Coastal Services Center

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Nonpoint Source Pollution and Erosion Comparison Tool (N-SPECT)

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N-SPECT is a complex yet user-friendly geographic information system (GIS) extension that helps coastal managers and local decision makers predict potential water-quality impacts from nonpoint source pollution and erosion. Users first enter information about their area (land cover, elevation, precipitation, and soil characteristics) to create the baseline information. They can then add different land cover change scenarios (such as a development) to get information about potential changes in surface water runoff, nonpoint source pollution, and erosion.

Applicability

N-SPECT was initially developed as a decision-support tool for coastal managers in Hawaii and has since been applied in coastal areas around the U.S., the Caribbean, Central America, and the South Pacific. It operates most effectively in medium-to-large watersheds having low-to-moderate topographic relief. Studies have shown that N-SPECT tends to over predict sediment delivery in regions having extreme precipitation regimes and very steep slopes, so users are strongly encouraged to account for these potential sources of error during the course of sediment delivery analyses.

Specifications

N-SPECT is a GIS extension that runs in ESRI’s ArcGIS environment. Versions are currently available for ArcView 8.3, ArcView 9.0, ArcView 9.1, and ArcView 9.2. The ArcGIS Spatial Analyst extension must be installed.

Minimum system requirements for the tool:

• Platform: PC-Intel
• CPU speed: 1.0 GHz recommended or higher
• Processor: Intel Pentium or Intel Xeon processors
• Memory: 512 MB minimum, 1 GB recommended or higher

Required data inputs:

• Land cover grid
• Digital elevation model
• Precipitation grid
• Pollutant coefficients (based on land cover)
• Soil type data

The tool provides decision makers with the following features:

• Accumulated runoff, pollutant, and sediment load grids
• Pollutant concentration grids
• Pollutant assessment grid, which compares the resulting concentrations in receiving waters to user-specified water-quality standards

The ability to simulate land cover changes, such as developments

Common Data Sources

Many of the input data sets required to run the tool are free and available on the Internet. In addition to these nationally based sources, many states and communities also have free data available on-line.

Land cover:

• National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center Land Cover Analysis
• Multi-Resolution Land Characteristics (MRLC) National Land Cover Database 2001
• U.S. Geological Survey (USGS) Land Cover Institute

Topography:

• NOAA Coastal Services Center Topographic Change Mapping
• USGS National Elevation Dataset

Soil:

• U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey Geographic Database

R-Factor (rainfall-runoff erosivity factor):

• USDA NRCS Electronic Field Office Technical Guide (eFOTG)
• USDA NRCS National RUSLE2 Database

Precipitation:

• Oregon Climate Service PRISM Group
• NOAA National Climatic Data Center

Download Instructions

When you download N-SPECT, you will receive the GIS extension, on-line help files, a sample data set, a step-by-step tutorial, a user's manual, and a technical guide.

Consult the tutorial (Adobe Reader is needed to view and print PDF files) for further instruction on how to operate N-SPECT. Note: If a previous version of N-SPECT is already installed, remove it before installing a new version. To uninstall the previous version, access the Add or Remove Programs function in the Control Panel, select N-SPECT, and then click Remove. Follow the instructions from the wizard to uninstall the tool. Check the location where N-SPECT was installed to be sure it is empty (note that the directory will not be deleted).

N-SPECT for ArcView 8.3:
Select the link below and either save the file or run it when prompted.

1. Download the N-SPECT extension for ArcView 8.3.
   Follow the instructions to complete the setup and an "NSPECT" directory will be installed on your C:\ drive.

N-SPECT for ArcView 9.x:
If you are running ArcView 9.x, a patch is available for N-SPECT. This patch is meant to be applied on top of the ArcView 8.3 version of N-SPECT. Be sure to install the ArcView 8.3 version of N-SPECT first. Select the appropriate links below and either save the file or run it when prompted.

1a. Download the N-SPECT extension for ArcView 8.3
Follow the instructions to complete the setup and an "NSPECT" directory will be installed on your C:\ drive.

2a. Download the N-SPECT patch for ArcView 9.0 or 9.1
Follow the instructions to complete the installation and N-SPECT will be updated for ArcView 9.0 or 9.1.

2b. Download the N-SPECT extension for ArcView 9.2
Follow the instructions to complete the installation and N-SPECT will be updated for ArcView 9.2.
A PDF listing known issues is included in the download.

If you have difficulty accessing this file or if you need more information, you may contact the NOAA Coastal Services Center.

Publications

Tool Documentation:

• User's Guide (PDF, 3.10MB)
• Technical Guide (PDF, 953KB)
• Advanced Applications (PDF, 10.4MB)
• Tutorial (PDF, 3.31MB)
• *Guidance for Preprocessing SSURGO Data (PDF, 86 KB)
• *Guidance for Preprocessing PRISM Data (PDF, 401 KB)

  *Note: these documents are not included in the Help directory after installing N-SPECT.

Presentations:

• Introduction to N-SPECT (PDF, 1.36MB) - A NOAA CSC presentation covering the tool description, data needs and applicability. Updated in 2006.
• Linking Land Cover to Water Quality (PDF, 4.06MB) - A NOAA CSC presentation describing an application in the Weeks Bay watershed, Alabama. Presented at the 2006 Urban and Regional Information Systems Association (URISA) conference in Vancouver, Canada.
• Integrating N-SPECT with the development of a management plan for the Kingston Lake Watershed (PDF, 6.64 MB) – Researchers at Coastal Carolina University demonstrate an application of N-SPECT to model predicted impacts of increased population growth on pollutant loads in Kingston Lake watershed. Presented at the 2007 GeoTools conference in Myrtle Beach, SC.

Posters:

• N-SPECT Overview (PDF, 26.5MB) - A poster developed by NOAA CSC that covers the technical aspects of the tool including data inputs, outputs, and scenario analyses. Presented at the 2005 Coastal Zone conference in New Orleans, LA.
• Tools for Assessing Impacts on Water Quality (PDF, 13MB) - A NOAA CSC poster that presents the results of the applications of the Impervious Surface Analysis Tool (ISAT) and N-SPECT in Horry County, SC using two eras of land cover data. Presented at the 2005 MultiTemp conference in Biloxi, MS.
• Calibration and Validation of N-SPECT for Hanalei Watershed (TIF, 17.4MB) – A poster developed by University of Hawaii Natural Resources and Environmental Management researchers for the 2006 American Geophysical Union (AGU) conference in San Francisco, CA.

Known Issues

For a list of known issues and their fixes, please consult the following document: KnownIssues.pdf

Note: Viewing the PDF files on this page requires the use of a plug-in such as the Adobe^® Reader^®. If you do not have such a plug-in already installed, you may download Adobe Reader by selecting the "Get Adobe Reader" button below.

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