Integrating Hydrologic, Geomorphic, and Ecological Assessment at the Watershed Scale


Hydrologic and ecological systems are physically linked along riparian corridors through fluvial geomorphic systems.  Riparian zones are defined as those areas of, on, or relating to the banks of a natural course of water.  Information about the geomorphic structure of riparian corridors is thus necessary to evaluate interactions between hydrological and ecological systems. Geomorphic characterization of stream reaches provides the means to evaluate their present condition, and to parameterize models that can be used to predict changes in that condition (geomorphic response). 


At the watershed scale, tools for integrated hydrologic, geomorphic, and ecological assessment would permit the evaluation of currently degrading reaches, as well as those that are likely to degrade as a result of proposed, planned, or forecasted land-use or climate change.  As such, they could be used to identify areas where limited resources available for field investigations and restoration efforts can be focused to maximum effect.  In addition, they could be used in planning efforts to evaluate potential impacts from various proposed alternatives.  These watershed-scale investigations may be linked to provide multi-scale assessment for integration with landscape analyses.


Independent research funded by the U.S. Army and U.S. EPA has resulted in the development of two tools that, if integrated, could facilitate integrated hydrologic, geomorphic, and ecological assessment at the watershed scale.  A watershed-based geomorphic modeling tool, AGWA-G was developed at the USDA-ARS Southwest Watershed Research Center with funding from an IAG with the U.S. EPA (DW12939409-01-2, Landscape Indicator Interface with Hydrologic and Ecological Models).  Development and testing of this tool revealed that a significant obstacle to practical application of AGWA-G was the lack of any automated means of extracting geomorphic (channel-geometry) information for large areas from remotely-sensed data.


A partially-automated procedure for channel cross-section extraction and morphologic characterization was developed at the University of Wyoming with funding from the U.S. Army.  This procedure enables a skilled user to interact with a geographic information system (GIS) and a database of channel profile data to determine the effective width, depth, and cross-section area at any given point.  Used independently, this tool is useful for extracting information from high-resolution DEMs.  Additional work is required to permit reach-based geomorphic characterization, and automation is necessary before the tool can be applied on a watershed scale.


The funding will be used to research and develop a fully automated version of the morphologic characterization tool (MCT) for use with the AGWA-G geomorphic modeling tool.  MCT will automate the determination of channel morphometric properties for input into relevant models and assist in the validation and further development of AGWA-G.  Integration of AGWA-G and MCT will provide a means to characterize stream reaches throughout a channel network, and parameterize hydrologic and geomorphic simulation models.  By integrating reach-scale riparian-zone characterization and watershed-scale hydrologic and geomorphic modeling, this tool provides the foundation for much additional research on the linkages between hydrologic and ecological systems.


High-resolution remotely-sensed information is becoming more widely available, and the available tools that can extract and utilize the information it provides are limited.  In addition to surface-elevation information, certain data products such as light detection and ranging (LIDAR) data can be used to characterize the composition and structure of riparian ecological communities.  Preliminary testing of AGWA-G and MCT was conducted using a 1-meter resolution dataset acquired with LIDAR in the USDA-ARS Walnut Gulch Experimental Watershed.  A second overpass is scheduled for Fall, 2004, the data from which will provide an opportunity to validate AGWA-G and research the effectiveness of change detection using MCT on a reach basis.  These data will be available for this project through the Army-funded project and represent significant leveraging.




(1) Develop an automated tool for channel morphologic characterization on a reach-average basis.  The tool must be able to be called from ArcView or ArcGIS, passed information about the reach definitions from the watershed delineation, and return a geomorphic/geometric characterization that can be used by other models.


(2) Revisit and survey monumented cross-sections on Walnut Gulch in conjunction with a second LIDAR overflight.




(1) Deliver a Beta version of an ArcView- or ArcGIS-based automated channel-morphologic characterization tool.