Assessing Forest Riparian Buffer Zones in the Chesapeake Bay Watershed
A forest riparian buffer is an area whose vegetation is trees which is located between a stream and the adjacent uplands. These areas are often managed in ways that help ensure the hydrologic and ecological integrity of stream channels, and aid in curtailing upland sources of pollution by trapping, filtering and transforming pollutants before they reach stream surface waters. In the past 10 years, the DoD has invested significant resources restoring these areas not only to improve habitat and water quality on and flowing from their lands, but also to help meet Chesapeake Bay Agreement Goals for riparian buffers, nutrient and sediments. Researchers at Ecosystem Solutions have closed a grant funded by the DoD Legacy Resource Management Program to help monitor these sites and ascertain if the restored areas are functioning properly. Below, read about how researchers at Ecosystem Solutions are accomplishing this.
Water Quality
One way to test if restored forest riparian buffer zones are functioning properly is to test the water quality in the stream. Since one of the many functions of the riparian zone is to help filter both nutrients (nitrogen and phosphorus) and sediments from water moving across the land to the stream researchers are collecting several water quality parameters (Table 1). To collect water quality samples, researchers used a Yellow Springs Instrument and took grab samples that were sent to the Analytical Services Laboratory at the University of Maryland Chesapeake Biological Laboratory.
Instream Water Quality |
Laboratory Analyzed Water Quality |
| Dissolved Oxygen (mg/l) | Ammonia - NH4 (mg/l) |
| Dissolved Oxygen (% saturation) | Nitrate – NO3 (mg/l) |
| Conductivity | (Soluble Reactive Phosphorus – PO4 (mg/l) |
| Salinity | Total Phosphorus – TP (mg/l) |
| Temperature (°C) | Total Suspended Solids – TSS (mg/l) |
Researchers intend to see improving water quality with age of restored buffer as well as the condition of the buffer itself. Generally speaking, we expect to see lower concentrations for all of the laboratory analyzed parameters, with increasing dissolved oxygen, and lower temperatures. Because underlying geology plays a large role in the concentration of dissolved ions in a stream, we expect to see a wide variety of conductivity and salinity values because the sample areas cover both the Piedmont and Coastal Plain physiographic regions.
Benthic Macroinvertebrates
Benthic macroinvertebrates should be deemed "mother nature's water quality indicators". These tiny creatures reside in the bottom (benthos) of the stream, and are sensitive to changes that occur over time, including changes in water quality and available habitat. Benthic macroinvertebrates include larval and adult insects, worms, other crustaceans, and mollusks. These organisms can be differentiated based on their preferred habitat, mode of feeding and type of diet, and tolerance to pollution (organic, nutrients enrichment and increased sediments). Since riparian buffer zones have to ability to affect all three of these, collecting and identifying benthic macroinvertebrates from a site is an excellent way to determine the health of the system (Table 2).
| Poor Water Quality Indicators |
Medium Water Quality Indicators |
Good Water Quality Indicators |
| Some oligochaetes (wors) | Amphipod (scud) | Perlodidae (stone fly) |
| Chironomidae (midge) | Tipulidae (fly) | Leutricidae (stone fly) |
| Lestidae (dragonfly) | Hydropsychidae (caddis fly) | Ephemerellidae (may fly) |
| Isopods (rolypoly) | Elmidae (beetle) | Glossosomatidae (caddis fly) |
| Staphylinidae (beetle) | Gerridae (water bug) | Corydalidae (Dobsonfly) |
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Once researchers identify benthic macroinvertebrates, the data are used to calculate metrics that are based on the above criteria as well as their abundance and diversity. These metrics are then used to determine the relative "health" of the stream; water quality and quality and amount of available habitat. This in turn can give us an indication of how well the restored buffer is working, or if modifications need to be made.
Habitat
Another way to determine if a restored buffer is doing its job, is to perform a habitat assessment. Habitat assessments “grade” the types and quality of stream and riparian habitat. Many indicators of habitat quality are dependant on the existence of a healthy riparian zone. A healthy riparian zone not only helps filter sediment from overland flow so it does not bury essential habitat (rocks, stones and woody debris), but also helps stabilize the stream banks to help curb erosion, contributes food and large woody debris, and shades the stream to keep down temperatures. By using the habitat assessment for both high and low gradient streams from Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish, Second Edition (Barbour et al 1999), researchers were able to score each stream based on 10 instream and riparian indicators (see http://www.epa.gov for a downloadable version of the protocols).
Final Report
All of the field collections for this study were done in the spring of 2006 and 2007. Researchers at Ecosystem Solutions visited over 30 sites from Carlisle, PA to Norfolk, VA and collected over 300 habitat and water chemistry data points as well as benthic macroinvertebrate samples. Click the links below for a full report or fact sheet on the results of our work.
Learn more about our restoration and assessment programs.