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Center for Spatial Information and Research

Develop & Test Geospatial Technologies & Methods for Cumulative Impact Assessment for Shoreline Management



In Washington State, as in most states throughout the nation, the chief causes of shoreline degradation are the cumulative impacts of land use alterations and nonpoint source pollution throughout contributing watersheds. Washington's Coastal Zone Management Program is implemented primarily through locally adopted plans and regulations approved by the state. These plans can address the cumulative effects of growth if planners are equipped with scientifically based assessments indicating the most beneficial location, type and extent of preservation, restoration and enhancement activities. This objective provides information onhow to scope, identify appropriate geospatial methods, and provide the necessary documentation required in developing defensible cumulative impact analyses and restoration plans. We developed a systematic process for quantitatively and qualitatively reviewing predicted cumulative effects and alternative actions described in Washington Shoreline Master Programs, Environmental Impact Statements and Environmental Assessments, based on the various policy definitions of cumulative impacts and minimum compliance measures associated with developing Shoreline Master Programs, Environmental Impact Statements, and alternatives analyses for full NEPA disclosure. Agency publications were reviewed to provide a background of the regulatory intent for each analytical requirement. Case examples were developed to demonstrate how to scope projects for determining the most appropriate geospatial methods to apply, how to estimate the magnitude of impact to specific resources, and how to accessibly present analysis findings.

The approach developed guidance documents accessible via a web interface that:

  • describe the use and limitations of currently available and relevant geospatial data, information and cumulative impact assessment methods
  • explain how to interpret and use existing geospatial information effectively
  • offer illustrated case examples of cumulative impact assessments in a shoreline context

Available applicable geospatial data was compiled, data sources documented and made accessible on line. An approach for analyzing cumulative effects is presented through stream (McLane Creek, Thurston County ), lake ( Moses Lake , Grant County ) and marine shoreline (Jackson Beach, San Juan County ) case study examples.

Each case study required that the following steps be tailored according to data availability, local demographics and the specific long range planning goals of the jurisdiction.

Set Context

  1. 1. Describe geographic boundaries & scope of analysis
  2. 2. Characterize regional landscape influencing project area
  3. 3. Describe what actions/projects will be assessed in the analysis
  4. 4. Identify timeframe for analysis & affected resources

Perform Analysis

  1. 1. Create matrix (or systems diagram) linking each activity to affected resources.
  2. 2. Provide a geospatial analysis of baseline conditions
  3. 3. Complete scenario modeling or apply predictions based on trend analysis under different zoning and regulatory regimes.

The scenario modeling required development of innovative geospatial predictor tools. These were developed for use in ESRI ArcGIS but can be ported to any GIS system. The geospatial predictor tools were presented along with the overall approach and case study analyses at the Puget Sound/Georgia Basin Research Conference. This provided an opportunity for feedback from regional, national and international scientists as well as a means to introduce RGIS-PN to the broad audience of nearshore, riparian and coastal land use and natural resource managers. The guidance is available for viewing and download through the RGIS-PN website. 

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