Sediment routing in an incised valley during Hurricane Harvey (2017) in Houston, Texas, USA: Implications for modern sedimentation

Southeastern Texas (United States) recorded one of the largest flooding events in U.S. history during Hurricane Harvey (25−31 August 2017), mobilizing millions of cubic meters of sediment in Houston fluvial-estuarine systems. We conducted an integrated quantitative analysis to determine the net minimum volume of sediment transported during the storm using subaerial elevation change, satellite and ground-based images, and sediment dredging reports along major waterways. The 12 fluvial-estuarine streams and two controlled reservoir drainages in the Houston area transported a minimum of ∼2.723 × 107 m3 of sediment. This volume is ∼6−51 times larger than the average annual volume of sediment delivered to Galveston Bay in modern times (in the past 200 yr), and ∼30−118 times larger when compared to Holocene rates. Nearly ∼26% of the measured volume was deposited in Addicks and Barker reservoirs, decreasing holding capacities by ∼1.2% and ∼1.6%, respectively. In the stream drainages, sediment was mobilized from west-northwest of Houston and pulsed toward Galveston Bay, highlighting the extreme short-term variability in sediment delivery. Sediment flux through the Houston region during Harvey is an example of sediment storage followed by a pulsed delivery of high sediment volume rather than continuous delivery of sediment. Comparison of sediment volumes transported through natural and modified drainages through Houston demonstrates that channel modification resulted in significant bypass of sediment downstream. Urban watershed management is more effective when continual updates are implemented based on regional circumstances rather than based on historical fluxes.