Monitoring streambank properties and erosion potential for the restoration of lost creek

Lost Creek runs through the main campus of Rose-Hulman Institute of Technology and continues through Vigo County until it deposits into the Wabash River near Terre Haute, Indiana. The focus of this investigation was on the reach of Lost Creek that flows through the Rose-Hulman campus. This portion of the creek currently shows signs of incision with the channel bed degrading and the banks undercutting and mass wasting. The continued development of this incision will prove to be detrimental to campus infrastructure. There are already signs of foundational failure of one pedestrian bridge within the reach. In a concurrent study, a restoration/demonstration design to stabilize Lost Creek is being developed using a process based (analytical) approach. The goal of this paper is to present the results of a study conducted to support design methods that are focused on bank stability and erosion. The study was conducted to classify bank stability and bank soil properties throughout the reach to support the application of the Bank Stability and Toe Erosion Model (BSTEM). The BSTEM model requires various soil properties to calculate stable bank slopes with respect to fluvial erosion and geotechnical failure. The necessary properties to apply BSTEM are pore water pressure, critical shear stress (τ_c), erodibility coefficient (k), friction angle (), cohesion (c'), relation between shear strength and matric suction (^b), and saturated unit weight. Tests were conducted to determine these properties for each soil layer within the vertical profile of four cross sections defined within Lost Creek. In addition to the soil properties needed for BSTEM, testing of the plasticity and liquid limits (Atterberg Limits), bulk density, water content, dispersion ratio, soil activity, silt-clay and the shear strength were also conducted. The results showed a wide range of soil types and parameters are present in the short reach. This further warrants the use of a process based restoration design approach to account for this variability.