Flood Control: Confronting a Houston Reality
By Jung Jang
When I first moved to Houston back in June of 2001, I remember seeing water everywhere from above while flying back from my honeymoon. Tropical Storm Allison had just unleashed torrential rainfall on Houston. The shock and the gravity of flooding was instilled in my heart as I started my career as a hydrologist. The recent historic flooding just re-affirmed the major issues that the City of Houston and its surrounding counties face with aging infrastructure and lack of public information regarding the dangers of high water.
Even without an unprecedented storm, the City of Houston and its surrounding areas are known to be subject to frequent flooding, which is not surprising since Houston’s climate is categorized as humid subtropical. Seemingly different areas in the Houston region undergo flooding every year. Flooding issues are not isolated to areas designated as a 100-year floodplain. Areas that are not in the 100-year floodplain can also be affected by storm water, as we have seen this spring and when Tropical Storm Allison hit in the summer of 2001. That is why I always recommend to friends and family to obtain flood insurance. The 100-year floodplain only covers flooding due to the overflow of bayous and channels, not your localized drainage systems that convey the water from your streets to the bayous and channels.
Most everyone who has lived in this area for more than a few years has experienced some level of flooding, if not in their homes, then in their streets. There are several reasons for this. One has been provided by nature, and the network of bayous is not the only culprit. The region has nonporous soils that repel heavy rainfall, plus flat terrain that impedes the flow of water.
The problem has been exacerbated by the area’s fast-paced growth, resulting in higher runoff volumes due to the decrease in natural ground that permeates rainfall events. Sometime, it doesn’t take much of a storm to cause problems. Anything more than one inch per hour of heavy, intense rain can result in street flooding.
Flooding of existing neighborhoods – caused by poorly constructed or antiquated pipes being unable to handle heavy rains – is well-known and is one reason the City of Houston voted itself a drainage fee a few years back. And new housing is subject to flooding problems as well, and every new project needs to have detention mitigation as part of its planning, as well floodplain mitigation if the development is located within the regulatory floodplain.
This may add to the cost of developing new property, but it’s important to consider that property with the potential for flooding will not be marketable in the future. It can be a question of do it now, or do it later by retrofitting the property – a more expensive proposition.
There are other factors to consider in these cases. For instance, the flow of water will be affected by the ratio of grass to concrete, since concrete can impede natural drainage. If the area is unstable, an engineer may recommend a detention basin. However, detention basins reduce the amount of land that can be developed into lots, so developers are often reluctant to include them.
Providing detention basins or floodplain mitigation measures are very essential to all development within the Houston region. However, this mitigation infrastructure can be built to improve the quality of the life for residents that live around it. For example, detention basins can be built as amenities, for use as soccer fields or playgrounds for times when it is not holding water. There is also a growing interest in green infrastructure, where drainage is integrated into the natural environment with creeks, paths and indigenous plants taking the place of concrete pipes. This kind of drainage can actually enhance the appearance of the property.
The three counties that make up the bulk of the greater Houston metropolitan area have a great deal to offer in terms of the natural environment and accessibility to work and shopping. The time and money it takes to mitigate flooding – however it is done – can pay off for everyone in the long run.
Jung Jang, P.E., C.F.M., is a Senior Project Manager and Storm Water Specialist at R. G. Miller Engineers, Inc.