Hurricane Harvey Caused Unprecedented Freshwater Inflow to Galveston Bay

Abstract

Hurricane Harvey heavily impacted Texas in August 2017 due to an extreme amount of rainfall, especially in the large metropolitan area in and around Houston. There was an offshore storm surge associated with Harvey, and while it raised the water level in the bay, possibly prolonging flooding in the Houston area by slowing drainage, it was not responsible for flooding, as water flowed continuously out of the bay during peak flooding. Salinity measured near the mouth of the San Jacinto river dropped to 0 from 15 psu in 1.5 days after the start of storm-related outflow from the bay; the whole bay was fully freshened in 3.6 days. Depth-averaged outflow from the entrance channel reached 2 m/s. Using publicly available oceanographic data within Galveston Bay, we estimate the amount of freshwater that flowed into the bay from this rainfall to be 17 ± 5 km3 (14 million acre feet), or about 5 times the volume of Galveston Bay itself. This is less than, but close to, the freshwater input source: 20 km3 of rain that was estimated from Doppler radar to have accumulated in the drainage basins contributing to the bay. By comparison, the freshwater inflow estimates by the Texas Water Development Board (TWDB) predicts 13 km3 (11.5 million acre feet) of inflow to Galveston Bay during Hurricane Harvey.