Determining sediment deposition dynamics influenced by check dams in a semi-arid mountainous watershed

Authors: Polyakov, Viktor; Nichols, Mary; Cavanaugh, Michelle

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2024
Publication Date: 2/28/2024
Citation: Polyakov, V.O., Nichols, M.H., Cavanaugh, M.L. 2024. Determining sediment deposition dynamics influenced by check dams in a semi-arid mountainous watershed. Earth Surface Processes and Landforms. 49(6):1849-1857. https://doi.org/10.1002/esp.5802.
DOI: https://doi.org/10.1002/esp.5802

Interpretive Summary: Sediments stored in depressions contain a record of long term landscape erosion as well as evidence of major natural and anthropogenic disturbances. Accurate sediment chronologies are critical for interpreting these records. In this study sedimentation rates behind a series of check dams in an area heavily affected by mining were determined using 137Cs isotope. Long term deposition trends, dam fill rate, and changes in sediment composition were identified in the chronosequence. This approach helps to better understand the efficiency of check dams in controlling sediment fluxes over multiple decades and improve planning and design.

Technical Abstract: Semi-arid environments are characterized by infrequent large magnitude rainfalls that produce flash flood events with high sediment concentration. Control structures such as check dams are widely used in this environment for mitigation. However, their impact on the overall sediment balance of watersheds, particularly those severely affected by anthropogenic activity, is sparsely documented. This study used topographic measurements, sediment analysis, and fallout isotope techniques to assess the effectiveness and service life of 18 rock and masonry check dams that were constructed in the 1930s for controlling sediment fluxes in an 11 ha mountainous watershed in southern Arizona. All of the dams are currently filled with sediment resulting in reduction of local channel gradients by 35 to 71% to between 0.04 and 0.28 depending on location within the reach. Sedimentation occurred over multiple decades at a relatively slow average rate of 0.59 t ha-1 y-1 indicating low instantaneous retention efficiency. The smaller headwater dams were filled soon after construction, however their share of the overall storage capacity was minor. Although evaluation of 137Cs was an effective method for dating sediment, the 210Pb dating method was not satisfactory due to sediment sorting effects and complex deposition patterns. The abundance of similar control structures in the region points to the opportunity to better understand the process impacts of check dams over multiple decades to inform planning and design of their use in future mitigation projects.