Assessing Eco-geomorphological Condition of Stream Restoration Projects in North Carolina

Projects to enhance stream ecological and morphological conditions are becoming prevalent around the world. Stream restoration efforts are employed to enhance water quality, better manage riparian zones, improve in-stream habitat, optimize fish passage and to reduce streambank erosion. Many resource management agencies have realized the need to ensure that projects are meeting their intended objectives. The research effort described here developed and evaluated field assessment methods for measuring functional uplift in order to advance the practice of stream restoration. A team of faculty and students visited 157 restored, impaired and reference streams throughout North Carolina during 2006-2012. Five stream assessment methods, including two newly developed assessment methods, were applied and evaluated by comparing to macroinvertebrate metrics. A variety of stream conditions was assessed to capture variability in eco-geomorphological conditions and to establish reasonable expectations for the potential of restored streams. Macroinvertebrates were sampled from 85 restored streams, restoration design data were compiled for 79 streams, and watershed assessment was conducted for 130 streams. Multivariate statistical analyses were performed in order to (1) compare the stream assessment methods, (2) evaluate correlation between stream assessment variables and the macroinvertebrate community metrics, (3) compare the condition of restored streams to impaired and high quality reference channels, (4) develop a "scale" for evaluating restoration need and condition, and (4) to describe relationships among watershed, landscape, and stream design parameters and the resulting eco-geomorphological conditions of restored streams.;At 65 restored streams, five rapid stream assessment methods were applied, including two new procedures: the Eco-Geomorphological Assessment (EGA) and the Stream Performance Assessment (SPA) and three existing stream assessments: USEPA's Rapid Bioassessment Protocol, USDA's Stream Visual Assessment Protocol and the Riparian Channel and Environmental Inventory. Using principal component analysis (PCA) and principal component regression (PCR), all five assessment methods were found to correlate to some macroinvertebrate metrics. Adding watershed condition variables to the PCA improved correlations. In contrast, the age of restoration was not significantly related to macroinvertebrate metrics.;Ordination of the SPA data from 156 streams indicated that restored streams align more closely with reference streams rather than impaired streams. Further, factor analysis revealed that restored streams have morphologic conditions similar to reference streams but exhibit greater variability in aquatic habitat and bedform. Ridge regression was used to predict EPT taxa for restored streams. The model was then used to predict EPT taxa for impaired and reference streams. Predictions indicate that urban streams (>10% impervious) have lower expected numbers of EPT taxa, and rural restored streams have EPT numbers similar to those of rural reference streams.;PCR revealed correlation of morphological design and landscape variables to EGA scores and to macroinvertebrate metrics (n=79 restored streams). Correlation was strengthened by adding watershed variables. Ridge regression was used to predict dominant EPT taxa. The model indicates that larger (wider) streams in steeper valleys with larger substrate and un-developed watersheds have higher numbers of EPT taxa. Also, greater floodplain widths correlate with higher EPT taxa. In addition, it appears that high width to depth ratios and high levels of sinuosity result in lower EPT taxa numbers.;This research effort indicates that project managers must consider watershed condition when determining appropriate metrics for measuring functional uplift of streams. Macroinvertebrate metrics may not be used to gauge uplift in urban streams. It appears that project designers and contractors are successfully establishing stable streams with good geomorphic form and function; however, some projects do not exhibit specific habitat and bedform that may support a diverse aquatic ecosystem. Further, when selecting and designing sites, high priority should be placed on ensuring adequate floodplain width relative to the stream channel width.