Flood Inundation Mapping Impact on the Decision Making Process for Emergency Managers

The three year period from 2015 through 2017 has brought significant flooding events to Texas setting record flood levels in areas over much of the state, including widespread catastrophic flooding from Hurricane Harvey in 2017. Post-event assessments from these record flood events revealed that the top request from the emergency management community is access to flood inundation mapping during a flood event. The response by the Department of Commerce was the issuance of an Agency Program Goal (APG) to improve flood related decision support services by demonstrating a new flood inundation mapping capability to local, state, and federal emergency management for all of Texas by September of 2019.

To answer this request, the National Weather Service in conjunction with other federal, state, and local partners developed a series of exercises to examine and quantify the impacts to decisions emergency managers make if forecast flood inundation mapping were available. These exercises placed both local and state emergency managers back into previous significant flood events and analyzed the decisions that were made during the actual event against the potential decisions and response that were made during the simulation with inundation maps.

The responses acquired during these exercises will display how these inundation maps may be utilized to advance the development and implementation of inundation mapping as its ability continues to progress in Texas. One example was the requirement of depth in available inundation mapping as the critical depths of 30” of water distinguishes whether high water rescues could be performed by high profile vehicles, or if boats and helicopters are required. Understanding these thresholds and other decisions that are made in flood response by including emergency managers in the development phase makes the entire process more efficient in creating a product tailored to the end user.