivered from interrill areas and those detached by rill flow along the rill wetted perimeter (Di Stefano et al., 2013). Rill erosion is the main sediment source at hillslope scale and more than 80% of the eroded particles from hillslopes are transported in rills (Mutchler and Young, 1975). The study of the physical processes and mechanisms which determine water erosion becomes a fundamental tool to understand in a better way the problem, estimate the soil loss and try to manage it. The rill erosion strictly depends on hydraulic characteristics of the flow which moves within the rill (Foster et al., 1984) and for this reason to study and model rill erosion processes, in addition to flow discharge Q, other hydraulic characteristics, as width w, water depth h, mean flow velocity V, and roughness coefficient, must be defined (Gilley et al., 1990). One of the most common available approach to estimate the mean flow velocity in rills, notwithstanding the difference between them and rivers, is the use of classical hydraulic equations, such as Manning's and Chezy's equation. In this dissertation experimental investigations were carried out to determine the rill flow resistance law, analyzing the behavior and the contribution to the total resistance of the grain component, due to the characteristic dimension of the elements which determine bed roughness, morphological resistance, due to bed forms as step-pools, and the resistance related to sediment transport phenomena. A theoretical flow resistance law was deduced integrating a power flow velocity profile (Ferro, 1997, 2003), obtained applying the dimensional analysis (Barenblatt, 1993; Ferro, 1997) and the self-similarity hypothesis (Ferro and Pecoraro, 2000; Di Stefano et al., 2017b; Ferro, 2017). Rills were manually shaped on plots and deepened by a clear flow and experimental runs were carried out on rill reaches to measure mean flow velocity, water depth, cross-section area, wetted perimeter, and channel slope. An image-based technique, which couples Structure from Motion (SfM) and Multi-View Stereo (MVS), was applied for obtain the ground measurements by 3D models. The plots were filled with five different soil types, the plot slopes sp varied from 9 to 26%, and both mobile and fixed bed conditions were examined. Using the obtained measurements three analyses were developed. For the first investigation 472 experimental runs, characterized by different soil textures and slopes, were used to calibrate and test the equation to estimate the Γ function of the velocity profile and consequently obtain the flow resistance law. The different soil textures were represented by clay and silt percentage. The analysis demonstrated that clay and silt fractions of the investigated soils are sufficient for representing the effect of erosion and transport of soil particles on rill flow velocity. In fact, the friction factor increases when silt fraction increases (high detachability) and clay fraction decreases (low transportability). In other words, this result expresses that the increase of flow resistance due to sediment load is affected by both soil detachability and transportability. The second investigation, carried out using 199 experimental runs for which step-pools occurred, allowed to calibrate and test the equation to estimate the Γ function for both mobile and fixed bed rills characterized by the occurrence of the morphological resistance. The equation calibrated by mobile bed rills is applicable to the fixed bed condition and this result is explainable since the effect of sediment transport on the flow resistance law can be considered negligible respect to the form-induced flow resistance (spill resistance) due to the presence of step-pools structures. The analysis confirmed that the step-pool configuration is characterized by Darcy-Weisbach friction factor values higher than those obtained for rills with a flat bed. The aim of the third and last analysis was to evaluate the contribution of the resistance due to sediment transport on total one comparing the runs carried out on mobile and fixed bed rills for two different databases. For these experimental conditions this type of resistance resulted often negligible. The theoretical approach resulted successful and was characterized by low errors in the estimate of the Darcy-Weisbach friction factor for the three conducted analyses. In all cases the “feedback mechanism” hypothesis suggested by Govers (1992), for which the mean flow velocity is independent by the slope gradient, was confirmed. For fixed bed runs this result can be justified by a “frozen” feedback caused by mobile bed runs before fixing operations or by the shaping phase. In conclusion, the estimate of the Γ function of the velocity profile and the application of the theoretical flow resistance is successful and reliable for both grain and morphological resistance and is also useful to investigate sediment transport effects.

The Santa Rosa Creek watershed is one of the most pristine watersheds on California’s Central Coast. Preserving this watershed is of great interest because it provides rich soils for agriculture, vast rangelands for cattle, and flowing streams for federally threatened species such as steelhead trout. Soil erosion could impact these resources. Using prediction tools, it is possible to study the erosion that could be occurring in a watershed and identify locations which could contribute the highest amounts of sediment. The objectives of this study were to use RUSLE2 and Geographic Information Systems (GIS) to predict soil erosion rates for each soil map unit in every drainage of the upper Santa Rosa Creek watershed and to determine areas where soil erosion could surpass a soil development rates. Environmental and anthropogenic factors that influence soil erosion such as topography, climate, soil, geology, vegetation, and land use, were described for the entire watershed to provide supplementary data used in the RUSLE2 model and to explain erosion in highly erosive areas. Predicted soil erosion rates were studied to determine if correlations exist between other factors such as slope, existing erosion features, and vegetation. Predicted soil erosion rates calculated using RUSLE2 confirmed that the watershed is healthy and that 98 percent of the drainages are within sustainable soil erosion rates (five tons/acre/year). There were 37 soil map units totaling 1,617 acres (5.6 percent of the entire upper watershed area) with predicted soil erosion rates above a sustainable rate. In Perry Creek watershed, these sites were located on steep slopes tangent to streams. Along the main-stem of Santa Rosa Creek these sites were found in the headwaters where on average slopes are steep, soils are shallow, and rock outcrops exist. There appeared to be no relationship between predicted high soil erosion rates and mapped upland erosion sites, however upland erosion features could not be identified where vegetation canopy restricted view of the soil surface. Additionally, RUSLE2 predicts rill and interrill erosion while upland erosion sites identified using GIS identified larger erosion features, such as gullies. Correlations between predicted soil erosion rates and vegetation formations were confirmed with shrub and tree formations having the highest average predicted soil erosion values. In addition, there was a moderate positive correlation between slope percent and predicted soil erosion (r=0.76), affirming that predicted soil erosion rates increased with increasing slopes.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-08-15T15:18:46Z No. of bitstreams: 1 Waldemir Pereira de Souza.pdf: 2049790 bytes, checksum: cfb86b171794e47f98d211aa32854b10 (MD5)<br>Made available in DSpace on 2016-08-15T15:18:46Z (GMT). No. of bitstreams: 1 Waldemir Pereira de Souza.pdf: 2049790 bytes, checksum: cfb86b171794e47f98d211aa32854b10 (MD5) Previous issue date: 2015-09-18<br>Soil erosion is an irreversible phenomenon that causes soil degradation and deterioration of water quality, therefore, models such as water erosion prediction project (WEPP) physical base can be increasingly used to assess erosion rill in semiarid environment. The objective was to quantify the rill erosion with relationships the WEPP and evaluate the hydraulic conditions of runoff under conditions of rill preformed. The experiment was conducted in the exu watershed in Serra Talhada, semiarid region of Pernambuco where was prepared 16 rill preformed who underwent different flow levels: 5.87 L min-1, 12.10 L min-1, 20.33 L min-1 and 27.57 L min-1 in Entisol fluvent. With the performance of the concentration of runoff in rill experimental produced flow regimes slow turbulent in the largest flows applied characterizing the characterizing the occurrence of erosion in rill. The erodibility values in rill (Kr)was 0.0011 kgN-1s-1 and critical shear corresponds to 1.91 Pa. The values of soil losses to erosion rill were considered high for Entisol fluvent behaving smaller particle size composition with a higher percentage of sand.<br>A erosão do solo é um fenômeno irreversível que causa a degradação do solo e a deterioração da qualidade da água, dessa forma, modelos como o Projeto de Predição de Erosão Hídrica (WEPP) de base física podem ser cada vez mais utilizados na avaliação da erosão do solo em sulcos em ambiente semiárido. Objetivou-se quantificar a erosão em sulcos com as relações de erosão do WEPP e avaliar as condições hidráulicas do escoamento superficial sob condições de sulcos pré-formados. O experimento foi realizado na Bacia do Riacho Exu, no município de Serra Talhada, região semiárida de Pernambuco onde foram preparadas parcelas experimentais que consistiram em 16 sulcos pré-formados que foram submetidos a aplicação de diferentes níveis de vazão: 5,87 Lmin-1, 12,10 Lmin-1, 20,33 Lmin-1 e 27,57 Lmin-1 em Neossolo Flúvico. Com a atuação da concentração do escoamento superficial nos sulcos experimentais produziram regimes de escoamento na faixa de turbulento lento nos maiores fluxos aplicados caracterizando a ocorrência da erosão em sulcos. Os valores de erodibilidade em sulcos (Kr) foi de 0,0011 KgN-1s-1 e a tensão crítica de cisalhamento corresponde a 1,91 Pa. Os valores das perdas de solo para a erosão em sulcos foram consideradas altas para um Neossolo Flúvico comportando menor composição granulométrica com maior percentagem de areia.

Submitted by GRENDA HINGRID ALCANTARA (grendaalcantara@outlook.com) on 2018-10-04T10:38:02Z No. of bitstreams: 1 Dissertação Grenda.pdf: 1551203 bytes, checksum: b29f515793930c19d42450e6fb2bd2c6 (MD5)<br>Rejected by Neli Silvia Pereira null (nelisps@fcav.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: 1 - A ficha catalográfica e o certificado de aprovação estão em ordem invertida. Primeiro vem a ficha e depois o certificado. 2- Está faltando o resumo em inglês no repositório. Agradecemos a compreensão. on 2018-10-04T14:53:32Z (GMT)<br>Submitted by GRENDA HINGRID ALCANTARA (grendaalcantara@outlook.com) on 2018-10-04T22:12:52Z No. of bitstreams: 1 Dissertação Grenda imprimir .pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5)<br>Approved for entry into archive by Neli Silvia Pereira null (nelisps@fcav.unesp.br) on 2018-10-08T17:15:49Z (GMT) No. of bitstreams: 1 alcantara_gh_me_jabo.pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5)<br>Made available in DSpace on 2018-10-08T17:15:49Z (GMT). No. of bitstreams: 1 alcantara_gh_me_jabo.pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) Previous issue date: 2018-07-11<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Em modelos de predição da erosão, caso do Water Erosion Prediction Project – WEPP, há a necessidade da determinação de propriedades do solo relativas à sua resistência à erosão. Deste modo, o objetivo deste trabalho foi determinar a erodibilidade em sulcos (Kr) e a tensão cisalhante crítica (tc) em Latossolos com diferentes teores de óxidos de ferro na região nordeste do Estado de São Paulo. A erosão em sulcos foi avaliada com chuva simulada de intensidade média de 65 mm h-1 aplicada por 65 minutos, além de fluxos adicionais de água (11, 39 e 64 L min-1), em seis sulcos pré-formados, em cada Latossolo, com 9,0 m de comprimento, 0,10 m de profundidade e 0,25 m de largura em cada solo. Os valores Kr para os Latossolos foram de 0,0094 s m-1 a 0,0035 s m-1. Os Latossolos mais cauliníticos apresentaram os maiores valores de Kr. Já os valores de tc foram de 2,915 N m-2 a 2,514 N m-2. A razão Ct/(Ct+Gb) explicou 90% das variações na erodibilidade em sulcos e 94% das observadas para a tensão cisalhante crítica nos quatro Latossolos.<br>In erosion prediction models, in the case of the Water Erosion Prediction Project (WEPP), it is necessary to determine the soil properties related to its erosion resistance. Thus, the objective of this work was to determine the RILL erodibility (Kr) and critical shear stress (tc) in Oxisols with different levels of iron oxides in the northeastern region of the State of São Paulo. Furrow erosion was evaluated with simulated rain of 65 mm h-1 mean intensity applied for 65 minutes, as well as additional water flows (11, 39 and 64 L min-1) in six preformed grooves in each Latosol, 9.0 m in length, 0.10 m in depth and 0.25 m in width in each soil. The Kr values for the Oxisols were 0.0094 s m-1 to 0.0035 s m-1. The most kaolinitic Oxisols presented the highest values of Kr. The values of tc were 2.915 N m-2 to 2.514 N m-2. The Ct/(Ct + Gb) ratio explained 90% of the variations in erodibility in grooves and 94% of those observed for critical shear stress in the four Oxisols.<br>CNPQ 143683/2016-0

The Lockheed Fire occurred in August 2009, burning 7,819 acres of the coastal mountains north of Santa Cruz, California. The fire burned a large portion of the Scotts Creek watershed, including over 90 % of the Little Creek watershed, much of which is on Cal Poly’s Swanton Pacific Ranch (SPR). After intense winter rains in 2010 there was a significant amount of hillslope-derived sediment deposited on the roads and in the creek. A large portion of this material was derived from two chaparral hillslopes. These hillslopes were identified as the only two hillslopes within the Little Creek subwatershed where an extensive network of rill erosion had occurred. The purpose of this study was to determine what factors were related to the erosion process on two burned hillslopes. Water repellency, infiltration, saturated hydraulic conductivity, and particle size class were assessed to determine how the impacts of the fire affect the soil physical properties where rill erosion occurred. In order to address this goal, the soil physical properties were characterized on two hillslopes influenced by three different types of parent material: Santa Cruz mudstone, Santa Margarita sandstone and colluvium derived mainly from the Santa Cruz mudstone. The study, consisted of 10 transects and three sampling points at 3, 18 and 27 m, on 45-80% southeastern facing slopes. The vegetation consisted of knobcone pine chaparral mix, transitioning down slope to a chaparral mix. The results showed slope length, clay content and infiltration, were statistically significant. Hydraulic conductivity (Ksat) and slope steepness were not significant, but were included as associated variables with the occurrence of rilling. The study has provided information about post fire soil properties to determine what factors contribute to rill erosion causing the sedimentation into the streams. The observation from the study site can be used in similar conditions within the coastal mountain range setting, thus helping to create models for future planning of the overall watershed management.

Soil erosion is a complex, natural process that often is accelerated by such human activities as land clearance, agriculture, construction, and surface mining. Accurate soil erosion type/intensity maps can be effective tools in aid of soil erosion control efforts.<br>The principal objective of this research was to use geographic information system (GIS) and remotely sensed data to extract and define erosion types/intensities over a large area (4,511.8 km2) in Iran. The study proceeded in three major steps: (i) a 10-m resolution digital elevation model (DEM), land slope, elevation range, and stream network pattern were created. These basic identifying parameters plus Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images were used to differentiate various landforms, (ii) a land use and land cover map was created based on analysis of three Landsat Enhanced Thematic Mapper (ETM+) images from the growing season plus use of a landform map and climatic zones as ancillary information, and (iii) in order to extract and identify various erosion types/intensities, the difference in brightness combination over two growing season intervals derived from the Landsat ETM+ images were used. Further, land slope, landform, land use, and land cover layers were used to assist in the classification of the erosion types (interrill and rill).<br>The approach presented produced soil erosion type/intensity maps with an overall accuracy of 93.4%. Considering only rangeland and forest a unique relationship exists between seasonal brightness combinations and erosion intensity. It was found that for the lower erosion levels it is the later season or second brightness combination (BJS) which indicates degree of erosion intensity, but for the areas of severe and very severe erosion it is the early season or first brightness combination (BMJ) that differentiates degree of erosion intensity. Further, this study illustrated that land use, land cover, landform, and land slope layers can be used for differentiating erosion types.<br>The approach presented has been shown to be an effective tool for the creation of soil erosion maps over a large area of Iran and is expected to be useful for aiding in the development of soil conservation and watershed management plans in other areas. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world.<br>Processus naturel complexe, l'érosion du sol est fréquemment exacerbée par les activités anthropiques telles le défrichage, l'agriculture, la construction, et l'exploitation minière à ciel ouvert. Une cartographie précise du type et de l'intensité d'érosion du sol peut s'avérer un outil efficace dans une lutte contre l'érosion.<br>Les présentes recherches visèrent l'utilisation de SIG et de données de télédétection dans la localisation et l'identification de divers types d'érosion sur une aire de grande étendue (4,511.8 km2) en Iran. L'étude s'échelonna sur trois étapes: (i) un modèle altimétrique numérique (MAN) d'une résolution de 10 m servit à créer des plans de pente du terrain, d'altitude, et du tracé hydrographique. Différentes formes de relief furent différenciés grâce à ces paramètres identificateurs et à des images provenant de radiomètre spatial de pointe pour l'étude de la réflectance et des émissions thermiques terrestres (ASTER), (ii) une carte d'affectation et de couvert du sol fut tracée selon l'analyse de trois images Landsat ETM+ prises durant la saison de croissance ainsi que des informations supplémentaires tirés de cartes de relief et de zones climatiques, et (iii) la différence dans la combinaison de brillances provenant d'images Landsat ETM+, lors de deux intervalles de la saison de croissance, servit à extraire et identifier les différents types et intensités d'érosion. Les plans de pente du terrain, de relief, ainsi que ceux d'affectation et couvert du sol, appuyèrent l'identification du type d'érosion (rigoles et entre-rigoles).<br>Cette approche généra des cartes de type et d'intensité d'érosion d'une exactitude globale de 93.4%. Ne prenant en compte que les parcours et forêts, il devient apparent qu'il existe un lien tout particulier entre la combinaison de brillances saisonnières et le taux d'érosion. Pour les niveaux d'érosions moins élevés c'est la seconde combinaison de brillances (BJS), qui prévale en fin de saison, qui est la plus fortement liée au niveau d'intensité de l'érosion, tandis que pour les zones d'érosion sévères et très sévères c'est la première combinaison de brillances (BMJ), qui prévale en début de saison, qui permet de différencier le niveau d'intensité de l'érosion. Cette étude indique que l'affectation et le couvert du sol, le relief et les pentes du terrain peuvent servir à différencier divers types d'érosion.<br>Nous avons démontré que la démarche préconisée représente un outil efficace dans la création de cartes d'érosion à grande échelle pour l'Iran, et nous nous attendons qu'elle s'avèrera utile au développement de politiques de conservation du sol et de gestion des bassins versants dans d'autres régions. Les principaux avantages de cette démarche sont sa précision, ses moindres exigences au niveau du temps sur le terrain et coûts associés, ainsi que la disponibilité accrue des données nécessaires de par le monde.

Der Einfluss bodenspezifischer Größen auf die Rillenerosion wurde in Überströmungsversuchen in einem eigens dafür konstruiertem Kleingerinne untersucht. Die Neigung des 2 m langen und 0,1 m breiten Gerinnes wurde dafür zwischen 2, 4 und 6 % variiert. Im Gerinne wurden zum einen natürliche Böden, zum anderen künstliche, aus Schluff und Sand gemischte Substrate mit 0,060 l*s-1, 0,125 l*s-1 und 0,300 l*s-1 überströmt. Die Körnung der natürlichen Böden reichte von stark schluffig bis sandig-lehmig, die der künstlichen Substrate von stark schluffig bis sandig. Die künstlichen Substrate wiesen im Gegensatz zu den natürlichen Böden keine Aggregierung auf und waren frei von organischer Substanz. Zu Beginn der Versuche wird der Boden zunächst flächig überströmt. Währenddessen bilden sich Mikrorillen auf der Gerinnesohle aus. Selektiver Sedimenttransport bewirkt die Akkumulation der nicht transportablen Fraktion auf der Bodenoberfläche, wodurch sich Rippel bilden. Über den Rippeln formen sich stehende Wellen im Abfluss. Die stehenden Wellen erzeugen Sohlschubspannungsspitzen auf die Gerinnesohle, welche zu verstärkter lokaler Erosion, zur Ausbildung von Mikrodepressionen und im weiteren zur Entstehung von Rillenköpfen führen. Die Rillenköpfe wandern entgegen dem Gefälle und hinterlassen Rillen, in denen sich der Abfluss konzentriert. In den Rillen können weitere Rillenköpfe entstehen. Anhand des Beginns der Rillenerosion, der Rillenkopfneubildungsrate, dem Erosionsfortschritt der Rillenköpfe, der Bestandsdauer der Rillenköpfe und der Sedimentkonzentration im Abfluss kann das Phänomen „Rillenerosion“ erfasst und quantifiziert werden. Diese erosionsspezifischen Kennwerte zeigen sich dabei in Abhängigkeit von bodenspezifischen Größen, wie der Lagerungsdichte, der Korngrößenzusammensetzung sowie der Aggregatgrößenverteilung und –stabilität. Aus den Korrelationsanalysen zwischen den bodenspezifischen Größen und den spezifischen Kennwerten der Rillenerosion leiten sich empirische Beziehungen ab. Diese Beziehungen sind nicht-linearerer und nicht-stetiger Natur. Parallel zu den Versuchen im Kleingerinne wurden Überströmungs- und Beregnungsversuche in einem Großgerinne durchgeführt. Die Projektion der laborativen Ergebnisse des Kleingerinnes auf das naturnahere Großgerinne zeigte dabei Parallelen.

Concentrated flow erosion in rills, pipes, ephermal gullies, and gullies is a major contributor of downstream sedimentation. When rill or gullies form in a landscape, a 3- to 5-fold increase in soil loss commonly occurs. The balance between the erosive power of the flow and the erosion resistance of the bed material determines the rate of concentrated flow erosion. The resistance of the bed material to detachment depends primarily on the magnitude of the interparticle forces or cohesion holding the particles and aggregates together. The effect of soil properties on bed material resistance and concentrated flow erosion was evaluated both in the laboratory and field. Both rill erodibility and critical hydraulic shear were greater when measured in 9.0 m long rills under field conditions compared with laboratory mini-flumes. A greater hydraulic shear was required to initiate erosion in the field compared to the mini-flume because of the greater aggregate and clod size and stability. Once erosion was initiated, however, the rate of erosion as a function of hydraulic shear was greater under field conditions because of the greater potential for slaking upon wetting and the greater soil surface area exposed to hydraulic shear. Erosion tests under controlled laboratory conditions with the mini-flume allowed individual soil variables to be studied. Attempts to relate rill erosion to a group soil properties had limited success. When individual soil properties were isolated and studied separately or grouped separately, some trends were identified. For example, the effect of organic carbon on rill erodibility was high in kaolinitic soils, low in smectitic soils, and intermediate in the soils dominated by illite. Slow prewetting and aging increased the cohesion forces between soil particles and decreased rill erodibility. Quick prewetting increased aggregate slaking and increased erodibility. The magnitude of the effect of aging depended upon soil type. The effect of clay mineralogy was evaluated on sand/clay mixtures with montmorillonite (M), Illite (I), and kaolinite (K) clays. Montmorillonite/sand mixtures were much less erodible than either illite or kaolonite sand mixtures. Na-I and Na-K sand mixtures were more erodible than Ca-I and Ca-K due to increased strength from ionic bonding and suppression of repulsive charges by Ca. Na-M was less erodiblethan Ca-M due to increased surface resulting from the accessibility of internal surfaces due to Na saturation. Erodibility decreased when salt concentration was high enough to cause flocculation. This occurred between 0.001 mole L-1 and 0.01 mole L-1. Measuring rill erodibility in mini-flumes enables the measurement of cohesive forces between particles and enhances our ability to learn more about cohesive forces resisting soil detachment under concentrated water flow.