River and Flash Flooding Session 2 Abstracts (Friday)

4:45pm - 5:00 pm // The use of Dual Polarization Radar Precipitation Products during a Small Scale Urban Flash Flood // Lance Wood // NWS Houston-Galveston
    During the evening hours of May 12th 2015, slow moving thunderstorms over southeast Harris County became nearly stationary and produced 6 to 12 inches of rainfall in 3 hours. This heavy rainfall occurred over a small area (25 square miles) near NASA in Clear Lake, TX. The result was a rapidly developing major flood across an urban area. Numerous vehicles became stranded in deep flowing water along several major roadways with numerous high water rescues. One flash flood vehicle fatality occurred when a car was washed off of a highway and into a flooded drainage ditch. Although real time rainfall gauges are located across this area as part of the Harris County Flood Control District’s rainfall gauge network, the closest gauge missed the heaviest rainfall, recording 6.2 inches in 3 hours which is approximately half of the maximum occurring only a few miles away (11.98 inches from a NASA employee’s home weather station). Instantaneous, hourly, and storm total dual polarization precipitation estimates were accurate, and proved to be critical in providing timely flash flood warnings for this small, severely impacted urban area. This presentation will highlight the value of these products during a rapidly developing, small scale flash flood event.

5:00pm - 5:15 pm // An Operational Radar-based Flood Warning System with its Performance Evaluation for the 2015 May 26 Event in Houston, Texas // Nick Fang // 
UT-Arlington
    As non-structural tools, radar-based flood warning systems can provide accurate and timely warnings to the public and private entities in urban areas that are prone to flash floods. The wider spatial and temporal coverage from radar increases flood warning lead-time when compared to rain and stream gages alone. Thus the radar-based flood warning systems have become more prevalent in the past decade to provide the information necessary to mobilize the evacuation of people and property prior to flooding in critical areas
    This paper will present an operational radar-based flood alert system for the highly urbanized Rice University and the Texas Medical Center (TMC) areas in Houston, Texas. This radar-based Flood Alert System (FAS) has been providing important warning information for the critical medical facilities for more than 50 events since 1997. The system utilizes NEXRAD Level II radar rainfall data coupled with a real-time hydrologic model (RTHEC-1) to deliver warning information with 2 to 3 hours of lead time and a forecast R2 value of 93% to facility personnel in readily understood format. A user-friendly dashboard enables users to visualize rainfall maps, Google Maps based inundation maps, hydrologic predictions, and real-time monitoring at the bayou. This paper will discuss the evaluation of its reliable performance during the recent events occurring from 2012 to 2015. Due to its excellent performance, Texas Medical Center has included FAS3 into their FEMA Success Story as a good example to demonstrate the significant value of the radar-based flood warning system. The paper will also demonstrate its excellent flood prediction performance for the May 26 event in 2015. Having a significant role in the communication of flood information, FAS marks an important step towards the establishment of an operational and reliable flood warning system for flood-prone urban areas.

5:15pm - 5:30 pm // Comparing the Two Major Red River Flood Events of 2015 at Pecan Point // Cynthia Palmer // NWS Shreveport
    Two major floods developed along the Red River at Pecan Point in 2015. The first flood occurred during the late spring and early summer, following a series of heavy rain events that brought unprecedented and record rainfall to the Red River Basin of Southern Oklahoma and Northern Texas. A wide swath of the basin recorded 20 inches of rainfall or more in May, leading to major flooding along the Red River and flooding thousands of acres of farm and pasture land in Red River and Bowie Counties. Interstate travel was impacted as well, as the US Highways 259, 8, and 71 bridges over the Red River closed. Pecan Point recorded its third highest crest and the first major flood in nearly 25 years. The second flood event is ongoing, with the Red River forecast to crest at Pecan Point within the next 24 hour. Over the past four days (beginning on Thanksgiving), rainfall totals downstream of Lake Texoma ranged from 8 to 12 inches, with rapid rises once again occurring along the Red River as well as the Sulphur and Sabine Rivers in Northeast Texas. This study will examine the rain events leading in these two flood events as well as floods themselves.

5:30pm - 5:45 pm // Becoming E.F. Hutton: How Partnerships Among NWS Brownsville, Corpus Christi, and South Texas Emergency Managers Prepared Communities Prior to Flooding in 2015 // Barry Goldsmith // NWS Brownsville
    2015 brought numerous heavy rainfall events to South Texas and the Rio Grande Valley region along the Texas/Mexico border. Several of the events produced significant flooding to communities across the region. These communities included urban centers of Edinburg, Weslaco, Brownsville, Alice, and Corpus Christi; rural farm communities in Willacy, Duval, Jim Wells, and Nueces County; and unincorporated neighborhoods (“colonias”), mainly in Hidalgo County. Events included May 11-13 and June 17-19 (all areas); August 31st and October 30th (Brownsville), and October 22 (Willacyh), and October 23-25 (all areas). Hidalgo, Nueces, Jim Wells, and Duval Counties were included in the spring 2015 Federal Disaster Declaration, and Hidalgo and Willacy were included in a Texas Disaster Declaration following the October 22-24 floods. Property losses and agriculture damages will likely be more than $250 million.
    Emergency Management (EM) prepared for these events by staging physical resources and deploying human resources, largely based on decision support from the National Weather Service (NWS) in Brownsville and Corpus Christi. The decision support ranged from pre-event e-mail “blogs” and occasional webinars, shared with more than a thousand users in nearly every Emergency Support Function, to individual phone calls between office staff and first-line Emergency Management Coordinators. This presentation will describe specific actions taken by decision makers across South Texas and the Rio Grande Valley to increase EM readiness prior to the floods. The actions, based on effective communication of the hazard/threat, potential impact, and suggested action by the NWS, improved rapid response and ensured the safety of impacted populations once flooding began.