EM 1110-2-2907
1 October 2003
6-12 Case Study 10: Digital Terrain Modeling and Distributed Soil Erosion
Simulation/Measurement for Minimizing Environmental Impact of Military
Training
Subject Area: DEM generation and soil erosion modeling
Purpose: To adequately model soil erosion and transport for land use
management
Data Set: Digital Elevation Models (DEM)
a. Introduction.
(1) The conservation of soil on military land is a priority among land use managers,
second only to the protection of threatened and endangered species. A realistic model of soil
erosion and subsequent transport will provide managers the information required to better
plan military activities, such as training. A better model of the various factors that contribute
to soil loss will give insight into the best temporal and spatial use of military land.
(2) The optimal soil loss model incorporates information regarding the diurnal, sea-
sonal, and temporary elements influencing soil properties, as well as incorporating terrain
details. Prior to this 1997 study, soil loss models tended to measure soil loss along a linear
slope, calculated as the average slope across the study area. Models with these simple slope
inputs do not consider the dynamic nature of slope terrain and its consequential control on
soil erosion, transport, and deposition. The study summarized here attempted to improve
upon existing soil erosion models by incorporating details associated with an undulating sur-
face. The model extracted high resolution terrain information from a digital elevation model
(DEM) to better mimic erosional provenance and sediment sinks within a watershed.
b. Description of Methods. This study applied three sediment erosion/deposition models
to 30- and 10-m DEM data. The models included CASC2D, a two-dimensional rain-
fall/runoff model, USPED, an improved Universal Soil Loss Equation model, and SIMWE
(SIMulated Water Erosion), a landscape scale erosion/deposition model. All models at-
tempted to simulate watershed response to military training scenarios.
(1) The first model, the CASC2D is a two-dimensional rainfall-runoff model that
simulates spatially variable surface runoff. This modeling process can be found in
GIS/remote sensing software packages
(http://www.engr.uconn.edu/~ogden/casc2d/casc2d_home.html). Model inputs include run-
off hydrographs, and water infiltration rate and depth, surface moisture, surface runoff
depth, and channel runoff depth.
(2) The second model, the Revised Universal Soil Loss Equation (RUSLE; see equa-
tion 6-3), is the most widely used empirical erosion model, and is best applied to homoge-
neous, rectangular agricultural fields. The equation quantifies major factors that affect ero-
sion by water. The LS (slope length factor) accounts for only the steepness of the terrain
over a given area. The authors of this study developed an LS analog for the RUSLE and
refined the soil loss equation creating the Unit Stream Power Erosion and Deposition
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