The ACPF Development Team at the USDA/ARS National Laboratory for Agriculture and the Environment, in cooperation with the North Central Region Water Network (NCRWN), are pleased to announce the release of the Agricultural Conservation Planning Framework (ACPF), with enhancements to both the Toolbox and the Database. The current release and accompanying information is available on the ACPF home page at https://acpf4watersheds.org/. To supplement this project, the ISUGISF has also created a tool to download 2 meter DEM by watershed for the state of Iowa.
In order to download DEM, SVI, or ACPF data, you will be asked for some identifying information. These tools will NOT work with Microsoft Edge or Internet Explorer; we recommend using Chrome or Firefox.
The Iowa HUC12 2m DEM database was derived from the original LiDAR point cloud and processed through ArcGIS using the following steps:
- LiDAR point-cloud to points to TIN
- TIN to raster with pyramid thinning
- Conversion to integer cm Z values to address quantization error
- Pit filling to remove one-cell sinks
- Hole punching to remove small (<=10cm) depressions in the DEM
This process results in the P-Class of HUC12 elevation models. This collection has been augmented by performing a partial hydro enforcement using the IA DNR’s stream centerline to create the S-Class library. The process of preparing the stream centerlines for use in hydro modification is as follows;
- Stream features are extracted from the state-wide feature class for the HUC12 watershed
- Features are generalized using the SimplifyLine method using the Bend_SIMPLIFY algorithm and a 10m tolerance
- Resulting features are split at vertices to create individual features with no intermediate vertices
- Very short segments, <= 8.5m, are merged where possible
The resulting features are used as cut lines when an obstruction to flow is present in the DEM that should be "burned through", such as a culvert which routes flow beneath a road. The centerline data were developed from a 1m DEM so there are some minor flow compatibility issues, but the time savings that is realized when involved in the hydro conditioning phase of the toolbox is significant. Average size of the HUC12 2m DEM in a 7Zip archive is 75Mb.
The Iowa ACPF Soil Vulnerability Index (SVI) database includes estimations of soil runoff potential and soil leaching potential for row-cropped fields in each HUC12 watershed. This database was created using the HUC12 Iowa P-Library series LiDAR derived, 2-m DEMs and the ACPF database. These datasets allow for map-unit level estimation of soil runoff potential and soil leaching potential, which can be aggregated to the field-level using the dominant soil class, or the most-limiting soil class. For each soil map unit, slope output is evaluated along with the hydrologic soil group and soil erodibility to classify the runoff potential and, with addition of the ACPF-based coarse fragment content of the soil and the presence of organic soils, to classify the leaching potential. For more detailed information regarding how these metrics are determined, see Thompson et al. (2020).
The downloadable features for each HUC12 in this database include:
- A field boundary feature class; FB<HUC12>
- SVI by-field table; fbSVI<HUC12> -- joinfield: FBndID
- 6-year land use information for each field; LU6_<HUC12>
- Crop history information for each field; CH_<HUC12>
- A gSSURGO soils raster; 10-m resolution
- SVI soil map unit table; muSVI<HUC12> -- joinfield: MUKEY
Within the field-level SVI file geodatabase tables, soil runoff potential and soil leaching potential are represented for both the dominant and most limiting soil class and include an estimate of the percent of the field in those classes. The attributes include;
- DomSRP: Dominant soil runoff potential
- DomSRPpct: Percent of field represented by the dominant soil runoff potential class
- DomSLP: Dominant soil leaching potential
- DomSLPpct: Percent of field represented by the dominant soil leaching potential class
- MLimSRP: Most limiting soil runoff potential
- MLimSRPpct: Percent of field represented by the most limiting runoff potential soil class
- MLimSLP: Most limiting soil leaching potential
- MLimSLPpct: Percent of field represented by the most limiting leaching potential soil
Thompson, A., Baffaut, C., Lohani, S., Duriancik, L., Norfleet, M., & Ingram, K. (2020). Purpose, development, and synthesis of the Soil Vulnerability Index for inherent vulnerability classification of cropland soils. Journal of Soil and Water Conservation, 75(1), 1-11.