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Precision Conservation With Geospatial Technologies
T.G. Mueller, S. A. Shearer
Department of Plant and Soil Sciences
The NRCS provides substantial payments through the conservation reserve program (CRP) to land owners who have conservation buffers installed and maintained. This is because these structures have been shown to prevent ephemeral gully erosion which accounts for a substantial amount of the total water erosion that occurs in agricultural fields.
To determine whether CRP-eligible grassed waterways can be established in agricultural fields, an NRCS conservationist must first make an on-farm site assessment. This involves walking across fields in order to identify areas where there is evidence of erosion resulting from concentrated water flow. This is a slow and time-consuming process and eroded channels scattered across large fields can easily be missed. Given contracting budgets and growing responsibilities of NRCS conservationists, they have less time to make these field visits. Tools are needed that will help them rapidly and accurately identify areas that are eligible to receive CRP payments for these conservation structures.
We are developing neural network and regression models to predict the erosion from concentrated flow. Terrain attributes are used as predictor variables such as LS (length slope factor), WET (topographic wetness index), and PLAN (Plan curvature) are terrain attributes derived from precision GPS measurements. Cost effective mapping procedures will be developed in order to help NRCS conservationists more rapidly identify and prioritize potential locations for grassed waterways and buffer strips for enrollment in CRP. These maps will be similar to the one presented in Fig.1. , but in addition to estimating the potential erosion associated with each feature, we will also estimate the potential for delivering sediment beyond the edge-of-field and will estimate the potential for sequestration of carbon.
Furthermore, we will we will evaluate the accuracy of prediction maps created using elevation data sources that differ in spatial resolution: USGS digital elevation models (DEMs) and light detecting and ranging (LIDAR). LIDAR data is much less expensive than surveys created from precision GPS measurements on a per hectare basis. The USGS DEMs are freely available on the internet. However, the adequacy with which prediction maps can be created from these datasets is unknown but preliminary results suggests that USGS data will be adequate in some cases. We will determine how these models should be parameterized across the different physiographic regions in Kentucky.
We expect this work to lead to the development of regional models that predict where waterways will be needed. We hope that these maps of erosion potential will be on the internet and available to government personnel, farmers, and citizens.
2010 Project Description
We analyzed LiDAR elevation data collected in December of 2009. We used this to calculate terrain attributes (slope, aspect, curvature, topographic wetness index). We created scripts to automated analyses in command line TauDEM.
Next we developed GIS techniques to estimate how wide vegetative buffer should be to reduce off-site sediment deliver to a user defined level (e.g., 90%). This analysis was automated with ArcGIS Model Builder.
We are working to use terrain analysis techniques to identify grassed waterways using GIS and digital terrain analysis techniques. We have found that elevation data from RTK gps and freely available 10-m USGS digital elevation models (DEMs) can be used to identify concentrated flow pathways in agricultural fields in order to minimize concentrated flow erosion.
This work is critically important because concentrated flow contributes to 40% of total erosion that occurs in agricultural fields. It currently cannot be predicted with the erosion models used by conservation planners (e.g., RUSLE2, WEPP). Our work in this area has resulted in two new refereed journal publications this year. Additionally, I received funding to explore the use of LiDAR to identify these eroded features.
This project has expanded to also involve using terrain analysis to help design variable width vegetative buffers. Mueller is working with riparian ecologist, Mike Dosskey, from the USDA forest service to develop and improve a set of procedures to vary filter strip width by combining model predictions of off-site nutrient loading with GIS and terrain analysis techniques. This work has resulted in one proceedings paper and two presentations at national meetings. We have been invited to present this work in a 2011 special edition of the Journal of Soil and Water Conservation Society on the topic of "precision conservation." Mueller has received funding from the USDA-forest service to expand this work using LiDAR and automate the processing of the GIS analyses.
Pike, A.C., T.G. Mueller, A. Schorgendorfer, J.D. Luck, S.A. Shearer, and A.D. Karathanasis. 2010. Locating eroded waterways with United States Geologic Survey Elevation Data. Agron. J.102:1269-1273.
Luck, J.D., T.G. Mueller, S.A. Shearer, and A.C. Pike. 2010. Grassed Waterway Planning Model Evaluated for Agricultural Fields in the Western Kentucky Coal Field Physiographic Region of Kentucky. JSWC. sept/oct 2010: 65:280-288.
Dosskey, M.G., and T.G. Mueller. 2010. Designing variable-width filter strips using GIS and terrain analysis. In R. Khosla (ed.) Proc. 10th International Conference on Precision Agriculture and other Precision Resources Management. ASA Misc. Publ., ASA, CSSA, and SSSA, Madison, WI. Published on CD.