2004 Progress Report: Linking Land Use Change, Stream Geomorphology, and Aquatic Biodiversity in a Hierarchical Classification SchemeEPA Grant Number: R830595
Title: Linking Land Use Change, Stream Geomorphology, and Aquatic Biodiversity in a Hierarchical Classification Scheme
Investigators: Watzin, Mary C. , Hession, W. C. , Keeton, William S. , Troy, Austin R.
Institution: University of Vermont
EPA Project Officer: Hiscock, Michael
Project Period: December 1, 2002 through November 30, 2005 (Extended to November 30, 2006)
Project Period Covered by this Report: December 1, 2003 through November 30, 2004
Project Amount: $664,339
RFA: Development of Watershed Classification Systems for Diagnosis of Biological Impairment in Watersheds (2002) RFA Text | Recipients Lists
Research Category: Water and Watersheds , Water
The goal of our research project is to develop and evaluate a watershed and stream reach classification system based on the relationship between land-use change, river geomorphic condition, riparian habitat fragmentation, and riverine ecological condition. The specific objectives of this research project are to: (1) determine which geomorphic classes, beginning at the finer scale, can be consistently related to the ecological condition of a stream reach; (2) determine what land-use metrics, expanding to a coarser scale, best predict those geomorphic classes that consistently relate to ecological condition; (3) evaluate the ability of our classification system to target sites in greatest need of watershed management and stream restoration based on current land use and geomorphology; (4) develop and evaluate the ability of our classification system to identify sites in need of conservation based on predicted land-use change and resulting effects on geomorphology and aquatic ecology; and (5) develop a general framework for the Vermont Department of Environmental Conservation and others to use the resulting classification system as a foundation for statewide watershed protection, management, restoration, and education.
During Year 1 of the project, we focused on field work to support specific Objective 1 and the development of an updated land-use/land-cover map and a land-use change map for our study region. During Year 2 of the project, we continued data collection in support of specific Objective 1, began analysis addressing specific Objective 2, and constructed preliminary models for specific Objective 3.
Twenty-five sites now have been sampled. These sites span a range of geomorphic conditions. At each site, a geomorphic assessment, habitat assessment, riparian vegetation survey, and biological assessment were conducted.
Longitudinal profiles and the cross-sections were surveyed using a laser level. Water surface and thalweg elevations were recorded at feature locations such as top of pool, deep point of pool, and top of riffle along the entire reach. For the cross-sections, six locations per reach were surveyed, including three riffles and three pools. Two cross-sections were chosen for additional erosion sampling and as permanent sites to allow for future surveys to assess channel change over time.
A Rapid Geomorphic Assessment sheet was completed for each reach according to the Vermont Agency of Natural Resources Phase 2 Protocols. Each site was rated on a scale of 0-20 (0 = poor, 20 = optimal/reference) in four categories: degradation, aggradation, channel widening, and planform change for a possible total of 80 points. The purpose of this assessment was to determine the overall condition of the stream and identify the dominant adjustment process occurring within the stream. Erosion pins were installed along each reach in eroding banks and sediments were sampled for particle size distribution and phosphorus analysis. Soil and Water Assessment Tool (SWAT) modeling is underway.
Habitat features measured included wetted bed width, water depth, flow velocity, embeddedness of cobble and gravel materials, particle size, bed compaction, deposition of fine silt, and size and number of large woody debris. An instream Vermont Rapid Habitat Assessment also was conducted, and the number of riffles, runs, and pools; length of riffles and runs; pool dimensions; distance between riffles; weight of dried leaf detritus samples; periphyton density; and length of exposed bank on both sides also were quantified.
A stratified sample of plots in upland forests, floodplain forests, and floodplain non-forested patches at each site were characterized. Vegetation density, canopy structure, percent cover of herbaceous vegetation, course woody debris volume and density, leaf area index, and light intensity were measured in each plot, as appropriate. Preliminary analyses show significant correlations between some measures of vegetation structure and geomorphic condition.
Macroinvertebrates were sampled at six regularly spaced intervals along the length of the stream reach using a 500 µm mesh Surber sampler. Samples are being completely enumerated and identified as: (1) one of the orders of Ephemeroptera, Plecoptera, or Trichoptera (EPT); (2) one of the Chironomidae family; (3) one of the Oligochaete genera; or (4) other. Taxon richness, evenness, and assemblage abundance will be calculated. Fish were sampled by seine in three to four representative pools or slow runs in each reach. The first 150 fish of each collection effort were identified to species, weighed to the nearest 0.1 g, and measured to the nearest 1.0 mm. Bird communities were surveyed using the double-observer method at all sites. The species, gender, and location of each individual were recorded, as well as the vegetative community in which it was sighted (if applicable). We are using a variety of multivariate methods to explore the relationships between geomorphic and habitat measures and biodiversity across a functional and taxonomic range.
Preliminary results show that geomorphic condition significantly influences fish community diversity, productivity, and condition. Geomorphic condition and characteristics have been combined to explain 31 to 44 percent of the variance observed in assemblage diversity and biomass. Two multifactor indices of fish community diversity, H’ (Shannon-Weiner) and 1/D (Simpson), are negatively associated with geomorphic deviation: the greater the deviation from reference geomorphic conditions, the lower the observed fish community diversity. A variety of habitat variables also proved significant in explaining variance seen in bird abundance and diversity. In addition to instream habitat, channel morphology (e.g., entrenchment ratio, width:depth ratio, sinuosity) and characteristics of riparian vegetation (e.g., % forest, % conifers) were particularly important.
Geographic Information System (GIS) and Land-Use Change Analysis
A land-use/land-cover map for 2002 and a change detection map based on Landsat Thematic Mapper Satellite imagery from 1990 and 2002 have been created for the study region. The accuracy assessment for land-use change in Chittenden County, the most urban county in the study area, indicated an acceptable accuracy rate. In the more rural Addison and Lamoille counties, however, the Feature Analyst results were less impressive. We currently are working to improve these results. Modeling using UrbanSim to predict future trends in urban development is underway.
We will address specific Objectives 3, 4, and 5 during Year 3 of the project. Multivariate techniques will be used to quantify the relationships between land use, forest fragmentation, riparian zone fragmentation, geomorphic condition, and aquatic biodiversity. Land-use change modeling in GIS will be used to identify land areas that contribute to watershed impairment and to rank hydrologic units according to their current and projected future ecological impairment. A hierarchical series of models will be developed to explore the direct and indirect connections between the biological, geomorphic, riparian, and land-use parameters. Five additional stream reach sites will be sampled during the spring and summer of 2005 to help validate our models. The final classification system will group stream reaches and watershed units by their current and predicted future ecological integrity or degree of biological impairment.