Collaborative Research: Reevaluating precipitation extremes and flood hazard in the wake of Hurricane Harvey

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In August 2017, Hurricane Harvey produced catastrophic flooding across southeast Texas that caused over $100 billion in damages. Rainfall totals and river flows associated with Hurricane Harvey shattered records across southeast Texas, but these records span only the last ~100 years. How unusual was the flooding generated by Hurricane Harvey, and what is the likelihood of such an event occurring again? The brevity of instrumental hydrologic records currently limits our ability to precisely answer this critical question. This project will improve risk assessments for extreme precipitation and flooding in southeast Texas by extending the length of the hydrologic record back in time using geological evidence of flooding with a hydrologic model. These data will allow us to better understand the probability of an event like Hurricane Harvey occurring again, and evaluate how variations in climate and human activities affect flood risk in southeast Texas. This research will improve assessments of the risk posed by flooding, a hazard that has recent affected millions of people living in the Houston metropolitan area. The project will engage undergraduate and graduate students in research, and its findings will be disseminated to the public and decision-makers through the Center for Texas Beaches and Shores.Frequency analyses based on a century of hydrological measurements estimate that the recurrence intervals of Hurricane Harvey?s precipitation and discharge maxima approach 1,000 years (i.e., 0.1% exceedance probability), but these estimates are highly uncertain with 95% confidence intervals that span multiple orders of magnitude. The goal of this project is to reevaluate flood hazard in the Houston metropolitan area by extending the temporal range of analysis from ~100 years to ~1,000 years. To do this, we will use established techniques in paleoflood hydrology to reconstruct discharge maxima of the two rivers in southeast Texas over the last millennium, and integrate these data with a hydrologic model to evaluate the roles of natural and anthropogenic forces on regional flood hazard. These data will allow us to (a) improve assessments of the exceedance probability of Hurricane Harvey and other recent catastrophic floods in the Houston metropolitan region, (b) test for the presence of non-stationarities in flood hazard, and (c) identify the roles of climate variability and land use and land cover change in generating discharge extremes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.