Court Creek Watershed - Hydrologic Unit 52 [3.6 x 4.6km]

Analysis of soil erosion and deposition by water for different conservation strategies

Helena Mitasova, University of Illinois at Urbana-Champaign,

click on the images to see the maps of land use, soil detachment and erosion/deposition
CAUTION! NUMBERS ARE RELATIVE! NO FIELD CALIBRATION OR VALIDATION WAS DONE!

add basic topo map (elevation, roads, streams, urban, etc) here

land use
legend		 %agriculture (row crops)
Cfac legend		 soil detachment:
total[1000t]/average[t/ay] legend[t/ay]		 soil erosion/deposition: excess[1000t] legend[t/ay] comments
bare N/A
 10,500  /  62 77
 X
corn 100   5,200  /  31
 38
X
60 ft stream buffer 96
   4,800  / 28
 19
 only big streams have buffers
100 ft stream buffer 94
   4,600  / 27 19
 only big streams have buffers
60ft stream buffer, forest on slopes > 10% 81
   2,000  / 12 15
 X
current 63
   1,300  / 8 4
 grains on steep slopes add to erosion - possible error in LU?
model-based, forest/dense grass where A>10 58
    200  /  1.2 0.1
 almost the same % of agriculture as current, but some are in too small patches

Computed with GRASS5 under LINUX using modified USLE3D and USPED models and data from USGS and ILGIS

Comments - the results of the modeling effort indicate that:

1. This area has a very good, conservation oriented land use pattern (e.g. compare current land use with "buffers only" scenario).
2. Soil loss can be further reduced by focusing on headwater areas and areas with concentrated flow (possible gullies, interminent streams)
3. Rules for conservation areas which include both distance from stream and slope steepness are good, however they miss headwaters and concentrated flow.
4. Stream buffers based only on a distance from larger streams do not provide sufficient protection - terrain configuration has to be considered.
5. Erosion/deposition model (USPED) shows significant deposition in valleys and hollows (more than what we usually get from the model). Only after increasing resolution to 5m and smoothing, high erosion typical for gullies starts to show up in the center of depositional areas, which means that at this resolution the erosion from concentrated flow is underestimated and higher resolution is needed to capture it (our previous experience suggests 2-3 m resolution).
6. Modeling spatial distribution of soil detachment and net erosion/deposition can provide valuable information for science based extension/enhancement of rules for conservation program if it is used with appropriate field observations.

This research was supported by the Illinois state agencies and programs: CFAR, IDNR and the development of methods was funded by USA CERL and SERDP

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