Bedload Composition and Development of 2D Stream Sediment Model for Stream Restoration Design Applications in Urbanizing Watersheds

A central problem in the field of stream restoration is that of designing a stable channel that supports a healthy benthic population. Many stream restoration projects take place in urban or urbanizing watersheds. The relationship between changing watershed characteristics and local channel conditions within that watershed is poorly understood. This study is made up of two major components that address aspects of this problem: first, a physical study of bedload flux in watersheds representing rural, urban, and developing conditions and second, verification of results from the Computational Hydraulic Engineering Two-Dimensional Sediment Model (CCHE2D) on the reach scale and correlation of CCHE2D results with Rapid Bioassessment Protocol III (RBP III) scores. Study sites were selected in Knox County, Tennessee including twelve sites for the bedload study and a single site for the CCHE2D model verification. The bedload flux portion of the study combines field collection of bedload via portable bedload traps and an estimate of energy slope from peak stage recorders. Information derived from the field collection will be combined with watershed data via geographic information system (GIS) analysis. Watershed metrics including percent impervious area, roadways adjacent to streams, and average watershed slope determined via GIS will be correlated with the measured bedload composition for each research site. The CCHE2D model verification will combine the study of bedload flux with a previous study correlating the surficial bed material composition with macroinvertebrate biotic integrity scores (RPB III) for 76 reaches in East Tennessee. The combination of this information will provide a valuable tool in stream restoration design in allowing practitioners to have an empirical metric with which to design/predict channel substrate composition as an indicator of physical habitat quality.