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ASSESSING ARID RIPARIAN LANDSCAPES USING REMOTE SENSING: THE FIRST STEP
Citation:
TallentHalsell, N G., M. E. Hamilton, L. Bice, AND R D. Lopez. ASSESSING ARID RIPARIAN LANDSCAPES USING REMOTE SENSING: THE FIRST STEP. Presented at Riparian Habitat and Floodplains Conference, Sacramento, CA, March 12-15, 2001.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
Riparian ecosystems are of great value in the Southwest yet they are also extremely fragile and susceptible to natural and anthropogenic disturbances. Riparian ecosystems establish in patterns per the hydrologic and geomorphologic processes that dictate terrestrial plant succession. These patterns may translate into metrics (e.g., size, shape, perimeter-area ratio) that reveal the ecological integrity of the watershed. Southwestern riparian ecosystems, although scattered and isolated, appear as discrete, discernible patches when viewed against the backdrop of the adjacent and uplands. However, when using remote sensing data, spatial resolution imposes the scale at which these patches may be detected. Our research addressed the utility of using remote sensing for detection and characterization of small, scattered riparian patches. We compared the resource and financial costs associated with an inventory of riparian ecosystems in southwestern Arizona across several spatial resolution scales using satellite imagery and aerial photography. In addition, we identified the poorest resolution acceptable to reveal the shape and extent of riparian patches along perennial and intermittent surface waters in these regions. The coarse spatial resolution of satellite imagery (Landsat Multi Spectral Scanner data, resampled to approximate a 60 m x 60 m spatial resolution; Landsat Thematic Mapper, 30 m x 30 m spatial resolution) was adequate for the detection of most
riparian ecosystems (due to their sharp spectral reflectance contrast with surrounding desert vegetation) yet inadequate for patch characterization since it exceeded the physical dimensions of the vegetation and distorted the boundaries of riparian patches less than 60 or 30 m' in area. Thus, satellite imagery was used to provide a gross inventory of riparian patches while aerial photographs were still needed to accurately map and delineate the actual
patch characteristics. It is expected that future systems with improved spatial and spectral resolution (e.g., IKONOS, SPIN, Orb-View 3, SPOT 5; e.g., AVIRIS, Hymap and CASI) will provide the fine scale imagery necessary for the calculation of riparian landscape metrics.