Written By David E. Winslow, P.E., LJA Engineering & Surveying, Inc.
If the Allen Brothers could return to Houston today, more than 160 years after their first arrival, it's likely that they would be astounded by what they would see. From Houston's humble beginnings along Buffalo Bayou, their dream of "a great center of government and commerce" has certainly been achieved many times over. Besides the obvious changes with the skyline, freeways and millions of people, the brothers would be taken aback by how much drier and livable the City has become.
Early Development
How did Houston and the surrounding area get to the point it's at today?
As Houston began to grow, the builders of the City first focused on the pressing day-to-day needs such as building roads for transportation. The first significant drainage projects were also really transportation related, with the dredging of Buffalo Bayou beginning in the 1850's and reaching a 25-foot depth by 1914.
In the early 1900's, the U.S. Geological Survey began an ambitious effort to prepare detailed topographic maps of all of Harris County. These maps represent drainage patterns untouched by the settlers of Houston. The maps show that with the exception of the major bayous there were few if any tributary channels providing drainage of the undeveloped land.
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Detention and Recreation Facility at Arthur Storey Park in West Houston - © Harris County Flood Control District. Reprinted with permission. |
As Houston continued to grow it became necessary to construct the needed tributary channels to drain the streets and subdivisions that began to spring up in the early 1900's. During this period, numerous floods were documented in the local newspapers. In 1935, the worst flood that the City had suffered to date inundated sections of downtown Houston. The extensive damage spurred the creation of the Harris County Flood Control District (HCFCD) in 1937.
Flood Control Authorities
The HCFCD began to embark on a series of ambitious flood control projects. In cooperation with the U.S. Army Corps of Engineers, Barker and Addicks Reservoirs were constructed in the late 1940's in west Harris County and part of Fort Bend County. These two reservoirs were the first and largest flood control detention facilities in the County, providing a combined 400,000 acre-feet of flood storage.
Meanwhile, the focus of the HCFCD's efforts was the construction of a series of major channels over approximately a 30-year period from the 1940's to the late 1970's. By the end of this period, HCFCD operated over 2,500 miles of improved channels.
Flood Control Monitoring
An important part of the flood control effort has been the collection of rainfall and flood flow data. Beginning in 1936 with Brays, Buffalo and White Oak Bayous stream flow stations, the U.S. Geological Survey has continuously collected rainfall flow and flood elevation data in the Houston area for over 65 years. In the 1980's the HCFCD significantly expanded the number of streamflow stations. The rainfall and flow data has been analyzed at various times to understand the impact of the built environment and has contributed to the evolution of design criteria that considers that impact. In 1972, the USGS published a study by Steve Johnson and Doug Sayre which concluded that the built environment and the channel improvements could significantly increase the flow downstream. This study and others caused HCFCD and other agencies to revise design criteria and to reassess the overall approach to flood control.
Flood Insurance Program & Detention Requirements
Another significant event that drastically changed the flood control approach was the establishment of what is now the Federal Emergency Management Agency. FEMA was created in 1973 to establish a subsidized flood insurance program and related controls on development in areas subject to flooding. The program required new development to be protected from stream flooding up to the 100-year (1% probability) level. The program also required cities and counties to control and reduce floodplain development and to prevent increases in flooding due to new construction. Regional detention basin sites were bought by HCFCD in some watersheds. New developments were required to make cash contributions to HCFCD to provide storage in these basins or provide individual on-site detention facilities to control peak flows to prior development levels.
NEPA & Environmental Policies
The National Environmental Policy Act of 1969 and subsequent amendments require environmental impact studies for many flood control projects, and scrutiny from the public and environmental agencies. More recently, the recognition that development can also cause significant degradation of water quality has brought about the Federal Clean Water Act controls on routine rainfall-runoff events to prevent sedimentation, erosion, and other water quality degradation. In many cases detention basins are now designed to store the first portion of a typical non-flood producing rainfall.
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Hike & Bike Trail along Brays Bayou -
© 2002 Harris County Flood Control District. Reprinted with permission. |
Recreation Needs
Another aspect of flood control that is becoming increasingly more important involves the consideration of these facilities as long-term community assets. With the long linear corridors created by the channel systems and the creation of adjacent large open areas for detention, flood control agencies realize that the recreational needs of the community can often be integrated into the flood control system. Numerous examples exist in and around Houston of channels that provide jogging and bike paths, and of detention basins that provide active and passive recreation. Some of the major bayou systems are now being developed as commuter bikeways.
The Future of Flood Control
So we've seen the process of controlling floods evolve from what was first thought to be a simple task of getting the water to the major bayous, to what is now a complex system of channels and detention basins that may have recreation facilities, wetlands, and water quality features.
In many cases the process now involves multiple partnerships, including HCFCD, the U.S. Army Corps of Engineers, local municipalities, utility districts, neighborhood associations and environmental groups, the Texas Department of Transportation, and state environmental agencies.
We see a proactive process evolving which recognizes the need for drainage and detention facilities to serve as multi-purpose assets reflecting a combination of differing needs and desires of the community. The systems are constructed to respect the existing natural environment, particularly in newly developing areas, while addressing human needs as well, particularly in the more urbanized areas. Channels may have a more structural, yet visually attractive look that reflects the area's character while addressing the necessary flood control for a more dense urban area.
The facilities we are planning and building today, will be used by many generations to come. The public needs facilities that will age well and grow in value to the future users.
