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 - this is a technology issue which needs to be resolved.
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.

Data

To further improve the results and run more sophisticated simulations the following data are needed:

1. Streams 1:24,000 or better
2. Current land use at 10m resolution
3. Average C-factors for different land uses
4. Soil map with K-factor
5. As always - any type of validation data, observations, photos etc.

For the presented results in digital form email me at helena@gis.uiuc.edu

Additional results (forthcoming)

1. Erosion and erosion/deposition maps for selected land uses based on DEM computed by RST
2. Results from SIMWE (shows much more water flowing from upland than the model based on r.flow which gets water trapped in pits)

Things to look at

1. water flow and erosion/deposition especially in streams if the fields in flat areas are a) drained (RST-based results and SIMWE indicates that substantial amount of water can be comming from there into the streams); b) without drainage with water accumulating and standing in depressions.

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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