Abstract: Session B 9:30 am (Back to Session B)
Floodway Improvements and Habitat Restoration Post-Disaster, Howards Creek, WV
Timothy A. Denicola
Civil & Environmental Consultants, Inc.
Bridgeport, West Virginia
Authors: Timothy A. Denicola, Nathan S. Ober, Robert Stewart
Howards Creek in White Sulphur Springs, West Virginia, was catastrophically impacted in 2016 by a presumed 1000-year flood. Following the disaster the West Virginia Conservation Agency (WVCA) requested ecosystem restoration services to facilitate two improvements, increased flood capacity and improved aquatic habitat.
Civil & Environmental Consultants, Inc. (CEC) collected aerial LiDAR and orthoimagery and conducted a geomorphic survey in collaboration with WVCA along an approximate 4400-foot reach of Howards Creek. Existing conditions and proposed design parameters were derived using a combination of software including, but not limited to: RIVERMorph 5.2.0, AutoCAD Civil 3D 2018, and SRH-2D Sediment and River Hydraulics software. United States Geological Survey (USGS) Scientific Investigation Reports were referenced to verify discharge calculations.
Existing and proposed channels were modelled using the United States Bureau of Reclamation’s SRH2D hydraulic modelling software. Model outputs confirmed field measurements and produced shear stress maps displaying mobilized particle median diameter. Hydraulic model results ensure even energy dissipation to stabilize sediment routing.
Flooding at recurrence intervals greater than 1.5 years have been exacerbated by aggradation either due to flood deposition or anthropogenic impacts. Restoration design increases bankfull area and modifies width-to-depth ratio to ensure smooth transition at tie-ins while optimizing sediment transport capacity. An inner-berm increases base flow depth for fish passage and further facilitates sediment transport. Hydraulic structures facilitate deposition, promote inner berm development, maintain desired pool spacing and dimensions for energy dissipation, reduce near bank stress, diversify the bed form, and produce scour pools of cobble substrate. Tributary structures maintain grade at tie-ins. Toe wood with live brush layering and root wads reduce near bank velocity and creates substantial habitat in oxygenated pools.
A combination of Priority Level II and III restoration approaches were utilized to increase floodplain capacity and sinuosity on Reach 1 and to accommodate geographic constraints including housing and constructed levees on Reach 2. Additionally, an offset berm fills a low-elevation area and redirects floodwaters back into the proposed channel. The final restoration design creates improved geomorphic stability, sediment transport, bed form diversity, and habitat while effectively conveying base flow and floodwaters.