Coastal Services Center

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Dredge Material Siting

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Massachusetts is undergoing a major harbor revitalization effort that requires dredging for deepening and/or widening navigation channels. Coastal managers needed access to environmental and regulatory data to select sites for disposal of the resulting dredged material. A critical piece of information is the location of submerged aquatic vegetation (SAV). SAV data were developed from aerial photography and used with additional data to help create an environmentally sound dredge material disposal plan.

The Project: Massachusetts Harbor Revitalization Plan

Determining where to put dredge material was once a major challenge for the state of Massachusetts. The state needed to consider a variety of environmental concerns, including locations of fisheries and state-protected.

SAV, as well as legal restrictions, such as the location of protected areas. The Massachusetts Coastal Zone Management Program (CZMP) and Science Applications International Corporation (SAIC) developed a geographic information system (GIS) decision-support tool for use with ESRI^® ArcView^® software that contains all the necessary information, data, and criteria to select suitable disposal sites.

Developing SAV Data

SAV data were developed from high-resolution aerial photography at a scale of 1:20,000. The aerial photographs were acquired following a strict set of guidelines to ensure that environmental conditions were optimal for mapping the submerged eelgrass. SAV was delineated from the photographs and the resulting polygon data were easily integrated into the state's GIS decision-support tool. Specific information about benthic mapping methodologies and aerial photography acquisition for benthic mapping can be found in the Center's guidance document, Benthic Habitat Mapping: An Aerial Photographic Approach.

Using SAV Data in the GIS Decision-Support Tool

While state law does not explicitly prevent development in SAV beds, it calls for the protection of existing SAV beds and a 38.5-meter buffer around each bed and locations where SAV used to grow. Areas that are legally restricted from dredge material disposal, such as those within the boundaries of the National Estuarine Research Reserve, were excluded from consideration. Managers used the GIS decision-support tool to evaluate SAV data with a variety of environmental parameters, such as the locations of public fishing grounds and shellfish beds, to select possible disposal sites that would have a minimal impact on the coastal environment.

The Result

With this GIS decision-support tool and accurate, precise SAV data, managers are selecting disposal sites based on a variety of environmental parameters. Because the information is organized in a GIS and the tool is easy to use, citizens and decision makers can visually compare potential sites. By understanding how the different resources relate to one another, users can determine why one site may be preferable to another. Bringing citizens into the process enables them to actively participate in the management and protection of their coastal resources.

An example of how spatial data can be used to make decisions about dredge disposal sites. The red indicates proposed disposal sites and the green indicates SAV beds.

For More information

• Massachusetts Geographic Information System Web site
• Submerged Aquatic Vegetation: Data Development and Applied Uses CD-ROM

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