Best Management Practices (BMPs) are conservation practices designed by Natural Resource Conservation Service to help mitigate erosion and nutrient losses in agriculture. Water and Sediment Control Basins (WASCoBs) are BMPs implemented in agriculture fields with sloping topography that are susceptible to erosion to help reduce sediment and nutrient losses. There is little research examining the water quality impacts of WASCoBs and their ability to decrease nutrients in water runoff. Runoff samples were collected following intense rain events in seven basins and analyzed for total suspended soils (TSS), total phosphorus, dissolved reactive phosphorus (DRP), ammonium-nitrogen, and nitrate-nitrogen. Nutrient and sediment concentrations and discharge measurements were used to determine event loads for each basin. The WASCoBs trapped an average of 63.4% of TSS, 30.5% of total phosphorus, 15.3% of DRP, 21.8% of ammonium-nitrogen, and 62.9% of nitrate-nitrogen. An Unmanned Aerial Vehicle (UAV) was used to estimate sedimentation rates and proved to be less effective for annual sediment estimates, but perhaps more accurate on a multi-year basis. A detailed soil assessment was performed on all thirty-two basins to estimate short-term legacy phosphorus accumulation. The thirty-two basins trapped an average of 5,403.0 kg/ha of sediment and 16.8 kg/ha of phosphorus. An average of 22 mg kg-1 of total phosphorus accumulated across the basins in one year of sediment accumulation. Potential crop yield penalty was investigated to see the impact between inside the basins compared to the surrounding area. Corn had a decrease of 5.1% yield and soybeans had a decrease of 36.9% in yield inside the basins.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Accelerated soil erosion is drawing a growing attention with the recognition that the rate of soil loss is too great to be met by soil formation rate. Weenen Game Reserve (WGR) is an area with an unfortunate history of prolonged soil erosion due to excessive overgrazing that led to severe land degradation with prominent visible scars. This problem triggered the general objective of estimating and mapping potential soil erosion in WGR. Assessing soil loss in the area objectively has important implications for the overall management plans as it is reserved for ecological recovery. The most important variables that affect soil erosion are considered as inputs in soil loss estimation models. In this study the RUSLE model, which uses rainfall, soil, topography, and cover management data, was employed. From the rainfall data, an erosivity factor was generated by using a regression equation developed by relating EI30 index and total monthly rainfall. The soil erodibility factor was calculated using the soil erodibility nomograph equation after generating the relevant data from laboratory analysis of soil samples gathered from the study area. Using exponential ordinary kriging, the point values of this factor were interpolated to fill in the non-sampled areas. The topographic effect, which is expressed as the combined impact of slope length and slope steepness, was extracted from the DEM of the study area using the flow accumulation method. For mapping of the land cover factor, in situ measurements of cover from selected sites were undertaken and assigned values from the USLE table before being related with MSAVI of Landsat 7 ETM+ image. These values were then multiplied to get the final annual soil loss map. The resulting potential soil loss values vary between 0 and 346 ton ha-1 year-l with an average of 5 ton ha-1 year-l. About 58% of the study area experiences less than 1 ton ha-1 year-1 indicating the influence of the highest values on the average value. High soil erosion rates are concentrated in the central part extending as far as the south and the north tips along the eastern escarpments and these areas are the ones with the steepest slopes. The results indicate a high variation of soil loss within the study area. Nevertheless, the majority of the area falling below the average might foresee that the soil erosion problem of the area can be minimized significantly depending largely on soil management. The most important areas for intervention are the medium and low erosion susceptible parts of WGR, which are mainly found in the flatter or gently sloping landscapes. The steepest areas are mostly covered with rocks and/or vegetation and hence less effort must be spent in managing them. Overall, the reported increasing density of the vegetation community in the area that reduces the exposure of soil from the impact of direct raindrops and surface-flowing water must be pursued further. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

MENVSC (Geography) / Department of Geography and Geo-Information Sciences / Environmental degradation is a quite familiar factor of the mining industry that has been associated with South African mining industry from the beginning. The decommissioning of abandoned mines before the environment legislation, The National Environmental Management Act 107 of 1998 and the Minerals and Petroleum Resources Development Act 23 of 2002, was introduced is of great concern as the abandonment of mines without appropriate remediation and pollution monitoring was the result. Soil erosion has been recognised as an environmental hazard that emanates from abandoned mines. This study seeks to assess the soil erosion hazard around Nyala abandoned mine. The modified method of Soil Loss Estimation Model for Southern Africa (SLEMSA), for assessing soil erosion hazard, was used to estimate the spatial variation of erosion to achieve the goal of the study. Parameters that were considered for the model include relief (Slope steepness, S & slope length, L), soil erodibility (Fb), vegetation cover (C) and rainfall erosivity (E). Soil samples were collected from the field and; sieve and hydrometer analysis was conducted to determine the erodibility factor value of the study area. The model was run in a GIS environment (ArcGIS) and the parameters were multiplied to generate a soil erosion hazard map for the abandoned Nyala mine area. Results from the study indicated that 74.3 % of the watershed experiences low to moderate erosion hazard, with an estimated annual soil loss of 2.76 tons/ha/yr. The low rates of soil erosion in most parts of the watershed are associated with the low topographic ratio and low rainfall erosivity. The research demonstrated that the modified SLEMSA model used within GIS is a very useful tool as it enhances the capacity to assess and model the spatial variation of soil erosion hazard in a timeously and affordable manner. / NRF

by Leung, Yu-fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 167-178). / abstract --- p.ii / acknowledgements --- p.iv / table of contents --- p.vi / list of tables --- p.ix / list of figures --- p.xi / list of plates --- p.xiii / Chapter CHAPTER I --- introduction / the problem --- p.1 / The Country Parks of Hong Kong --- p.1 / Resource Impacts of Country-Park Recreation --- p.3 / Trail Degradation --- p.4 / objectives of the study --- p.5 / scope of the study --- p.6 / Chapter CHAPTER II --- literature review / introduction --- p.8 / research approaches --- p.9 / physical degradation on trails --- p.11 / Compaction / Widening and Incision / Erosion --- p.16 / FACTORS CONTRIBUTING TO TRAIL DEGRADATION --- p.17 / Use Characteristics --- p.19 / Environment --- p.20 / RECREATION IMPACT STUDIES IN HONG KONG --- p.21 / Chapter CHAPTER III --- study area / introduction --- p.24 / the pat sin leng country park --- p.24 / "Topography,Geology and Soils" --- p.25 / Climate and Vegetation --- p.29 / Recreational Use and Management --- p.31 / the pat sin range trail --- p.35 / Chapter CHAPTER IV --- research methodology / introduction --- p.41 / research design --- p.41 / hypotheses --- p.43 / SAMPLING SCHEME --- p.44 / VARIABLES INCLUDED IN THE STUDY --- p.46 / FIELD MEASUREMENTS --- p.49 / Degradation-Indicator Variables --- p.49 / Site Condition Variables --- p.58 / LABORATORY ANALYSIS --- p.63 / DATA MANIPULATION AND ANALYSIS --- p.65 / Chapter CHAPTER V --- SITE AND DEGRADATION CONDITION OF THE PAT SIN RANGE TRAIL / INTRODUCTION --- p.67 / SITE CONDITION OF THE TRAIL --- p.67 / Parent Material --- p.67 / Topography --- p.72 / TREAD SURFACE MATERIAL --- p.80 / COMPACTION OF TRAIL TREAD --- p.82 / MORPHOLOGY OF TRAIL TREAD --- p.90 / Tread width --- p.91 / Incision Depth --- p.94 / Tread Cross-Section Area --- p.96 / Multiple Treads --- p.96 / Other Morphology Variables --- p.98 / OVERALL EVALUATION --- p.98 / Other Evidence of Degradation --- p.98 / Summary Rating --- p.101 / REMARKS --- p.106 / Chapter CHAPTER VI --- ENVIRONMENTAL INFLUENCES ON TRAIL DEGRDATION / INTRODUCTION --- p.107 / BRANCHING EFFECT OF TRAILS --- p.108 / PARENT MATERIAL --- p.112 / Parent Rock --- p.112 / Soil Properties --- p.115 / LOCATIONAL FACTORS --- p.120 / Aspect --- p.120 / Slope Steepness --- p.124 / Trail Position on Slope --- p.136 / OVERALL EVALUATION --- p.145 / Chapter CHAPTER VII --- MANAGEMENT IMPLICATIONS / INTRODUCTION --- p.151 / MANAGEMENT CONSIDERATIONS --- p.152 / THE CASE OF PAT SIN RANGE TRAIL --- p.153 / MONITORING TRAIL USE AND IMPACTS --- p.159 / Chapter CHAPTER VIII --- CONCLUSION / SUMMARY OF FINDINGS --- p.162 / LIMITATION OF THE STUDY --- p.164 / SUGGESTIONS FOR FUTURE RESEARCH --- p.164 / BIBLIOGRAPHY --- p.167 / APPENDIX / DESCRIPTIONS OF SELECTED DEGRADED SITES --- p.179

by Choi Chi Hoi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Bibliography: leaves 171-178. / ABSTRACT --- p.iii / ACKNOWLEDGMENTS --- p.v / TABLE OF CONTENT --- p.vi / LIST OF FIGURES --- p.x / LIST OF TABLES --- p.xii / LIST OF PHOTOS --- p.xiv / LIST OF APPENDICES --- p.xvi / Chapter I --- INTRODUCTION / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Objectives --- p.6 / Chapter 1.3 --- Uniqueness and Significance of the Study --- p.7 / Chapter 1.4 --- Some Key Concepts --- p.9 / Chapter 1.5 --- Organization of the Thesis --- p.11 / Chapter II --- THE STUDY AREA / Chapter 2.1 --- Selection of the Study Area --- p.12 / Chapter 2.2 --- The Physical and Socio-Economic Environment of the Deqing County --- p.17 / Chapter 2.2.1 --- Location --- p.17 / Chapter 2.2.2 --- Climate --- p.17 / Chapter 2.2.3 --- Geology and Landform --- p.18 / Chapter 2.2.4 --- Vegetation --- p.18 / Chapter 2.2.5 --- Population and Economic Activities --- p.19 / Chapter 2.2.6 --- History of Soil Erosion and Conservation --- p.21 / Chapter 2.3 --- The Shenchong Basin --- p.26 / Chapter 2.4 --- The Lichong Basin --- p.28 / Chapter 2.5 --- The Resource Base of Deqing --- p.30 / Chapter III --- METHODOLOGY --- p.34 / Chapter 3.1 --- Conceptual Considerations --- p.34 / Chapter 3.2 --- Land Degradation Processes --- p.35 / Chapter 3.2.1 --- Nutrient Loss from Hillslopes --- p.38 / Chapter 3.2.2 --- Iron Toxicity --- p.43 / Chapter 3.2.3 --- Properties and Nutrient Status of Rehabilitated Soils --- p.44 / Chapter 3.2.4 --- Methods of Chemical Analysis of Water and Soil Samples --- p.49 / Chapter 3.3 --- Cost-Benefit Analysis of Rehabilitation Measures --- p.50 / Chapter 3.4 --- Problems and Limitations --- p.54 / Chapter IV --- LAND DEGRADATION： PROCESSES AND PROBLEMS --- p.56 / Chapter 4.1 --- Landscape Changes in a Severely Eroded Granitic Area --- p.56 / Chapter 4.2 --- Land Degradation Processes 一 On-site Effects --- p.60 / Chapter 4.2.1 --- Soil Loss on the Hillsides --- p.60 / Chapter 4.2.2 --- Loss of productivity on the Hillsides --- p.64 / Chapter 4.3 --- Land Degradation Process - Off-Site Effects --- p.70 / Chapter 4.3.1 --- Burial of Agricultural Land Beneath Alluvial Fans --- p.70 / Chapter 4.3.2 --- Concentration of Dissolved Iron in Sub-surface Water --- p.74 / Chapter 4.4 --- Concluding Remarks --- p.78 / Chapter V --- COST-EFFECTIVENESS OF EROSION CONTROL MEASURES THEORETICAL CONSIDERATIONS --- p.80 / Chapter 5.1 --- Introduction --- p.80 / Chapter 5.2 --- Economic-Biophysical Management Linkages in the Shenchong Basin --- p.80 / Chapter 5.3 --- Range of Erosion Control/Land Use Options --- p.83 / Chapter 5.4 --- Methodology --- p.83 / Chapter 5.4.1 --- Data Sources --- p.85 / Chapter 5.4.2 --- Economic Valuation Techniques --- p.85 / Chapter 5.5 --- Cost-Effectiveness Evaluation of Erosion- Control Measures --- p.87 / Chapter 5.5.1 --- Option 1 - Hillsides are Maintained Under Dense Fern and Tree Cover and No Use is Permitted --- p.88 / Chapter 5.5.2 --- Option 2 : Slope - Maintaining Dense Vegetation Cover but Permitting Sustained Yield Harvesting of Fern for Fuel and Resin and Timber Production --- p.90 / Chapter 5.5.3 --- Option 3 : Slope - Building Terraces on Hillslopes --- p.92 / Chapter 5.5.4 --- Option 4 : Slope - No Erosion Control Measures --- p.94 / Chapter 5.5.5 --- Option 5 : Slope - Conversion from Fern and Woodland to Baji and Yu Gui Crops --- p.94 / Chapter 5.5.6 --- Option 6 - Small Check Dams Constructed to Control Gully Erosion --- p.94 / Chapter 5.5.7 --- Option 7 : Gully - Large Check Dams --- p.97 / Chapter 5.5.8 --- Option 8 : Gully - Biological Dams --- p.98 / Chapter 5.5.9 --- Option 9 : Gully - Infilling of Gullies --- p.99 / Chapter 5.5.10 --- Option 10 : gully - No Erosion Control --- p.100 / Chapter 5.6 --- Policy Implications --- p.100 / Chapter 5.7 --- Policy Optimization With Multiple-Objective Decision Modeling --- p.102 / Chapter VI --- REHABILITATION PROGRAM AT SHENCHONG AND LICHONG RECONSIDERED --- p.107 / Chapter 6.1 --- Introduction --- p.107 / Chapter 6.2 --- Land Rehabilitation at Shenchong --- p.107 / Chapter 6.3 --- Land Rehabilitation at Lichong --- p.111 / Chapter 6.4 --- Ecological Considerations --- p.119 / Chapter 6.5 --- Agricultural Considerations --- p.124 / Chapter 6.5.1 --- Chemical Soil Properties --- p.126 / Chapter 6.5.2 --- Physical Soil Property --- p.135 / Chapter 6.6 --- Economic Considerations --- p.143 / Chapter 6.6.1 --- Costs and Benefits of Rehabilitation Activities --- p.144 / Chapter 6.6.2 --- Sustainability of the Rehabilitation Programs --- p.146 / Chapter 6.6.3 --- Distribution of Costs and Benefits over Time --- p.148 / Chapter 6.7 --- Institutional Considerations --- p.151 / Chapter 6.7.1 --- Rural Economic Reform --- p.152 / Chapter 6.7.2 --- Institution Set-up of the Two Brigades --- p.153 / Chapter 6.7.3 --- Distribution of Cost and Benefits --- p.154 / Chapter 6.7.4 --- Risk Management --- p.155 / Chapter 6.7.5 --- Land Use Planning --- p.156 / Chapter 6.7.6 --- Motivation --- p.157 / Chapter 6.7.7 --- The Search for Solution --- p.159 / Chapter VII --- CONCLUSION --- p.162 / Chapter 7.1 --- Introduction --- p.162 / Chapter 7.2 --- Discussion --- p.166 / BIBLIOGRAPHY --- p.171 / APPENDICES --- p.179

published_or_final_version / Geography and Geology / Master / Master of Philosophy

Round Island is a small (208 ha) islet of volcanic origin located 22.5 km north east of mainland Mauritius and has been classified as a nature reserve since 1957. Two sites were chosen for the installation of environmental monitoring equipment. A series of Gerlach troughs were installed to capture surface sediment transported by runoff, which were used to document sediment yields and determine the particle size distribution. Overall, rainfall and erosivity on Round Island is far less, when compared to mainland Mauritius. However, erosivity from Round Island (2,314.76 MJ.mm.ha-1.h-1.yr-1) is slightly above the global average of 2,190 MJ.mm.ha-1.h-1.yr-1. In terms of sediment transport, the annual sediment movement rates for Round Island were established during this study (0.1248 t.ha-1.yr-1) and were found to be considerably lower than Mauritius (10 t.ha-1.yr-1), as well as other tropical island such as Kauai (0.86 t.ha-1.yr-1) and O’ahu (0.6 t.ha-1.yr-1). Thus, although the estimated rates of soil erosion are very low for humid tropical regions, these rates only reflect the contemporary environmental conditions and cognisance of the landscape history should be incorporated into assessments of soil erosion / Geography / M. Sc. (Geography)

The effect of eucalyptus forests in hidrossedimentologic processes has been little explored by the scientific community, which results in a database containing information related to these incipient effects, especially at the watershed scale. The monitoring and the mathematical modeling are recognized as effective tools of science to supply the lack of information, particularly in natural resource management, in the representation and prediction of these processes. In this sense, the aim of this study was to describe the monitoring data to assess effects of eucalyptus cultivation in the hidrossedimentological processes, to calibrate the input parameters and to verify the potential application of the Limburg Soil Erosion Model (LISEM) in the representation of watershed hydrological processes embedded with forest cover. The study was conducted in two forest watersheds located in Eldorado do Sul - RS, and the watershed has an area of 94.46 ha and drainage sub-watershed, which is embedded in the amount and terms of the watershed, has a drainage area of 38.86 ha. The hidrossedimentometrical monitoring began in February 2011 and was conducted within the limits of the watershed in two automatic sections, composed of linigraph, turbidimeters and pluviographs. This work has included monitoring over a period of six months from 02/16/2011 to 08/15/2011. The sediment yield was determined by multiplying the data of sediment concentration and flow. The model LISEM was calibrated from six different rain events. The model input parameters were obtained through surveys conducted in the watershed and literature data. To evaluate the model ability in representing the hydrological processes hydrographs measured in the watershed exutory were used. The monitoring results demonstrated that periods with higher rainfall volume presented a significant increase in peak flows in relation to the driest intervals, as well as an increase in the suspended sediments concentration in the watershed and in the sub-watershed. The events with greater rainfall intensity demonstrated that the smallest drainage area of the subwatershed generated faster answers in flow and sediment concentration. For the watershed, in most events occurred flood wave attenuation with least steeply sloping and lowest hydrograph peaks than the sub-watershed. Specifically, the sediment yield was 38.41 and 33.65 t km-2, during the six months of monitoring for the watershed and for the subwatershed, respectively. The magnitude of sediment yield was 0.77 t ha-1 yr-1 for the watershed and 0.67 t ha-1 yr-1 for the sub-watershed. The LISEM model was able to reproduce adequately the peak flow and direct runoff for the six events used for calibration. On the other hand, the peak time and shape of the hydrograph did not have adequate fit. / O efeito das florestas de eucalipto nos processos hidrossedimentológicos tem sido pouco explorado pela comunidade científica, o que resulta em banco de dados contendo informações incipientes relacionadas a esses efeitos, principalmente na escala de bacias. O monitoramento e a modelagem matemática são reconhecidos como eficientes ferramentas científicas para suprir a carência de informações, principalmente na gestão dos recursos naturais, na representação e na predição desses processos. Nesse sentido, objetivou-se com este estudo, descrever os dados do monitoramento, avaliar os efeitos dos cultivos de eucalipto nos processos hidrossedimentológicos, calibrar os parâmetros de entrada e verificar o potencial de aplicação do modelo Limburg Soil Erosion Model (LISEM) na representação dos processos hidrológicos de bacias hidrográficas embutidas, com cobertura florestal. O estudo foi desenvolvido em duas bacias hidrográficas florestais situadas em Eldorado do Sul RS, sendo que a bacia possui área de drenagem de 94,46 ha e a sub-bacia, que se encontra à montante e embutida em relação à bacia, possui área de drenagem de 38,86 ha. O monitoramento hidrossedimentométrico teve início em fevereiro de 2011 e foi realizado no exutório das bacias, em duas seções automáticas, compostas de linígrafos, turbidímetros e pluviógrafos. O presente trabalho contemplou o monitoramento durante um período de seis meses, de 16/02/2011 a 15/08/2011. Os resultados do monitoramento demonstram que os períodos com maior volume de precipitação apresentaram aumento significativo nos picos de vazão em relação aos intervalos mais secos, assim como aumento na concentração de sedimentos em suspensão, para a bacia e para a subbacia. Os eventos com maior intensidade máxima de precipitação demonstraram que a pequena área de drenagem e o relevo mais acentuado da sub-bacia geraram respostas rápidas na vazão e concentração de sedimentos. Para a bacia hidrográfica, na maioria dos eventos, ocorreu amortização da onda de cheia com hidrogramas menos íngremes e ocorrência após o pico de vazão da sub-bacia. A produção de sedimentos foi de 38,41 e 33,65 Mg km-2, durante os seis meses de monitoramento para a bacia e para a sub-bacia, respectivamente. O modelo LISEM foi calibrado a partir de seis eventos de chuva. Os parâmetros de entrada utilizados para o modelo foram obtidos por meio de levantamentos realizados na bacia e de dados da literatura. Para avaliar a capacidade do modelo em representar os processos hidrológicos, foram utilizados hidrogramas medidos no exutório da bacia. A análise estatística aplicada foi o teste BIAS (Erro (%)) para os parâmetros vazão de pico, escoamento superficial direto e tempo de pico. Para avaliar a eficiência do modelo em reproduzir adequadamente o formato dos hidrogramas, foi utilizado o Coeficiente de eficiência Nash-Sutcliffe (COE) para os seis eventos utilizados na calibração. O modelo LISEM foi capaz de reproduzir adequadamente a vazão de pico e o escoamento superficial direto para os seis eventos utilizados na calibração, indicado pelos baixos erros percentuais. Por outro lado, o tempo de pico e a forma do hidrograma não apresentaram ajuste adequado, indicado pelos elevados erros e valores negativos para o erro e para o COE, respectivamente.

A physically based, distributed parameter, event oriented, nonlinear, numerical model of watershed response is developed to accommodate the spatial changes in topography, surface roughness, soil properties, concentrated flow patterns and geometry, and land use conditions. The Green and Ampt equation with the ponding time calculation for an unsteady rain is used to compute rainfall excess rates. The kinematic wave equations are used to describe the unsteady one-dimensional overland and channel flow. The unsteady and spatially varying erosion/deposition process on hillslopes and channel systems is described dynamically using simultaneous rates of sediment entrainment and deposition rather than the conventional approach using steady state sediment transport functions. To apply the model the watershed is represented by a simplified geometry consisting of discrete overland flow planes and channel elements. Each plane or channel is characterized by a length, width, and a roughness parameter. For channel elements, a cross-section geometry is also needed. A modular computer program called WESP (Watershed Erosion Simulation Program) is developed to provide the vehicle for performing the computer simulations. Rainfall simulator plots are used to estimate infiltration parameters, hydraulic roughness, and soil erodibility parameters for raindrop impact and overland flow. The ability of the model to simulate watershed response (hydrograph and sedigraph) to a variety of rainfall inputs and antecedent soil moisture conditions is verified using data collected on two small watersheds. The good agreement between the simulated watershed response and the observed watershed response indicates that the governing equations, initial and upper boundary conditions, and structural framework of the model can describe satisfactorily the physical processes controlling watershed response.