FLOODSSediment Movement During Hurricane Harvey Could Negatively Impact Future Flooding
Enormous amounts of sediment, or sand and mud, flowed through Houston waterways during Hurricane Harvey in 2017, due in part to modifications made by humans to bayous, rivers and streams over the past century. Harvey was the largest rainfall event in U.S. history, and it moved 27 million cubic meters of sediment, or 16 Astrodomes, through Houston waterways and reservoirs. This could seriously impact future flooding events and be costly to the City of Houston.
Enormous amounts of sediment, or sand and mud, flowed through Houston waterways during Hurricane Harvey in 2017, due in part to modifications made by humans to bayous, rivers and streams over the past century, that could seriously impact future flooding events and be costly to the City of Houston.
New analysis by geology researchers at the University of Houston found 27 million cubic meters of sediment, or 16 Astrodomes, moved through 12 Houston waterways and Addicks and Barker reservoirs during Harvey, the largest rainfall event in U.S. history. After the storm, up to five feet of sediment accumulated in the Houston Ship Channel, costing $350 million to dredge it back to its pre-Harvey depth. From August 25 to 31 of 2017, the study found, the amount of sediment moved through Houston was equivalent to about 40% of the sediment discharged annually to the Gulf of Mexico by the Mississippi River.
“We found a strong correlation between stream modification and sediment bypass through those streams,” said Andrew Stearns, first and corresponding author of the study, published in the journal “Geology.” He conducted much of the work while earning his master’s degree in the laboratory of Julia Wellner, a contributing author and associate professor of geology at UH’s College of Natural Sciences and Mathematics.
River straightening, a type of artificial stream modification, is an engineering technique used to shorten the distance to the ocean and increase water flow, which reduces flooding in surrounding areas. Straightening can be as minor as removing bank vegetation or as extreme as replacing the banks and channel floor with concrete. The technique was used on Houston’s waterways in the 1940s and ‘50s and opened development areas for additional homes and buildings. However, as the study authors found, an unintended consequence is more sediment moves downstream as well.
“Our study provides policymakers with vital information for sediment management in urban watersheds. Not much attention has been given to sediment management, but it has big implications for the city itself, and can be quite costly when omitted from a watershed plan,” added Stearns.
He and the researchers report sediment deposits during Harvey decreased holding capacities in Addicks and Barker reservoirs by about 1.2% and 1.6% respectively.
