Landscape Assessment of Soil Erosion and Nonpoint Source Pollution

ABSTRACT-The hydrologic processes occurring in the landscape are a manifestation of its topographic attributes. Spatially variable topographic-based attributes permit the distribution of hydrologic and nonpoint source pollution processes to be mapped within catchments. They can be derived from Digital Elevation Models (DEMs) using a variety of Terrain Analysis Methods (TAMs). The relationships between topographic indices and the spatial distribution of the potential for surface runoff, groundwater recharge, soil erosion, and evapotranspiration are graphically illustrated

Modeling Soil Erosion with Emphasis on Steep Slopes and the Rilling Process

A soil erosion model, known as KYERMO, was developed for use in soil erosion research. The model was written in Microsoft FORTRAN, which is a subset of the ANSI FORTRAN 77 standard, allowing the model to be run on an IBM-PC as well as a mainframe computer. The model structure consisted of many interrelated subroutines which facilitated model development, testing, and future expansion. A sensitivity analysis of the detachment component was performed, examining the number of rills, the number of space and time steps, and the detachment parameters. This analysis indicated that the model performed as expected for the detachment limiting case. Field plots for the collection of justification data were designed and constructed on steep slopes (28 and 30.5 percent). Their surfaces were shaped to provide controlled rill patterns. Rainfall was applied through use of an irrigation nozzle rainfall simulator. The field simulations included initial full plot (22.1 m) runs on unrilled surfaces with two and six rill watersheds, full plot runs on established surfaces, and half plot runs on established surfaces. Eight field simulations were conducted. Measured or sampled quantities included runoff rate, delivered sediment concentration, delivered sediment size distribution, rainfall intensity, soil moisture content, plot surface shape, and rill cross-sections. Each of the field erosion events was simulated using KYERMO. Hydrologic parameters were fitted to provide the proper runoff characteristics to allow justification of the erosion component of the model. The detachment parameters were initially set using parameters and relationships from the literature. Prediction was comparable to that reported by other researchers. The detachment parameters were then fitted individually to gain insights about their effects. The resultant values were then considered in light of plot characteristics. These analyses indicated that a more complete knowledge of the rill bed particle size distribution could be used to increase accuracy and that soil structure changes due to tillage should be considered. The detachment rate was found to be the limiting factor rather than the sediment transport rate

Modeling Erosion on Long Steep Slopes with Emphasis on the Rilling Process

A model of soil erosion, known as KYERMO, is presented which emphasizes those processes which are important on steep slopes. Particular emphasis is placed on modeling rill development and geometry since this is the least understood process in erosion mechanics. The model requires an input rill pattern. Rainfall inputs to the model require the use of breakpoint rainfall and kinetic energy. Surface storage is calculated based on random roughness data of Linden (1979). Infiltration is modeled by use of the two layer Green-Ampt-Mein-Larson model as proposed by Moore and Eigel (1981). Runoff is related to rainfall excess and surface storage by the exponential, relationship of Thelin and Keifer (1960). Erosion is modeled separately as rill and interrill erosion. Interrill erosion is modeled by evaluating raindrop splash and interrill transport capacity. Raindrop splash is predicted by using the Bubenzer and Jones (1971) equation which requires kinetic energy, rainfall intensity, and percent clay. In terr ill transport capacity is modeled by either the Yalin (1963) or Yang (1973) equation depending on user preference. The rate of delivery of soil to a rill is a minimum of either the transport rate or splash rate. Rill detachment capacity is calculated using the shear excess equation of Foster (1982). Transport capacity is calculated from either the Yalin (1963) or Yang ( 1973) depending on user preference. The distribution of detachment around the rill boundary is calculated as a function of the shear distribution. Shear is distributed by using a modification of the area method of Lundgren and Jonsson (1964). Rill wall sloughing is calculated by using the procedure of Wu et al. (1982) which uses a critical wall angle. Flow routing in rills is calculated by using the kinematic routing procedures of Brakensiek (1966). Data is presented showing that predictions made with model components are reasonable. A limited sensitivity analysis with the model shows that predictions follow the trends that one would expect

Modeling Surface and Subsurface Stormflow on Steeply-Sloping Forested Watersheds

A simple conceptual rainfall-runoff model, based on the variable source area concept, was developed for predicting runoff from small, steep-sloped, forested Appalachian watersheds. Tests of the model showed that the predicted and observed daily discharges were in good agreement. The results demonstrate the ability of the model to simulate the flashy hydrologic behavior of these watersheds. Five subsurface flow models were evaluated by application to existing data measured at Coweeta on a reconstructed homogeneous forest soil. The five models were: Nieber \u27s 2-D and 1-D finite element models (based on Richards\u27 equation), the kinematic wave equation, and two simple storage models developed by the authors, the Boussinesq and kinematic storage models. All five models performed reasonably well on this homogeneous soil. The coupled infiltration model had a large effect on the simulation results. The cost of running the computer models and the computer memory requirements increased as their complexity increased. Field soil-water and precipitation measurements were made on a small test plot in Robinson Forest, in Eastern Kentucky. These data were used to calculate runoff during four precipitation events and to test three of the subsurface flow models on a natural watershed. Of the models tested, the simple kinematic storage model performed the best. Flow from the test plot was dominated by macropore flow during storm events, and by flow through the soil matrix during baseflow or recession periods. No surface runoff was observed on the test plot during the period of field observations, except on the saturated near-channel source areas; all runoff was initiated by subsurface flow

Fas Regulates Macrophage Polarization and Fibrogenic Phenotype in a Model of Chronic Ethanol-Induced Hepatocellular Injury

The role of Fas-mediated apoptosis and its effect on proinflammatory cytokine production in early alcoholic liver disease has not been addressed. Wild-type mice (C57Bl/6) or mice with a functional mutation in the Fas ligand (B6

The Mission Continues: Engaging Post-9/11 Disabled Military Veterans in Civic Service

The Mission Continues: Engaging Post-9/11 Disabled Military Veterans in Civic Servic

Impacts of the Mission Continues Fellowship Program on Post-9/11 Disabled Military Veterans, Their Families, and Their Communities

Impacts of the Mission Continues Fellowship Program on Post-9/11 Disabled Military Veterans, Their Families, and Their Communitie