Virginia CZM Program: 2016 Coastal Grant Project Description and Final Summary

Project Task:VA CZM logo

7

Grantee:

Virginia Institute of Marine Science

Project Title:

2016 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 2016, 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.

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 2016 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 (http://web.vims.edu/bio/sav/)

Federal Funding:

$60,000

Project Contact:

Robert Orth, 804.684.7392, jjorth@vims.edu

Project Status:

10/1/16 - 12/31/17; Project Completed

Final Product:

Final Project Summary serves as Final Product

Project Summary:

The 2016 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 2016, with a resolution of 24 cm, encompassing 171 flight lines. National Agricultural Imagery Program (NAIP) imagery was used to augment the multispectral imagery in a portion of the Potomac, James, and Pamunkey rivers; Pungoteague Creek; and Mobjack Bay. Turbid conditions and poor weather conditions in 2016 prevented us from mapping the Delmarva Peninsula Coastal Bays.

For 2016, 39,524 hectares (97,668 acres) of SAV were mapped in Chesapeake Bay and its tributaries. However, weather conditions and security restrictions in the DC area, over Patuxent Air Base and associated mid-Bay areas prevented acquisition of useable imagery for a portion of the tidal fresh and mesohaline Potomac River, including Piscataway Creek and St. Marys River. A small portion of this area was covered by NAIP imagery under conditions that were appropriate for mapping SAV. The area that was not fully mapped in 2016 supported 801.75 ha of SAV in 2015 (1981.20 acres, 2% of the 2015 Bay total).

In order to ensure a valid analysis of change in SAV distribution and abundance given the reduced region mapped in 2016, all direct comparisons to previous years in this report are restricted to only those regions that were mapped in both years. Partial totals for 2015 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 2016 and 2015. SAV increased 8% from 36,556 ha (90,334 ac) to 39,512 ha (97,638 ac) in the regions mapped for both years.

In the Tidal Fresh Bay Zone (19 CBP segments), 7,039 hectares (17,393 ac) of SAV were mapped for 2016. However, portions of the zone, including the portion of the Potomac River from Broad Creek to Pomoney Creek, those creeks, and Piscataway Creek, representing 643 ha of SAV in 2015 (1,588 ac, 9% of the zone total) were not mapped for 2016. Comparing the same mapped regions between 2015 and 2016, SAV increased 9% from 6,430 hectares (15,889 ac) in 2015 to 7,039 hectares (17,393 ac) in 2016. In the Oligohaline Bay Zone (25 CBP segments), SAV decreased 15% from 4,091 hectares (10,109 ac) in 2015 to 3,475 hectares (8,588 ac) in 2015. In the Mesohaline Bay Salinity Zone (41 CBP segments), 23,144 hectares (57,191 ac) of SAV were mapped for 2016. 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 159 ha of SAV in 2015 (393 ac, 1% of the zone total) were not mapped for 2016. Comparing the same mapped regions between 2015 and 2016, SAV increased 20% from 19,290 hectares (47,668 ac) in 2015 to 23,142 hectares (57,185 ac) in 2016. In the Polyhaline Bay Zone (8 CBP segments), SAV decreased 13% from 6,745 ha (16,667 ac) in 2015 to 5,856 ha (14,471 ac) in 2016.

The 2016 SAV report can now be viewed at:

http://web.vims.edu/bio/sav/sav16/index.html and also on VIMS interactive map: http://web.vims.edu/bio/sav/maps.html. 

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: Laura.McKay@deq.virginia.gov

A more detailed Scope of Work for this project is available. Please direct your request for a copy to Virginia.Witmer@deq.virginia.gov or April.Bahen@deq.virginia.gov.

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


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