CICEET Progress Report for the period 9/01/09 Through 2/28/10
Project Title: Vegetation, Impervious Surfaces, Soils, and Topographic Analysis Tools: Geospatial Technology to Promote Coastal Water Quality
Principal Investigator(s): Thomas R. Allen
Project Start Date: September 1, 2007
Report Compiled By: Thomas R. Allen
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A. Objective Description
Collaboration with end-users identified the need to further refine the subwatershed delineation and document successful use case examples for water quality and storm water management. This was pursued by a use case analysis of the Town of Moyock watershed by seeking additional test cases in adjoining regions. Scale of analysis also poses alternatives and constraints, such as parcel- vs subdivision-scale modeling. Currituck County comprises a heterogeneous situation, where fine-scale water quality impacts combine with landscape and sub-regional scales. We sought to determine the efficacy of the newly derived subwatershed units for mapping future impacts on water quality using land use zoning plans. Wider access to the tools will provide ArcGIS modelbuilder scripts and documentation. A case example will also be documented using an ArcGIS Server installation. Detailed documentation, a user guide, and a straightforward, robust output product are also in development. The illustration of the Currituck case studies will provide a public example in a workshop and individual meetings (e.g, NC NERR, Sea Grant, and Currituck Growing Green initiative.)
B. Tasks to Meet Objectives
1. Technical objectives
i. Test the refine the runoff and infiltration models for multiple scale subwatersheds
ii. Assess the sensitivity of the modeling tools to present vs. future land use scenarios, using a ìbuild-outî scenario and reclassification of existing land use to match future land use plans.
iii. Produce graphical and descriptive documentation for external evaluation.
2. Non-technical objectives
i. Maintain and inform participating collaborators on the results using the new subwatershed products.
ii. Obtain and respond to feedback from the use-case scenario for a future land use impacts assessment.
iii. Document the model and find a willing beta-test site.
3. Evaluate alternative modes of delivery using server-based GIS.
C. Progress on Tasks
1. Technical progress
We refined the previously created subwatersheds and produces a complete county-wide map for future land use planning and water quality modeling. The Moyock area was selected in consultation with planners for analysis of potential future land use on water runoff. The model was run for the current land use using a reclassified NOAA Coastal Change Analysis Program (CCAP) 2006 classified image. Future land use was obtained from the county and used to recode current land use classes to future conditions. These conditions were constrained to the parameters in our infiltration and runoff components. The future land use runoff conditions were mapped in model output to compare and contrast against the current condition output. Additional descriptive statistical results are in process for documentation for external evaluation with our collaborators.
Further application of these data could inform not only planning but also regulation and permitting as well as future ordinance development for storm water management.
2. Hurdles in accomplishing tasks
Modelbuilder tools continue to be the mainstay of our methods and have not yet been applied to the GIS server platform. We did obtain at opportunity a higher resolution 10-foot floating point DEM from the NC Floodplain Mapping Program. However, extensive utilization of this resource is prohibitive to desktop and current ArcGIS performance. We have instead, used GRASS GIS for some of the pre-processing, which allows larger raster file sizes and the possibility of nested calculations in a scripted geoprocessing environment.
Our test using future land use plan data required the additional development of a reclassification scheme, so that future land use classes could approximate the existing land cover data in the model. We developed and tested a lookup table for this. The output from these steps requires consultation to ensure the appropriate impacts (e.g., imperviousness) are reflected in the output.
II. Data Generated
Our principal data products include the same as before, subwatershed delineations, model input (soil characteristics, CCAP land cover, DEM and slope derivatives, and soils), and output layers (curve numbers, potential infiltration, and potential runoff.) In addition, this extra period of time has provided us to model FUTURE land use impacts on water quality and runoff. We have now developed additional maps in the Moyock watershed by way of example and rendered the cartography using a common classification scheme for accurate comparison.
III. Project Objectives for Next Reporting Period
The project has documented the current and future land use impacts on water quality in a model that has sufficient resolution at the subwatershed community scale. Further application and demonstration is needed to contextualize and demonstrate to communities the adaptation and environmental benefits afforded by these techniques. We aim to support the use of these and its more widespread, extensive calculation in Currituck County in the final phase of the project. We also seek a partner in an alternative site to adopt the approach. For this, we are engaging with local non-profit foundations working on degraded subwatersheds of the Neuse River and Tar River basins. In addition to ameliorating existing impairments, the potential for potential to also strategically mitigate future degradation is becoming clear. Moreover, the finer resolution afforded by the high quality DEMs and our subwatershed delineation provide a scale that matches the increasingly sought-after refinement for sustainable community design. The next period will report on these developments, document the completed technical development, and provide a series of nacent ìSuccess stories.î