TARGETING WATERSHEDS FOR RESTORATION ACTIVITIES IN THE CHESAPEAKE BAY WATERSHED Technical Documentation October 4, 2002
Acknowledgements and Disclaimer This project was funded by the Chesapeake Bay Foundation, USDA Forest Service, and Ducks Unlimited, Inc. Cooperators in the analysis and data collection for this project include: Chesapeake Bay Program, Maryland Department of Natural Resources, US Environmental Protection Agency Region 3, Delaware Department of Natural Resource and Environmental Control, Pennsylvania State University, New York State Department of Environmental Conservation, Virginia Department of Forestry, and USGS Water Resource Division. The information contained in this report and accompanying maps are unsuited for, and shall not be used for any regulatory purpose of action, nor shall the report or accompanying maps be the basis for any determination relating to impact assessment or mitigation. The maps and analysis in this report were developed for wetland and riparian restoration planning purposes. Extreme caution should be taken when using this analysis or maps for any other purpose. This report was prepared by Ducks Unlimited, Inc. For additional information about the project, report, or maps, please contact Ducks Unlimited, Inc., Great Lakes/Atlantic Regional Office, 331 Metty Drive, Suite 4, Ann Arbor, MI 48103, (734) 623-2000. - 2 -
Table of Contents Acknowledgements and Disclaimer... 2 Introduction... 4 Watershed Targeting Analysis... 5 DATA... 5 ANALYSIS... 6 Potential Wetland Restoration... 6 Potential Riparian Restoration... 7 Water Quality Analysis... 9 Watershed Ranking for Conservation... 10 Conclusion... 10 Appendix A... 11 Appendix B... 12 Appendix C... 13 Appendix D... 14 Appendix E... 15 Appendix F... 16-3 -
Introduction At the turn of the century, the Chesapeake Bay was considered one of the most productive estuaries in the world, with abundant fish, shellfish, and waterfowl populations. Unfortunately, over the last 40 years wildlife populations of the Chesapeake Bay have declined due to a loss of habitat from development pressures and poor water quality. Because of its importance and the dramatic declines in wildlife populations, the Chesapeake Bay has been identified as a priority area for wetland protection and restoration by the Atlantic Coast Joint Venture of the North American Waterfowl Management Plan, a National Conservation Priority Area by the U.S. Department of Agriculture, and a RAMSAR site by the Convention on Wetlands of International Importance. Since 1997, Ducks Unlimited, Inc (DU) has been working in partnership with the Chesapeake Bay Foundation (CBF) to restore and protect wetland, riparian, and upland habitats on both private and public lands throughout the Chesapeake Bay watershed. These efforts, as well as those of other organizations, are currently opportunistic. Sites selected for restoration are not always integrated into the landscape as a whole, which produces high quality projects with little connectivity and therefore potentially little impact at the watershed level. Conservation in the Chesapeake Bay watershed should be delivered proactively to affect the overall health of the ecosystem by synergistically building wetland-riparian-upland complexes and identifying the most efficient areas on a landscape level in which to target restoration. In order to address the shortcomings of delivering conservation projects in the Chesapeake Bay watershed, DU and CBF teamed up with the USDA Forest Service to form the Chesapeake Bay Conservation Planning Network. The goals of the Network were to: 1) developing a system for targeting conservation efforts and developing restoration programs that is user friendly and accessible to field staff, 2) predict the effects of conservation efforts on water quality, 3) facilitating the development, access, and exchange of spatial data and analysis tools within the Chesapeake Bay Watershed The first goal, developing a system for targeting conservation efforts and developing restoration programs, has three modules: watershed targeting, restoration targeting, and restoration information. This report describes the technical aspects of the watershed targeting phase. For more information about the Chesapeake Bay Conservation Planning Network, please see the Strategic Plan (email Robb Macleod for a copy [rmacleod@ducks.org]). - 4 -
Watershed Targeting Analysis The watershed targeting module ranked the 11 digit watersheds (HUC 11) based on water quality, potential for wetland restoration, and potential for riparian restoration. Water quality data from USGS s SPARROW model was used to rank the 11 digit watersheds for restoration potential due to nitrogen and phosphorus yields from agricultural land use. The Nitrogen and Phosphorus ranks were then combined into the final water quality rank for restoration potential. The wetland restoration potential ranking was derived using the STATSGO soils data and agricultural areas as defined by the USGS s Multi-resolution Land Characterization (MRLC) data. Any hydric soil in the STATSGO layer that was being used as agriculture in the MRLC data was defined as a potential wetland restoration. The wetland potential was then ranked according to 11 digit watershed. The riparian restoration potential ranking was derived by intersecting un-buffered streams from the Chesapeake Bay Program s riparian buffer analysis with agricultural lands in the MRLC data. The length of un-buffered streams in agricultural areas was then divided by the total length of streams in each 11 digit watershed and ranked accordingly. These final three layers (water quality, potential wetland restoration ranking, and potential riparian restoration ranking) were added together to get the final watershed restoration ranking. (See analysis section for more detail) DATA All of the analysis was summarized by 11-digit Hydrologic Unit Code (HUC 11) (also known as watersheds). This dataset was obtained from the Chesapeake Bay Program. Upon inspection of the HUC 11 coverage, there were some missing HUC 11 attributes in Maryland. These HUC 11 attributes were needed because the tabular attributes in the analysis had to be linked back to the HUC 11 coverage. The 14-digit Hydrologic Unit data from Maryland Department of Natural Resources (DNR) has 14 digit, 11-digit, and 8-digit attributes and was used to populate the missing HUC 11 attributes from the Chesapeake Bay Program s 11 digit HUC in Maryland. While accomplishing this task, some of the HUC 11 boundaries did not match between the data set from the Chesapeake Bay Program and the Maryland DNR. In order to remain consistent with Maryland DNR s HUC 11 attributes, the boundaries from the Maryland DNR were used when problems were encountered. In some cases, multiple polygons were merged to create new ones, and in others, portions clipped off and merged with adjacent ones to match. The resulting modified HUC 11 data set was used for the analysis. The five main data layers used in this analysis were: USDA s STATSGO soils, USGS s Multiresolution Land Characterization (MRLC), Chesapeake Bay Program s riparian buffer analysis, and USGS s SPARROW model for the water quality data. The tables below lists the data layers that were used in each of the three analysis phases. - 5 -
Potential Wetland Restoration Description Scale Source Date Hydric Soils 1:250,000 STATSGO, USDA December, 1994 Agricultural Lands 30 meter MRLC, USGS 1997 Potential Riparian Restoration Description Scale Source Date Agricultural Lands 30 meter MRLC, USGS 1997 Riparian Forest Buffer varies Chesapeake Bay Program 1997 Water Quality Description Scale Source Date Agricultural Lands 30 meter MRLC, USGS 1997 Nutrient Loadings SPARROW v.2, USGS 2001 ANALYSIS Potential Wetland Restoration The first step in determining areas with potential for wetland restoration was to determine the location of hydric soils. The definition of a hydric soil is a soil that formed under conditions of saturation, flooding or ponding long enough during the growing season to develop anaerobic conditions in the upper part. Hydric soils are most suited for delivering wetland restorations. Currently, the only watershed wide soils coverage available to delineate hydric soils is USGS s STATSGO dataset. In STATSGO, each map unit can have multiple components and each component can have multiple layers. Hydric soils in STATSGO is identified by Hydric = Y or Hydric = N. Hydric = Y means that the map component does have hydric soil, while hydric = N means that the map component does not have hydric soil. For each map unit the percentage of Hydric = Y was calculated using all components. The result was an attribute for each soil type that gave the percentage of the map unit that was hydric (hydric = Y ). Through a series of interactive analysis, it was decided that all those areas having hydric soils above 4% would be used in the analysis as a hydric soil. The second step was to identify the agricultural lands in the watershed. Most conservation programs that deliver wetland restorations require a history of farming. Agricultural lands from USGS s Multi-resolution Land Characterization (MRLC) were selected. Agricultural lands in MRLC are the planted/cultivated areas defined as areas characterized by herbaceous vegetation that has been planted or is intensively managed for the production of food, feed, or fiber; or is - 6 -
maintained in developed settings for specific purposes (Appendix B). This data was originally in a raster format, which was converted in a vector format to be used in the analysis. The third step was to intersect the hydric soils and agricultural lands to find areas of hydric soils that are contained within agricultural lands. This combination was then intersected by HUC 11 to calculate the area of hydric-agricultural by each HUC 11. The hydric-agricultural area was then standardized within each HUC 11 by dividing by the total area of the HUC 11 unit. The standardized hydric-agricultural areas were then ranked on a scale of 1-10 based on quantiles (Appendix C). STATSGO Soils Source: NRCS Hydric Soils (Greater than 4%) in Agricultural Areas Hydric Soils (Greater then 4%) in Agricultural Areas by HUC 11 Summarize Area by HUC 11 Agricultural Land Source: MRLC 97 Hydrological Units, 11 Digit Source: Chesapeake Bay Program (modified) Proportion of Hydric Soils in Agricultural areas Potential Riparian Restoration The first step in determining areas with potential for riparian restoration was to identify all unbuffered streams. The riparian forest buffer analysis from the Chesapeake Bay Program was used to make this determination. This data set was compiled from a number of sources, including: USGS Digital Line Graph (DLG) 1:100,000 scale hydrography Pennsylvania Department of Transportation 1:24,000 scale hydrography Maryland Office of Planning 1:24,000 scale hydrography USDA Natural Resource Conservation Service 1:24,000 & 1:100,000 scale hydrography USGS 8-digit hydrologic units EPA EMAP Level 2 Land Cover 25m cell resolution The riparian forest buffer analysis was generated using an algorithm created by Pennsylvania State University. The following attributes were used in the analysis: L300 (=1, buffered 300+ on left =0, not buffered 300+ on left) R300 (=1, buffered 300+ on left =0, not buffered 300+ on left) L100 (=1, buffered 100+ on left =0, not buffered 100+ on left) R100 (=1, buffered 100+ on left =0, not buffered 100+ on left) For the potential riparian restoration analysis, un-buffered streams were selected based on those streams in the riparian forest buffer analysis that did not have a buffer on either side. In other words, if all 4 attributes had zero values (no buffer) then it was extracted into a new coverage of un-buffered streams. - 7 -
The second step was to identify the agricultural lands in the watershed, as most conservation programs that deliver riparian restorations require a history of farming. The MRLC land cover data was used to determine the agricultural lands as described in the potential wetland restoration section. The third step was to intersected the un-buffered streams with agricultural lands to identify those un-buffered stream segments that are in agricultural areas. These un-buffered riparian stream segments in agricultural areas were then summarized using the HUC 11 value and the length attribute, to produce a table showing the total length of un-buffered riparian stream segments in agricultural areas within each HUC 11. The fourth step was to summarize the total length of all streams within each HUC 11. This was done by intersected all streams in the riparian forest buffer analysis with the modified HUC 11 data layer. A summary was done using the HUC 11 attribute that summed the length attribute. This summary created a table with HUC11 values and corresponding total length of stream segments in each HUC 11. The final step was to divided the total length of un-buffered riparian stream segments in agricultural areas by the total length of all stream segment within each HUC11 to standardize the values. The resulting value represented the proportion of stream segments in each watershed that was unbuffered in agricultural areas. These values were ranked according to quantiles 1 through 10 (Appendix D). Riparian Stream Segments Source: Chesapeake Bay Program Hydrological Units, 11 Digit Source: Chesapeake Bay Program (modified) Riparian Streams with HUC11 attribute Extract Non-buffered Agricultural Lands Source: MRLC 97 Non-buffered segments in Agriculture Summarize Total Length by HUC 11 attribute Summarize Total Length by HUC 11 attribute Proportion of stream segments non-buffered and in agricultural areas - 8 -
Water Quality Analysis There are at least four water quality models available to use to rank the Chesapeake Bay watershed. The NRCS has ranked the 8 digit watershed in a study titled Potential Priority Watershed for Protection of Water Quality from Nonpoint Sources Related to Agriculture. The EPA has ranked the 8 digit watersheds with their Index of Watershed Indicators program. The Chesapeake Bay Program has water quality data and models available for the Chesapeake Bay watershed at the 8 digit level. The USGS has develop their SPARROW model for water quality in the Chesapeake Bay watershed both at the 8 digit and 11 digit level. Since this study was being done at the 11 digit level, the only data available at this scale was the USGS s SPARROW model. Nutrient estimates predicted by SPARROW are by stream reach for incremental yields and for total yields delivered to the Bay. The incremental yields of nitrogen and phosphorus were used in the analysis. As defined, Incremental Yield is the amount (load per area) of total nitrogen/phosphorus that is generated locally (independent of upstream load) and contributed to downstream end of each stream reach. Each stream reach and associated watershed is treated as an independent unit, quantifying the amount of nutrient generated. The SPARROW model uses a segmented-watershed network which is based on stream reaches and their associated watershed boundaries. The segmented watershed network does not match the HUC 11 one to one. In order to transfer the nutrient information from the SPARROW models segmented watershed network to the HUC 11, the incremental yield had to be converted into a load and recalculated based on the HUC 11. This calculation was done by first intersecting the segmented watershed network with the HUC 11 to create a new coverage (Intersected). The loads (yield time the area of the segmented watershed network) from the SPARROW model was then assigned to each of the polygons in the Intersected coverage. The Intersected layer was then dissolved by HUC 11 and a sum of the load for each portion in the HUC 11 was calculated and divided by the area of the HUC 11 watershed. This new value corresponds to the SPARROW yield by HUC 11. This estimate assumes that the yield was equal across a segment, and thus the load of a small portion was equal to it s area times the yield. Summing these loads properly weights larger polygons against smaller ones. These values were ranked 1 through 10 for both phosphorus and nitrogen yield, and then these ranks were averaged to get the water quality ranking (Appendix E). Water Quality Data by Segment Source: Sparrow Version 2 Hydrological Units, 11 Digit Source: Chesapeake Bay Program (modified) Water Quality Data by HUC 11 Incremental Yield due to Agriculture * Area of Polygon = Load Incremental Yield due to Agriculture adjusted to HUC 11 Dissolve by HUC11, Sum Load Divide Summarized Yield by watershed Area = New Yield - 9 -
Watershed Ranking for Conservation To derive a final watershed ranking for conservation practices, the ranking for potential wetland restoration, potential riparian restoration and water quality risk factors were combined and averaged by dividing by 3 (Appendix F). Total Rank = (Potential Wetland Areas + Potential Riparian Areas + Water Quality Risks) / 3 Values were rounded to the nearest integer. Conclusion This analysis is still in draft form, and needs to be reviewed by field staff and cooperators. Any comments or suggestions on this analysis are welcome. A few of the ideas for future investigations are as follows: Calculate riparian buffer for both sides of the streams instead of looking at only those streams that have no buffers. Update riparian forest buffer analysis (Penn State University is currently working on an update). Generate a soil moisture index to be used as a more detailed hydric layer for the potential wetlands analysis. Rank potential wetland areas and potential riparian areas independently with water quality. Determine different ranking schemes (rather then averaging the three layers) The next step is to locate areas within those high potential 11 digit watersheds that would be suitable for restoration efforts. These potential restoration sites will be analyzed based on a number of factors; including, the potential riparian and wetland areas produced in the landscape level targeting analysis, distance to protected areas, proximity to existing wetlands, and distance to riparian features. The result will be a map of restoration hot spots. The final step will be to produce an Internet map viewer and analysis tool for conservation managers and field staff delivering restoration projects. Without this kind of information, a lot of the funds spend on nonpoint source restorations may not have the desired effect on the coastal estuaries of the Chesapeake Bay. - 10 -
Appendix A PROCESS FOR IDENTIFYING PRIORITY AREAS FOR RESTORATION TARGETING STATSGO Soils Riparian Stream Segments Water Quality Data by Segment Agricultural Land Hydrological Units, 11 Digit Hydrological Units, 11 Digit Hydrological Units, 11 Digit Riparian Streams with HUC11 attribute Water Quality Data by HUC 11 Hydric Soils (4% and greater) in Agricultural Areas by HUC 11 Select out non-buffered segments Incremental Yield due to Agriculture * Area of Polygon = Load Summarize Area by HUC 11 Agricultural Lands Dissolve by HUC11, Sum Load Proportion of Hydric Soils in Agricultural areas RANK 1-10 Non-buffered segments in Agriculture Summarize non-buffered Total Length by HUC 11 attribute Summarize Total Length by HUC 11 attribute Divide Summarized Yield by watershed Area = New Yield Incremental Yield due to Agriculture adjusted to HUC 11 Average Each RANK 1-10 Proportion of stream segments non-buffered and in agricultural areas RANK 1-10 Total Rank: Average Wetland, Riparian and Water Quality Ranking Data Layer Intermediate Analysis Final Result Stage Ranking TOTAL Ranking - 11 -
Appendix B CLASSIFICATION USED TO IDENTIFY AGRICULTURAL AREAS Herbaceous Planted/Cultivated - Areas dominated with vegetation which has been planted in its current locations by humans, and/or is treated with annual tillage, modified conservation tillage, or other intensive management or manipulation. The majority of vegetation in these areas is planted and/or maintained for the production of food, feed, fiber, or seed. 81 Pasture/Hay - Grasses, legumes, or grass-legume mixtures planted for livestock grazing or the production of seed or hay crops. 82 Row Crops - All areas used for the production of crops, such as corn, soybeans, vegetables, tobacco, and cotton. 83 Small Grains - All areas used for the production of graminoid crops such as wheat or rice. 84 Bare Soil - Areas within planted or cultivated regions that have been tilled or plowed and do not exhibit any visible cover of vegetation. - 12 -
Appendix C - 13 -
Appendix D - 14 -
Appendix E - 15 -
Appendix F - 16 -