Phase I - Model Results by Resource Concern

Overview of the Model Input Layers by Arkansas Natural Resource Concern

The resource concern modeling strategy was mostly dictated by the NRCS national directives with some modifications allowing for the use of available local data, input from the collective experiences of the NRCS conservation partners and preliminary research and analysis completed during 2010. The Arkansas SRA project team was fortunate to have begun research and data collection during 2010; well before the NRCS national directives had been conceived and distributed in April 2011. During this preliminary phase of the Arkansas SRA effort meetings were held with NRCS Conservation Partners to discuss possible methods and datasets that would benefit this assessment. Information related to project goals and proposed modeling strategies were disseminated through meetings and presentations to these partners as well as through the project website.

In order to model each of the 29 resource concerns
relevant within Arkansas, existing GIS data and weighting suggestions were collected from the project partners. Summaries and relative weights for each of the proposed binary and classified raster input layers were prepared and submitted to NRCS for review and approval prior to inclusion into each model. These input data layers were selected due to their applicability, availability, and because they were the datasets recommended by State resource concern experts or directly specified within the NRCS National Directives. The Arkansas NRCS Office coordinated with numerous NRCS technical committees responsible for reviewing all datasets identified by project team members. A weighted sum overlay (raster) modeling method was developed within the ArcGIS software environment, and it became a template for how each natural resource concern model would be executed (and later distributed to partners) for the purposes of identifying the extent of each resource concern’s at-risk acreages within Arkansas. The weighted sum overlay methodology was developed so that model results could be repeated and consistent for addressing all resource concerns required by the NRCS national directives.

These overlay models were created so that the NRCS land use designations, specified within the national directives and developed through a reclassification from the 2006 National Land Cover Dataset (NLCD), were used as a weighted multiplier to the collection of simple additive input binary or classified raster layers selected for each natural resource concern. For example, a model could be summarized this way: each binary and classified input raster layer (30-meter resolution) was summed for each individual natural resource concern; the summation of those input raster layers resulted in one additive sum raster layer that was then multiplied by the weight-specific NRCS land use designation raster layer as specified for each individual natural resource concern. If any NLCD land use category was valued zero; those areas would result in a value of zero being assigned to all land areas of that NLCD category within the individual natural resource concern model output. Therefore any land areas covered by a NLCD weighted reclass of zero would result in those land areas being removed from the total potential at-risk area for the natural resource concern being modeled.

Upon the completion of this raster calculation, the federal lands mask (all federals lands; plus a 300-foot buffer) was applied. This multiplication mask essentially extracted or removed those land areas from the final resource concern model result map because it was simply a reclassification of those land areas within the federal lands mask as zero. Since NRCS conservation programs are primarily applied to private lands, the federal lands of Arkansas were excluded from consideration for this analysis. Land use weights are detailed for each natural resource concern model in the Results and GIS Layer Specifications section of this document

The base layer weight for the water land use designation received a weight of zero (0) for all models, except for Soil Erosion – Excessive Bank Erosion from Streams, Shorelines or Water conveyance Channels. The Federal Lands mask (all federal lands; plus a 300-foot buffer) accounts for approximately 13% of all land use designations in Arkansas. Those areas were considered unserviceable or as already receiving conservation treatments from other federal agencies so it was decided that those land areas would be excluded from the At-Risk Area estimates within Arkansas since NRCS conservation programs are primarily focused on private lands.

The natural resource concern model results and the GIS layer specifications for each of these statewide GIS models is summarized within this section of the report. The NRCS leadership team and technical team members that were responsible for GIS layer selection and input layer weight designations for each of the 29 natural resource concerns are also recognized under each of the nine major resource concern headings. These at-risk acres model result maps represent the weighted model output raster layer that identifies the distribution of potential at-risk areas for each natural resource concern. Larger maps for each of these natural resource concern models are included within the appendix. The individual input layer maps for all resource concern models can be viewed online. The calculated area (acres)reflects the potential at-risk acreages within Arkansas and not the acreages to be addressed by NRCS programs during the next planning cycle. The potential at-risk area for each output map was calculated from the resulting raster layers where modeled pixel values were equal to or greater than one. These models were compiled with the best available datasets during the spring of 2011 in response to a National Directives request from NRCS headquarters. Each natural resource concern model from phase I of the Arkansas SRA (including each input layer, its relative weighting scheme and the resulting distribution of modeled results) will be reviewed and possibly refined during phase II of the Arkansas SRA project.

SelectionFile type iconFile nameDescriptionSizeRevisionTimeUser

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Crosswalk, NLCD 2006 to NRCS Land Use Designations  156k v. 5 Oct 9, 2011, 9:20 PM Hanna Ford
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NLCD reclassified using NRCS Land Use Designations  7080k v. 6 May 17, 2011, 9:52 PM Hanna Ford
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NRCS SRA Geospatial Instructions  1480k v. 5 Oct 10, 2011, 8:53 AM Hanna Ford