Identifying sites for riparian wetland restoration: Application of a model to the Upper Arkansas River basin

We present a conceptual model for identifying restoration sites for riparian wetlands and discuss its application to reaches within the Upper Arkansas River basin in Colorado. The model utilizes a Geographic Information System (GIS) to analyze a variety of spatial data useful in characterizing geomorphology, hydrology, and vegetation of riparian wetland sites. The model focuses on three basic properties of riparian wetland sites: relative soil moisture, disturbance regime, and vegetative characteristics. A relative wetness index is used to define nominal soil moisture classes within the watershed. These classes generally coincide with uplands (low), channel margins (moderate), and channels or open water (high). Vegetative conditions are characterized using color infrared aerial photographs. Land cover types are grouped into five major land cover classes: riparian, moist herbaceous, bare ground, upland, and open water. Disturbance regime is characterized by a reach-based index of specific power (omega). Preliminary results indicate that reaches within the Upper Arkansas River basin can be classified as high energy (omega greater than or equal to 8 W/m(2)) or low energy (omega less than or equal to 3W/m(2)), using discharge estimates that reflect the 10-year flood event. Field surveys of channel and flood-plain conditions show that high-energy reaches (omega greater than or equal to 8 W/m(2)) are characterized by sites where the channel occupies a large proportion of the valley bottom. By contrast, low-energy reaches (omega less than or equal to 3 W/m(2)) are characterized by meandering channels with wide alluvial valleys. Restoration potential is evaluated as a combination of nominal scores from wetness, land cover, and disturbance indices. Application of these methods to field sites within the Upper Arkansas River basin identifies a wide range of riparian wetland sites for preservation or restoration. Potential sites within identified reaches are prioritized using size and proximity criteria.