Creating more resilient floodplains

One Texas county in the heart of ‘flash flood alley’ addressed water infrastructure vulnerabilities by taking a proactive approach to flood control planning.

By Bobby Mengden, P.E., CFM

Water knows no boundaries. Yet the manner in which our government agencies, water management districts, and local communities are organized is determined by municipal and geographical boundaries. Faced with this challenge, agency, municipality, and community leaders are increasingly asking: Instead of trying to manage flooding based on municipal or geographical lines, what if we looked at it from a watershed perspective? In Bexar County, located in south-central Texas, including the city of San Antonio, they did just this, looking beyond city and political boundaries to implement a flood control program that would offer protections for not only the county but potentially the larger region.

Following two historic and devastating floods in 1998 and 2002, Bexar County, along with the San Antonio River Authority (SARA), the City of San Antonio, and 20 additional suburban cities, formed a partnership called the Bexar Regional Watershed Management (BRWM) so they could more effectively manage the floodplain and mitigate future flooding risks. As a result of this partnership, in 2007 the Bexar County Commissioners Court established the Bexar County Flood Control Program, a 10-year, $500 million capital improvement program. This program included 83 projects deemed vital to safeguarding citizens and property during significant rainfall and other weather events. AECOM was selected to manage the flood control program.

One of the major benefits of this program was that it created opportunities for all stakeholders to experience improved utility and stormwater management and achieve overall cost savings and efficiency in project design, construction, and delivery. Consistent with a program of this magnitude and complexity, the BRWM and our AECOM team overcame five main obstacles to successfully deliver projects on time and on budget that also maximized the benefit to the community.

Staffing for a finite 10-year period

With many projects to be delivered within the contract period, careful consideration was given to staffing a program of this size and nature. Bexar County supplemented its personnel using program management and staff augmentation services so team size could be adjusted based on specific staffing needs throughout the duration of this program. During early planning stages this was achieved by using program management professionals from AECOM and our subconsultants to assist in project identification, professional services contract creation, and selection of consulting engineering firms for detailed design.

Once detailed design of the projects was underway and construction had started, AECOM’s program team moved into Bexar County offices so our staff augmentation services were more closely aligned with county personnel and functioning as a true team. The roles of the team and necessary expertise fluctuated based on the life cycles of the projects. For example, initially we used design engineers to manage project designs and then transitioned to construction managers to oversee construction.

Prioritizing projects

The BRWM used a review process to identify the most critical projects based on key flood impact criteria, rather than along municipal or geographical boundaries. As part of the review process, the Water Technical Committee (WTC) was formed. This committee comprised subject matter experts from the City of San Antonio, Bexar County, SARA, and our AECOM program management team and rated potential projects by using criteria that gave higher ranking to projects that maximized public safety and hydraulic impact.

For example, projects that removed homes from the 100-year floodplain or took a highly traversed roadway out of the floodplain received higher scores. Other important considerations were considered such as water quality improvements and possible integration with other, concurrent capital improvement projects that were planned for the various municipalities. This scoring methodology allowed the WTC to prioritize projects that would create the greatest positive impact for the community.

Measuring project feasibility

The Federal Emergency Management Agency (FEMA) creates flood map products using GIS technology. One of FEMA’s products is the Digital Flood Insurance Rate Map (DFIRM). There are instances when improved digital modeling can transform the footprint of 100-year floodplains and alter the rate map without having to perform construction-related activities, which in turn can allow project teams to redirect money elsewhere for greater impacts or improvements.

On this program, there were also times when obstacles were discovered during initial design that caused a project to become unfeasible for financial or constructability reasons. To ensure stakeholders understood why certain projects were recommended for construction and others were not, the team applied DFIRM data and developed additional metrics to measure the overall benefits of each project. These metrics included traffic volume over low-water crossings; unflooded access for isolated neighborhoods or schools, homes, and businesses removed from the floodplain; upstream and downstream impacts; total project costs; and constructability considerations.

Obtaining community support

Public support is critical for moving any program or project forward. But in this case, it was especially important because there were misconceptions around the causes of flooding, floodplain boundaries, and flood control projects. To alleviate confusion and educate the community about flood safety, the team developed a comprehensive approach to public outreach that included a robust suite of communication tools. One such tool was creating a website dedicated to each project that allowed the public to check real-time project status, learn how to prepare for impacts due to construction, and provide their feedback and voice any concerns.

Improving quality of life

Although flood control projects were primarily developed to prevent flooding and provide safe mobility, many communities requested additional benefits such as enhanced ecosystems and recreational amenities. With this in mind, the BRWM and AECOM partnered with stakeholders from the different communities to identify areas where the quality of life could be further enhanced. Projects requested by citizens included hike and bike trails, parks, and soccer fields.

In addition to these amenities, the environment was protected through the team’s approach to flood conveyance, which involved using natural channel design and stream restoration that enhanced the water quality of nearby streams. Bexar County worked closely with other municipalities and private organizations to incorporate cost-sharing techniques so these amenities could be combined with the program’s flood control aspects.

Successful completion of this 10-year program resulted in 83 total projects, including 63 improved low-water crossings, 10-plus miles of channel improvements, eight dam improvement projects, 1,648 homes removed from the floodplain, and 142 high-water alert technology (HALT) sites installed throughout the region. Bexar County’s commitment to deliver and invest in this program also boosted the local economy, which at the time of inception was experiencing a downturn. More than 4,700 jobs associated with the program were created, enhancing the community’s economic condition and bringing increased value for homeowners and taxpayers.

This overall program achieved successful outcomes because AECOM and Bexar County were aligned and focused from the onset on our ultimate priorities — efficiently staffing the program based on project life cycle, creating tangible project scoring criteria that examined flooding criteria and other important social factors for prioritization, examining project feasibility to properly allocate program funding, receiving input from the community throughout the process, and including additional project features to enhance this program for all communities. By working together, we delivered a flood control program that will benefit the region for generations.

Bobby Mengden, P.E., CFM, is a project manager, water, in AECOM’s Central Region (www.aecom.com).