Since 1900, Texas has experienced some of the biggest flood events in recorded history resulting from hurricanes and tropical storms. Regions of Texas along the Gulf of Mexico are prone to impacts of severe storms. These storms can form within a few hours in the warm summer water and hit land with little warning and with devastating results.
Major flooding events that have ravaged the Houston area recently include Tropical Strom Allison in 2001, the 2015 Memorial Day Flood, the 2016 Tax Day Flood, and Hurricane Harvey in late August 2017, which relentlessly battered the coastal city and left major damage to the region in its destructive, unforgiving wake.
The damage caused by the Memorial Day and Tax Day floods may have been localized in size and short in duration but were intense and powerful when they struck parts of Harris County. Conversely, Tropical Strom Allison and Hurricane Harvey hit with lower intensity, but its range was widespread. Tropical Storm Allison followed an erratic path and moved slowly, while Hurricane Harvey stalled over southwest Harris County, resulting in massive flooding from both storms.
The topography of the Houston area is very flat. It is also heavily developed and populated, so infiltration of rain water is very limited. It takes only a few inches of heavy rainfall in these vulnerable regions causes the streets to flood.
In these storm events, most of the flooding occurred outside the designated Flood Insurance Study (FIS) flood hazard zone, indicating that the risk to property owners and residents in this region is widespread.
Measures such as advanced warning systems are currently in place to deal with acute and recurrent flooding in the region.
For example, the Harris County Flood Control District (HCFCD) has rain and stream gauges installed throughout the county, gathering information that can be accessed by the public on the District’s web site. From this site, visitors can observe how fast water is rising, and where it is at risk of reaching the top of the channel bank.
This information, in addition to live media updates and official statements from Central Command (Transtar), helps Harris County residents prepare better and avoid flooded area. Without these warning systems, the economic damage and loss of life would be even more dire.
Another HCFCD effort is forecasting bayou water levels a few hours ahead of time by following the Radar Track forecast to determine the most likely path the storm will follow, where it may strike and its rainfall intensity. In this scenario, a complex computer simulation evaluates past rainfall radar data and stream gage readings, and coupled with LiDAR topography information, forecasts the level of potential inundation. The forecasting system results can be updated every 15 minutes.
It’s important to note, however, that this particular forecasting system is in its infancy and will require more testing and adjustments to improve its reliability.
Focused on Mitigation
While forecasts to alert the community about pending hazards and risks are critical and often lifesaving, the focus now is turning to expedite the implementation of mitigation projects that have been in the pipeline for years. When completed, the mitigation will hopefully reduce the need for such dire alerts to be issued.
One measure being explored now involves improvements to the flood-carrying capacity of the bayou by diverting the floodwater into underground tunnels. Also, improvements to the conveyance of the existing channels could also contain the flow within the banks of the bayou. However, these measure takes time to implement and require substantial financial investment and coordination.
HCFCD has been implementing a program for undeveloped watersheds, located mainly in the northwestern part of the Harris County, in an area known as the Little Cypress Creek Watershed. The program is aimed at constructing channel conveyances and other infrastructures before development occurs and acquires the necessary right-of-way needed to construct flood mitigation facilities.
After Hurricane Harvey, Harris County implemented new development regulations, and expedited the buyout of properties that experienced repetitive flood damage. Properties purchased in these areas will be used for flood mitigation.
With storm severity and frequency on the rise, it is critical to look beyond traditional approaches, elevate these measures further, add more alternatives to the flood preparation “tool box”, improve design capacity and perform rigorous analyses of the proposed system in a holistic manner before any construction begins.
There also must be close cooperation between entities to improve and increase the level of service the flood conveyance system can provide. Flood water does not follow jurisdictional boundaries; it flows from higher elevation to lower elevation, and the bayou in the region crisscrosses several boundaries before outfall into the Gulf of Mexico.
Cooperation and expedited decision-making are critical to prepare the region for the next big storm.
Before Hurricane Harvey, investment in flood mitigation was minimal, apart from a few Federal Flood Reduction and FEMA grant-funded projects. Lack of funding hampered speedy implementation of most flood mitigation projects.
Since 2018, the financing situation has improved. Harris County has adopted a bond program specifically for flood mitigation projects, and the Federal government has expedited funding and projects that were on the shelf for years, such as the Clear Creek Federal Flood Mitigation project.
In addition, the State of Texas has funded a resiliency program project, property buyouts in chronically flooded areas, and other neighborhood improvement programs. While no single project will solve the flooding problem overnight, these efforts combined are improving the situation, and with further study, investment and action, the region should be more equipped to minimize, prevent and overcome the impacts of these brutal storms.
With the capacity, resources and expertise in multiple areas to help municipalities and other entities address chronic flooding situations, WSP is bringing its international and national talent together to deliver local, area-specific solutions in Texas and other areas where flooding is an ongoing issue.
A view of an impassable, submerged roads caused by Hurricane Harvey in August 2017, as seen from Eldridge, Texas (west of Houston) looking north.
Combining Local and Technical Knowledge
WSP provides system modeling and analyses of alternatives, design of facilities, construction and program management, and public outreach to explain the drivers and objectives of these projects, and how they will benefit in the long term through this level of protection. Through its Future ReadyTM lens, WSP can provide local officials and agencies with valuable insights that will address long-term issues while tackling present and persistent problems.
WSP has developed innovations and tools, being used in various regions of the country facing similar conditions and challenges, that will expedite the work. These are innovations that will not only help the Houston area, but could easily be adapted to fit or address other Texas environs where flooding is problematic.
It gives me tremendous satisfaction to have this opportunity to present solutions that will help pave the way to improve the mitigation of flooding in my community and other areas in the Region. When these projects are implemented and flooding is minimized or eliminated, the reward will be great. I look forward to living in a community that gradually becomes less worried about flooding.