INTEGRATED ASSESSMENT STRATEGY FOR EVALUATING ECOLOGICAL CONDITIONS OF SOUTHWESTERN BOTTOMLAND ECOSYSTEMS

Numerous strategies have been developed over the last few decades to evaluate stream conditions. Unfortunately, many of these strategies are limited with regard to the information they provide to site managers seeking to develop effective, long-term stream restoration strategies. Major criticisms of the past evaluation strategies are that they (1) have a myopic focus on short stream reaches, (2) use subjective protocols (i.e., scorecard approach) and time-dependent methods (different results may be obtained depending on when the stream reach was assessed), (3) rely on an assumption that similar geomorphic processes affect channel form across different climates, (4) depend on identification of such channel features as bank full (extremely difficult for alluvial streams in arid climates), and (5) are based on an overall approach that is not supported by a thorough understanding of geomorphic processes.

Given the ecological deterioration that has beset many bottomland ecosystems throughout the semi-arid southwestern U.S., developing a bottomland evaluation strategy is a critical priority. In response, technical personnel from both the public and private sectors have been working over the last few years to develop step-by-step, field-based protocols for evaluating the biophysical conditions of bottomland ecosystems (the rivers and the biotic communities they support) in water-deficient areas. This paper reviews the integrated evaluation approach in the context of how it was used to design and implement rehabilitation efforts along the Little Colorado River, Hunt Valley, Arizona. Key objectives of the integrated evaluation approach are to provide information for understanding the bottomland's biophysical conditions, the physical processes that shape them, the extent that both conditions and processes have changed, and the reasons for the changes that have occurred. With regard to the Little Colorado River case study, the elements of the integrated evaluation approach that will be highlighted include, evaluating: land-use change across the watershed, morphologic change along the mainstem and principal tributaries, streamflow and shallow ground-water conditions, bottomland soil and plant-community characteristics.