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Virginia CZM Program: 2011 Coastal Grant Project Description and Final Summary

Project Task:VA CZM logo



Virginia Institute of Marine Science

Project Title:

2011 Submerged Aquatic Vegetation Distribution and Abundance Survey of Virginia’s Chesapeake Bay and its Tributaries

Project Description as Proposed:

Submerged aquatic vegetation (SAV) is a critical living resource in Chesapeake Bay that has undergone rapid and dramatic baywide fluctuations in distribution and abundance over the last two decades, and is being subjected to declines in water quality and to ever increasing pressure from recreational, commercial, and industrial demands. Because SAV is dependent on good water quality to which it responds over short time scales, it can be an important indicator of water quality. In 2011, VIMS will continue the annual SAV survey program, begun in 1984, by mapping SAV in the shoal areas of the entire Chesapeake Bay and its tributaries from aerial photography acquired during late spring to late summer. Black & white aerial photography will be acquired at a photographic scale of approximate 1:24,000, following guidelines that address tidal stage, plant growth, sun angle, turbidity, wind, atmospheric transparency, sensor operation and land features to allow for acquisition of photographs under near optimal conditions.  Ground data on species distribution and abundance will be collected by participating agencies and citizen groups from as many of the Chesapeake Bay Program segments as possible and included in the final report. The aerial photographs will be evaluated for SAV signatures using all available information. Photographs containing SAV signatures will be orthographically corrected and mosaiced by USGS 7.5 minute topographic quadrangles using Orthobase and Imagine image processing software . The perimeters of all SAV beds mapped from the 2011 aerial photography will be delineated on-screen using ArcInfo geographic information system (GIS) software and stored in an ArcInfo GIS database. A final report will include maps of all SAV beds, and areas of these beds. The report will be published on the VIMS web site, as on past years.

Federal Funding:


Project Contact:

Robert J. Orth, 804.684.7392;

Project Status:

10/1/2011 - 12/31/2012; Project Completed

Final Product Received:

Final Project Summary serves as Final Product.

Project Summary Provided by Grantee:

The 2011 distribution of submerged aquatic vegetation (SAV) in the Chesapeake Bay and its tributaries was mapped from black and white aerial photographs. These were taken between May and December 2011, at a scale of 1:24,000, encompassing 160 flight lines. For 2011, 23,457 hectares (57,964 acres) of SAV were mapped in the Chesapeake Bay and its tributaries. However, while the entire Bay was flown, some portions of the Bay were not mapped since SAV signatures were masked by excess turbidity present months after the passage of Hurricane Irene and Tropical Storm Lee. The regions that were not mapped are contained within nine CBP segments, including the Middle, Upper and Western Branch of the Patuxent River; the Middle and Upper Potomac River; Piscataway Creek; and the Anacostia River. These regions had 2,183 ha of SAV in 2010 (5,393 ac, 7% of the 2010 total). In order to ensure a valid analysis of change in SAV distribution and abundance given the reduced region mapped in 2011, all direct comparisons to previous years in this report are restricted to only those regions that were mapped in both years. Partial totals for 2010 have been computed for CBP segments, Bay zones, and the entire Bay using only those regions mapped for both years.

Notable changes in SAV distribution were measured between 2010 and 2011. SAV decreased 22% from 30,056 ha (74,271 ac) to 23,346 ha (57,690 ac) in the regions mapped for both years. SAV decreased in all three (Upper, Middle, and Lower) geographic zones delineated for the Chesapeake Bay. In 2011, SAV increased in 26, decreased in 34, and remained unvegetated in 33 of the 93 CBP segments.

In the Upper Bay Zone (21 CBP segments extending south from the Susquehanna River to the Chester and Magothy rivers), SAV decreased 38% from 8,641 ha (21,353 ac) in 2010 to 5,377 ha (13,287 ac) in 2011. In the Middle Bay Zone (44 CBP segments extending south from the Bay Bridge to the Rappahannock River and Pocomoke Sound, and including the Potomac River), 11,745 hectares (29,023 ac) of SAV were mapped for 2011. However, portions of the zone, including the Middle, Upper and Western Branch of the Patuxent River; the Middle and Upper Potomac; Piscataway Creek; and the Anacostia River, representing 2,183 ha of SAV in 2010 (5,393 ac, 15% of the zone total) were not mapped for 2011. Comparing the same mapped regions between 2010 and 2011, SAV decreased 4% from 12,162 hectares (30,053 ac) in 2010 to 11,634 hectares (28,749 ac) in 2011. In the Lower Bay Zone (28 CBP segments covering the region south from the Rappahannock River and Pocomoke Sound regions to the mouth of the Bay), SAV decreased 32% from 9,253 ha (22,865 ac) in 2010 to 6,335 ha (15,654 ac) in 2011. In the Delmarva Peninsula Coastal Bays Zone (Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and Southern Virginia coastal bays), SAV decreased 26% from 7,326 ha (18,102 ac) in 2010 to 5,445 ha (13,455 ac) in 2011.  However SAV did continue to increase in the Southern Virginia coastal bays. The 2011 results can be viewed at : .

Disclaimer: This project summary provides the federal dollars initially awarded to the grantee. Due to underexpenditure or reprogramming of grant funds, this figure may change. For more information on the allocation of coastal grant funds, please contact Laura McKay, Virginia Coastal Program Manager, at 804.698.4323 or email:

A more detailed Scope of Work for this project is available. Please direct your request for a copy to

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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000

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