Number 32, February 2002
Mitigating Severe Weather Impacts in Urban Areas
What happens when severe weather strikes a major urban area such as Houston, Texas? The answer to this question depends on your perspective. In an ideal world, strong winds would have no effect on buildings or the citys infrastructure, and flooding would pass through without damage or loss of life. This scenario is very different from what actually happens. For example, Tropical Storm Allison last year proved to be the most expensive tropical storm in U.S. history. One reason that Houston experienced $5 billion in damage is that more people and industry have moved to areas of increased risk from tropical storms and other natural hazards. Another reason is that an unusually prolonged, intense rainfall over a large spatial extent fell over urbanized watersheds, causing some of the worst flooding of any storm to hit Houston to date.
Floods are the most common natural disaster, accounting for 80% of all Presidential Disaster Declarations. However, 90% of flood disasters do not receive this declaration. Vulnerability to flooding has increased due to development in and around floodplains, increasing vulnerability of civil infrastructure to flood waters. Flood damage is estimated to cost the U.S. from $5 to $8 billion annually. We can do little to change the weather, but we can change the way communities and their supporting infrastructure are planned and designed. Better construction and planning could mean that intense rainfall or strong winds would have little impact on communities. Achieving this goal requires better education of the public, government officials, and professionals involved in the planning, design, and construction of our engineered environment.
Will we see another Tropical Storm Allison of equal or greater magnitude? Probably. Will we be better prepared? That is the desired outcome of The National Symposium on Mitigating Severe Weather Impacts in Urban Areas. The conference will be held at the Hornberger Center of the Texas Medical Center in Houston, Texas, on April 15-17, 2002. The goal of this conference is to bring together specialists in societal impacts, hydrology, meteorology, civil engineering, city planning, and related technologies to identify how to cope with the ever-increasing insured losses, damage, and loss of life that occur when severe weather strikes an urban area.
Over the last 35 years, the costs of weather-related disasters across the United States have doubled or tripled each decade. Hardening our engineered environment to meet this threat requires more research on how to build better infrastructure to withstand severe weather. Increased population and wealth places the U.S. at greater risk than ever before. Planning for flood hazards fall into three categories: 1) more accurate predictions, forecasts, and warnings, 2) improved construction standards and siting of structures in ways that minimize wind or water damage, and 3) carefully planned protocols for responses that mitigate impacts of imminent flooding.
Better methods of predicting natural hazards will help recovery plans by enabling cities to organize and mobilize relief agencies. A good disaster recovery plan also takes into account the effect of economic hardships that follow a disaster, and it includes creative ways to overcome those hardships and reestablish the vitality of the community. In the end, a natural disaster can be turned into an opportunity for communities to rebuild while reducing vulnerability. Facility redesign, improved drainage infrastructure, warning systems, and a better plan of action in the face of disaster can reduce future losses.
Examples of improved infrastructure design that prepares us for future storm events can be found in the aftermath of Tropical Storm Allison in Houston. Figure 1 shows newly installed flood doors at the Texas Medical Center (TMC) that retrofit the facility to withstand higher flood levels. Structural engineers and architects in the early phases of TMC development in the 1950s scarcely envisioned the need for designing flood doors and gates that restrict the flow of floodwaters entering tunnels and parking garages in the TMC campus. Yet this is just what is needed in light of increased development upstream and land subsidence in coastal areas such as Houston due to groundwater withdrawal. Isolation of backup electrical equipment, automatic floodgates, flood doors, and a warning system giving advance notice reduce flood damage. While waiting for the flood to arrive, measures can be taken to prevent or reduce floodwaters from entering facilities. Given advanced notice, personnel and operational logistics can be marshaled in order to continue critical medical services to the community.
New radar detection and flood warning systems can be put into place to help reduce losses. Technological advances in weather detection, warning systems, and advanced hydrologic model predictions improve the accuracy of flood warnings. Simply detecting rainfall does not indicate whether or where it will flood. Coupling of radar and distributed hydrologic models offers improved information about timing and expected flood levels. More timely and accurate predictions of severe weather together with information and decision-support systems help reduce societal impacts by providing the most useful information to stakeholders.
Planned sessions for the symposium focus on various severe weather impacts in urban areas, particularly flooding. Several keynote presentations are planned including one from John Snow, Dean of the College of Geosciences and Director of National Weather Center Programs at the University of Oklahoma, and another from the Director of the National Academy of Sciences Board of Atmospheric Sciences Committee, Joe (Elbert) Friday, Jr. (former Director of the National Weather Service). Several organizations are joining efforts to host this symposium: The International Center for Natural Hazards and Disaster Research (ICNHDR) at the University of Oklahoma, the Energy and Environmental Systems Institute, and the Department of Civil and Environmental Engineering, both at Rice University, and the Texas Medical Center.
For more information on the National Symposium, see the news item in this issue of the WeatherZine entitled Symposium on Mitigating Severe Weather Impacts In Urban Areas.