Ward et al., 2018

Paper/Book

Streambed Restoration to Remove Fine Sediment Alters Reach-Scale Transient Storage in a Low-Gradient Fifth-Order River, Indiana, USA

Ward, A.S., Morgan, J.A., White, J.R., and Royer, T.V. (2018)
Hydrological Processes  

Abstract

Hyporheic restoration is of increasing interest given the role of hyporheic zones in supporting ecosystem services and functions. Given the prevalence of sediment pollution to waterways, an emerging restoration technique involves the removal of sediment from the interstices of gravel‐bed streams. Here, we document streambed sediment removal following a large, accidental release of fine sediment into a gravel‐bed river. We use this as a natural experiment to assess the impact of fine sediment removal on reach‐scale measures of transient storage and to document the responses of reaches with contrasting morphology (restored vs. unrestored) to changing discharge one‐field season. We conducted a series of conservative solute tracer experiments in each reach, interpreting both summary statistics for the recovered in‐stream solute tracer time series. Additionally, we applied the transient storage model to interpret the results via model parameters, including a Monte Carlo analysis to measure parameter identifiability and sensitivity in each experiment. Despite the restoration effort resulting in an open matrix gravel bed in the restored reach, we did not find the significant differences in most time series metrics describing reachscale transport and transient storage. We hypothesize that this is due to enhanced vertical exchange with the gravel bed in the restored reach replacing lateral exchange with macrophyte beds in the unrestored reach, developing a conceptual model toexplain our findings. Consequently, we found that the impact of reach‐scale removal of fine sediment is not measureable using reach‐scale solute tracer studies. We offerrecommendations for future studies seeking to measure the impacts of stream restoration at the reach scale.
 

Citation

Ward, A.S., Morgan, J.A., White, J.R., and Royer, T.V. (2018): Streambed Restoration to Remove Fine Sediment Alters Reach-Scale Transient Storage in a Low-Gradient Fifth-Order River, Indiana, USA. Hydrological Processes. DOI: 10.1002/hyp.11518