Developing Remote Sensing Protocols for Inventory of Permanent Vegetative Practices
An accurate inventory of in-field and off-site nutrient management practices is essential to establish baseline conditions and document implementation of the Iowa Nutrient Reduction Strategy.
This project will develop remote sensing protocols for the inventory and monitoring of two permanent vegetative conservation practices — riparian buffers and grassed waterways.
These protocols will be evaluated in at least three of the initial eight Iowa Water Quality Initiative projects, and more may be added if time permits. To create the baseline conservation practice geodatabase, geographic information systems (GIS) staff will use the Iowa Department of Natural Resources high-resolution land cover product to identify the base conditions for permanent vegetation in the watershed projects. To update the conservation practice geodatabase, newly established practices will be identified. To apply the conservation practice geodatabase, the quality of established practices and potential for new sites will be tested and evaluated. Existing sites will be evaluated for potential effectiveness as nutrient reduction practices.
This project showed grassed waterways are most quickly and accurately assessed by manual heads-up digitizing using elevation data and spring CIR imagery where available. Summer NAIP imagery then can provide either an alternate suitable primary source, or good secondary source for checking dataset for years bracketing the CIR. Delineating riparian vegetation benefits from using a semi-automated process to present staff with a set of vegetated polygons considered riparian. Staff then review and edit that set to fine tune the polygons using imagery. This process is faster than manual digitizing, and provides more repeatable and consistent results. However it can only be used where good resolution spring CIR imagery is available. An ftp site, managed by the GIS Facility, (ftp.gis.iastate.edu) serves the metadata completed geodatabases of 73 HUC 12 watersheds. Users request access to the data by emailing Calvin Wolter at the Iowa DNR - firstname.lastname@example.org.
This quarter staff compared the baseline inventory 2007-2010 data to recent, 4-band spring 2016 imagery for the five pilot watersheds and updated the database with practice changes. Another goal was to test the efficacy of using color-infrared (CIR) imagery only, without detailed elevation data, to detect new or changed practices. The CIR imagery worked well, even for terraces and water and sediment control basins, since any additions had a bright grass signature and conversely, removals showed a distinct lack of the bright grass ‘look.’ A summary change table was compiled for the pilot watersheds for six conservation practices and riparian vegetation. Overall, pond dams, stripcropping, terraces and water and sediment control basins showed either no change or very slight increase in number. Contour buffer strips showed an overall decrease in area, however grassed waterways had a dramatic increase in both number and area.
For residue cover, researchers have found that defining crop residue types is not straightforward from the majority land cover in the Ag Conservation Planning Framework field boundary database. The automated imagery processing script developed previously continues to be refined to account for and remove subfield variability in residue cover not indicative of the entire field area such as ponds and waterways. Work also continues on processing previously collected residue cover survey data for improved accuracy and planning for additional residue cover data collection this spring. For cover crops, the year-to-year variability complicates setting a consistent vegetation index threshold across dates, as does the difference in spectral response from fall- and spring-planted cover crops. A multi-image approach using average vegetative indexes at various times shows much better promise, with initial classifications around 70% accuracy.
The team finished digitizing the baseline conservation practices geodatabase in August 2015. Staff attention turned to creation of metadata for the practices in the geodatabase and scripting to speed the attribution in each folder. Staff also reviewed student work in the completed watersheds to ensure this was ready when the update process starts. Comparing the baseline data to 2015 or 2016 imagery and updating the database with practice changes is the next step. Priority will be given to three Middle Cedar HUC 12 watersheds with subsequent updates done for the other 37 as time and useful imagery permits, with a completion target of late spring 2016. Evaluation of the baseline practice geodatabase for use in the conservation-planning framework is going on simultaneously with data creation and updating. Discussion has begun for how many Middle Cedar HUC 12 watersheds can be flown for four-band high resolution imagery in spring 2016.
The team has finalized techniques for creating the baseline conservation practice geodatabase using imagery and other GIS data, including aerial photography, satellite imagery, Lidar and high resolution land cover. With ongoing technical assistance from Iowa DNR GIS staff, permanent grassed waterways and vegetated riparian buffers were mapped for 40 Water Quality Initiative (WQI) watersheds. The method for creating a mapping process for permanent vegetation along streams has been refined. Comparing the baseline data to current imagery and updating the database with practice changes will continue this fall. Priority will be given to the three initial WQI watersheds with subsequent updates done for the other 37 as time permits with a completion target of spring 2016.
The team continues to work on techniques for creating a baseline conservation practice database using imagery and other GIS data, including aerial photography, satellite imagery, Lidar and high resolution land cover. With technical assistance from the Iowa Department of Natural Resources, permanent grassed waterways and other structural conservation practices are being mapped for the 40 Water Quality Initiative watersheds. This is a change from the original plan to only map in three selected watersheds. This expansion was necessary because of the varied nature and extent of grassed waterways in different parts of the state.
This project is developing remote sensing protocols for the inventory and monitoring of riparian buffers and grassed waterways. Work is underway to create a baseline conservation practice database from the Iowa Department of Natural Resources (DNR) 2009 high-resolution land cover data. Commercial high-resolution satellite imagery was investigated as a way to improve the database. Discussions are underway with the DNR on possible mapping of permanent structural conservation practices in targeted watersheds.
This project will develop remote sensing protocols for the inventory and monitoring of two permanent vegetative conservation practices — riparian buffers and grassed waterways. To create the baseline conservation practice database, geographic information systems (GIS) staff used Iowa Department of Natural Resources high-resolution land cover data to identify the base conditions for permanent vegetation. To update the conservation practice database, county GIS programs were surveyed and commercial high-resolution satellite imagery investigated. The Middle Cedar watershed was chosen as one target area for this project.