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Roots of riparian vegetation increase streambank erosion resistance and structural stability; therefore, knowledge of root density and distribution in streambanks is useful for stream management and restoration. The objective of this study was to compare streambank root distributions for herbaceous and woody vegetation and to develop empirical models to predict root density. Root length density, root volume ratio, soil physical and chemical properties, and above-ground vegetation densities were measured at 25 sites on six streams in southwestern Virginia. The Mann-Whitney test was used to determine differences in root density along stream segments dominated by either woody or herbaceous vegetation. Multiple linear regression was used to develop relationships between root density and site characteristics. Study results showed that roots were evenly distributed across the bank face with the majority of roots having diameters less than 2 mm. Soil bulk density and above-ground vegetation were key factors influencing root density. While significant relationships were developed to predict root density, the predictive capabilities of the equations was low. Because of the highly variable nature of soil and vegetation properties, it is recommended at this time that soil erodibility and root density be measured in the field for design and modeling purposes, rather than estimated based on empirical relationships.(KEY TERMS: root length density; riparian buffers; streambank erosion; erosion; fluvial processes; soil erodibility.) Piercy, Candice and Theresa Wynn, 2008. Predicting Root Density in Streambanks.

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This report assesses potential impacts to aquatic resources resulting from proposed navigation channel expansion activities within Mobile Bay, Alabama. This work was conducted for the U.S. Army Corps of Engineers (USACE) Mobile District, to support development of a supplemental Environmental Impact Statement. Changes in water quality and hydrodynamics were evaluated for potential impacts to benthic macroinvertebrates, wetlands, submerged aquatic vegetation, oysters, and fish. The assessment includes extensive characterization of baseline conditions, evaluation of estimated post-project conditions related to aquatic resource habitat (e.g., changes in salinity, dissolved oxygen). An analysis of potential impacts related to a 0.5-m sea level rise (SLR) scenario were also evaluated. Results suggest that no substantial impacts in aquatic resources within the study area are anticipated due to project implementation, as the area of greatest potential changes to environmental conditions are already adapted to natural shifts in salinity (and other factors), and to conditions resulting from the existing navigation channel. Although SLR has the potential to alter aquatic resource habitats with Mobile Bay, additional impacts related to project implementation remain negligible under the 0.5-m SLR scenario. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

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