A Morphodynamic Model to Evaluate Long‐Term Sandbar Rebuilding Using Controlled Floods in the Grand Canyon

Abstract

Controlled floods released from dams have become a common restoration strategy in river systems worldwide. Here we present a morphodynamic model of sandbar volume change for a subset of sandbars of the Colorado River in Grand Canyon National Park, where controlled floods are part of a management strategy focused on sandbar maintenance. We simulate sandbars as a triangular wedge, where deposition and erosion are modeled using physically based approaches that are driven by nearly continuous observations of flow and suspended sand concentration. We optimize an eddy exchange coefficient and erosion rate parameter by comparing model predictions to measured bar volumes. The model captures most of the variability in observed volume changes, and demonstrates the importance of flood frequency and sand concentration on average bar size. The model is easily implemented and adaptable, providing a means for predicting the future behavior of sandbars under a variety of streamflow and sediment supply scenarios.

Impeding access to tributary spawning habitat and releasing experimental fall-timed floods increase brown trout immigration into a dam’s tailwater

“…Sci. Downloaded from cdnsciencepub.com by 44.224.250.200 on 03/05/23 successful in enhancing beaches and increasing the prevalence of associated low-velocity backwater habitats (Schmidt and Grams 2011;Melis et al 2015;Mueller and Grams 2021). Initially, it was suggested that increases in such habitat would benefit humpback chub; however, studies to date suggest such impacts are small in comparison to other drivers (Dodrill et al 2015;Yackulic et al 2018;Dibble et al 2021).…”