High Water Marks: Flood Control District Team Working to Help Increase Future Storm Surge Forecasts
How high did the surge get? That simple question is not so simple to answer. While the impacts/damage from surge after a tropical cyclone are essential to document, the more complex problem is determining how high the water actually rose. This has become even more critical as modeling and warnings for surge evolve; accurate post-storm verification of ‘high water marks’ (HWM) will become critical in improving our science and service for future events.
During the historic 2020 hurricane season, a small team from the National Weather Service and the Harris County Flood Control District addressed a variety of technical and logistical challenges to collect accurate HWMs both as a fixed datum as well as above ‘ground’ level (AGL) post hurricanes Hanna, Laura, and Delta, and Tropical Storm Beta. The team collected a total of 180 high water marks: Hanna (40), Laura (60), Beta (18), and Delta (62) over 4 deployments for a total of 10 days. The measurement of a stillwater high water mark in the second floor bathtub of a house in Grand Chenier, LA post Hurricane Laura at 16.9 feet above the ground outside the house was determined to be one of the highest storm surge elevations ever recorded along the Louisiana coast. It is important that accurate post data collection of both storm surge height and inland extent is captured to help increase the accuracy of future storm surge forecasts.
Additionally, the Flood Control District was able to test technologies such as ARCGIS data collection uses, GPS survey equipment, and communication efforts in an area that had been heavily impacted by a major hurricane, post hurricane Laura and were able to bring these lessons learned of what worked and what did not work back to Harris County. While communication failures were extensive and widespread, the ability to conduct the high water marking effort with respect to technology generally worked well. Significant challenges were presented due to lack of water and food, widespread power outages, damaged lodging, and destroyed infrastructure making travel difficult and time consuming at times.
Team members: Jeff Lindner, Jeremy Justice, Justin Terry, Ismael Cisneros, Richard Velasco, Valerie Lomas, Dustin Jones, Jeff Lu, Felix Bonilla, Ronald Havran, Ian Shelton, and Daniel Will