W&M ScholarWorks Reports Winter 1-1-2001 Riparian Forest Buffer Restoration Targeting for the Rappahannock River Watershed Anne Newsome Virginia Institute of Marine Science Carl Hershner Virginia Institute of Marine Science Dan Schatt Virginia Institute of Marine Science Virginia Institute of Marine Science, Wetlands Program Follow this and additional works at: https://scholarworks.wm.edu/reports Part of the Natural Resources and Conservation Commons Recommended Citation Newsome, A., Hershner, C., Schatt, D., & Virginia Institute of Marine Science, Wetlands Program. (2001) Riparian Forest Buffer Restoration Targeting for the Rappahannock River Watershed. Wetlands Program Technical Report no. 01-2. Virginia Institute of Marine Science, College of William and Mary. http://dx.doi.org/doi:10.21220/m2-94zr-hf69 This Report is brought to you for free and open access by W&M ScholarWorks. It has been accepted for inclusion in Reports by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Riparian Forest Buffer Restoration Targeting for the Rappahannock River Watershed By Anne Newsom, Carl Hershner and Dan Schatt Introduction A little over three hundred years ago, more than ficulty in designing a protocol based on environ- ninety-five percent of the land within the Chesa- mental evaluation is that there is no well-defined peake Bay watershed was forested; today’s esti- paradigm for evaluation of potential environmen- mate of forest cover is just over sixty percent tal benefits associated with reforestation of ri- (Forested Lands, 1997). Much of this defores- parian areas. Guidance must be developed by tation has occurred in the riparian zone, an area inference from a variety of extant studies on per- of high ecological importance. The Chesapeake formance of specific functions by riparian for- Bay Program recognizes that “forests along wa- ests. Another constraint on development of a terways, also known as ‘riparian forests,’ are an targeting protocol applicable to large areas is the important resource that protects water quality” availability of data to support the decision rules. (Riparian Forest Buffers, 1996). In addition to After receiving available data sets, it was decided protecting water quality, forests along the shore to limit the targeting protocol to information function to maintain the integrity of the stream about land use/land (LULC) cover adjacent to channel, reduce the impact of upland pollution surface waters. This requires just two data sets: sources and supply food and habitat resources shoreline position and land use/land cover. The to fish and other wildlife (USDA, 1997 and US- consequence of limited data is decision rules EPA, 1996). In recognition of these many poten- must be very simple. Despite these constraints, tial benefits, it has become the official policy of the targeting protocol developed for the the Commonwealth of Virginia, as a partner in Rappahannock River watershed proved capable the Chesapeake Bay Program, to pursue refores- of ranking areas at two different scales. tation of 610 miles of its shorelines by the year 2010. How is Virginia, in cooperation with the Chesapeake Bay Program, going to accomplish Approach this task? The riparian forest buffer restoration project To be effective in increasing water quality and undertaken by VIMS was designed to operate in habitat resources within the Bay watershed, “ri- ERDAS IMAGINE using classified Landsat TM parian buffers need to be planned and imple- data and digital shoreline data. The Landsat mented on a watershed scale” (US-EPA, 1996) TM data gathered from 1991, 1992, and 1993 and also located in areas where buffer function (leaf on coverage) was classified as part of the can be maximized. There are several approaches Multi Resolution Land Cover (MRLC) classifica- for prioritizing riparian zones for restoration ef- tion program. The protocol assumes that the forts. The protocol developed by VIMS is based basic resolution of the Landsat TM imagery de- on an evaluation of environmental benefits pro- fines the detectable riparian zone as a 30 meter vided by riparian forest buffers (RFB). The dif- wide swath. The protocol uses information 1 about the land use/land cover (LULC) within the tribute to nonpoint source pollution; (2) have a 30m riparian zone as well as information about high proportion of riparian lands; and (3) have conditions in the next two 30m zones moving a high proportion of LULC within the riparian inland. The digital shoreline maps were U.S. zone which might contribute to nonpoint source Geologic Survey files developed at a 1:100,000 pollution. In order to determine which HUs con- scale. The hydrologic unit (HU) boundaries are tribute the most to nonpoint source pollution, defined by Virginia’s Department of Conserva- each defined land use class in the MRLC classi- tion and Recreation as 8-digit hydrologic units. fication is assigned to a category of potential pollution contribution. All developed and crop The targeting protocol uses a two phase approach lands are assigned to the class of potentially to designate priority restoration areas. The first polluting land uses, whereas wetlands, forested phase attempts to rank HUs within a watershed lands and barren lands are all considered non- based on their potential pollution contribution polluting land uses. to the watershed. The second phase considers the riparian zone within a hydrologic unit and Each indicator is essentially a percentage. For prioritizes shoreline reaches on the basis of op- example, indicator 1 (proportion of LULC which portunity and need for reforestation. might contribute to nonpoint source pollution) is calculated for each hydrologic unit as the per- Phase one of the protocol is accomplished by centage of all land within the HU which is devel- using three indicators that assess the general oped or agricultural. After the values for a par- opportunity and need for riparian reforestation ticular indicator were calculated for all hydro- within each hydrologic unit. In general, the pro- logic units, they were sorted by score. The one- tocol assumes that the need for reforestation is third with the highest scores were given a nu- relatively higher in hydrologic units which: (1) merical value of “3”. The middle one-third of have a high proportion of LULC which might con- scores were assigned a rating of “2”, and the lowest one-third a rank of “1”. After all three indicators are similarly developed the final Wetlands Program prioritization of all hydrologic units is accom- School of Marine Science plished by simply adding the respective values Virginia Institute of Marine Science for each of the three indicators. The result is a College of William and Mary population of cumulative values ranging from 3 Gloucester Point, Virginia 23062 to 9. Hydrologic units receiving the highest val- (804) 684-7380 ues (cumulative score of “8” or “9”) would be those areas within the watershed which have the Dr. Carl Hershner, Program Director highest proportion of developed or agricultural Dr. Kirk Havens, Editor lands, the highest proportion of land adjacent Published by: VIMS Publication Center to surface waters, and the highest proportion of developed or agricultural riparian lands. The This technical report was funded, in part, by the protocol assumes that these three conditions Virginia Coastal Resources Management Program create the greatest relative potential for nonpoint of the Dept. of Environmental Quality source pollution which might be ameliorated by through Grant #NA97O20181-01 of the RFBs. National Oceanic and Atmospheric Ad- The second phase of the protocol studies the ri- ministration, Office of Ocean and Coastal parian zone within a hydrologic unit. All of the Resources Management, under the shoreline within a HU is assessed on a reach by Coastal Zone Management Act of 1972, as reach basis for both opportunity and need. For amended. the purposes of this protocol, a reach is defined as a length of shoreline with a continuous, simi- The views expressed herein are those of the authors lar land use greater than 1000ft. in length. By and do not necessarily reflect the views of NOAA or impressing a minimum reach length of 1000ft, any of its subagencies or DEQ. an inappropriately detailed assessment of the shoreline is avoided. Since RFBs may be de- Commonwealth’s Declared Policy: “to preserve the wet- sired for water quality functions or for habitat lands and to prevent their despoliation and destruction...” functions, the protocol is designed to evaluate the need for each function separately. This sec- Printed on recycled paper. ond phase of the protocol is based entirely on 2 existing LULC in the 30m riparian zone and in ing. A final cumulative priority ranking is devel- the adjacent 60m wide inland area. oped by simply compositing the two function specific rankings. Opportunity for restoration of the riparian zone is assessed by considering the existing riparian LULC. The protocol assumes that reforestation Results is not equally possible on all nonforested areas. Opportunity within a riparian zone is determined VIMS applied the targeting protocol to the to be high for agricultural lands, moderate for Rappahannock River watershed. Application of barren lands, and low for developed lands, ex- the protocol to this watershed generated the find- isting forests, wetlands, and beaches. ings presented below. Need for reforestation is assessed based on LULC HU Prioritization: There are twenty six hydro- in the inland zones of the 30m riparian area. logic units identified within the Rappahannock The need for RFB water quality functions is as- River watershed. Figure 1 presents the ranking sumed to be high when the adjacent inland area of each HU based on their cumulative scores for is developed or agricultural. It is assumed to be the three prioritization indices. The figure shows moderate for any other adjacent inland LULC. that only two of the HUs rank high for potential The need for RFB habitat functions is assumed nonpoint pollution contribution.