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Virginia CZM Program: 2017 Coastal Grant Project Description and Final Summary

Project Task:VA CZM logo



Virginia Institute of Marine Science

Project Title:

2017 Submerged Aquatic Vegetation Distribution and Abundance Survey

Project Description:

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 2017, 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 digital aerail imagery acquired during late spring to late summer.

Digital 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 digital aerial imagery 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 2017 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, as well as any ground truth information submitted to VIMS.  The report will be published on the VIMS web site, as in past years.  SAV polygons will also be available on the VIMS SAV interactive web site.

Federal Funding:


Project Contact:

Robert Orth, 804.684.7392;

Project Status:

10/1/17 - 12/31/18; Project Completed

Final Product:

Final Project Summary serves as Final Product.

Project Summary:

The 2017 distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay and its tributaries was mapped from multispectral digital imagery. These were acquired between May and November 2017, with a resolution of 24 cm, encompassing 189 flight lines. National Agricultural Imagery Program (NAIP) imagery was used to augment the multispectral imagery in a portion of the Choptank and Potomac Rivers, as well as Bloodsworth Island and Eastern Bay.
For 2017, 42,448 hectares (104,893 acres) of SAV were mapped in Chesapeake Bay and its tributaries. 
Although the Chesapeake Bay and its tributaries were fully mapped for 2017, weather conditions and security restrictions in the DC area, over Patuxent Air Base and associated mid-Bay areas prevented acquisition of useable imagery in 2016 for a portion of the tidal fresh and mesohaline Potomac River, including Piscataway Creek and St. Mary’s River, preventing those regions from being fully mapped for 2016. In order to ensure a valid analysis of change in SAV distribution and abundance with 2016, all direct comparisons to previous years in this report are restricted to only those regions that were mapped in both years. If a region was not mapped in 2016, comparisons are given using area totals from 2015 instead. The area that was not fully mapped in 2016 supported 822 ha of SAV in 2017 (2031 acres, 2% of the 2017 Bay total). 
Notable changes in SAV distribution were measured between 2017 and 2016. SAV increased 5% from 39,512 ha (97,638 ac) to 41,616 ha (102,837 ac) in the regions mapped for both years. 
In the Tidal Fresh Bay Zone (19 CBP segments), 8,054 hectares (19,903 ac) of SAV were mapped for 2017. However, portions of the zone, including the portion of the Potomac River from Broad Creek to Pomoney Creek, those creeks, and Piscataway Creek, representing 529 ha of SAV in 2017 (1,307 ac, 7% of the zone total) were not mapped for 2016. Comparing the same mapped regions between 2016 and 2017, SAV increased 7% from 7,039 hectares (17,393 ac) in 2016 to 7,516 hectares (18,572 ac) in 2017. In the Oligohaline Bay Zone (25 CBP segments), SAV decreased 2% from 3,475 hectares (8,588 ac) in 2016 to 3,395 hectares (8,389 ac) in 2017. In the Mesohaline Bay Salinity Zone (41 CBP segments), 24,827 hectares (61,350 ac) of SAV were mapped for 2017. However, portions of the zone, including the north shore of the Potomac River from Herring Creek to Smith Creek, those creeks, and the St. Marys River, representing 293 ha of SAV in 2017 (724 ac, 1% of the zone total) were not mapped for 2016. Comparing the same mapped regions between 2016 and 2017, SAV increased 6% from 23,142 hectares (57,185 ac) in 2016 to 24,534 hectares (60,626 ac) in 2017. In the Polyhaline Bay Zone (8 CBP segments), SAV increased 5% from 5,856 ha (14,471 ac) in 2016 to 6,172 ha (15,251 ac) in 2017. For 2017, 6,570 hectares (16,234 ac) were mapped in the Delmarva Peninsula Coastal Bays Zone (Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and Southern Virginia coastal bays). Conditions in 2016 prevented us from mapping the Delmarva Peninsula coastal bays. Therefore all comparisons are made to 2015, the most recent year that this area was fully mapped. In the Delmarva Coastal Bays Zone (10 CBP segments), SAV increased 9% from 6,039 ha (14,924 ac) in 2015 to 6,570 ha (16,234 ac) in 2017.
The 2017 SAV report can now 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

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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