Understanding Flood Warning Systems: tools, timelines, and impact

Devastating floods hit Texas this summer, resulting in loss of life, lasting property damage, and shattered families and communities. Understandably, preparing for the next flood has taken on renewed urgency for local governments.

Many localities are taking on this task during their annual budgeting session. “City staff and council members are reaching out to local experts, asking what it would take to get an early flood warning system in their city,” says Zubin Sukheswalla, P.E., CFM, Senior Vice President at Pape-Dawson. For years, Pape-Dawson’s Hydrology & Hydraulics practice has guided entities through their options. “We help them understand what that endeavor really means with regard to cost, the amount of effort, and how long it will take before they see true early flood warning benefits.” A key point he emphasizes to clients is that it can take years to get from flood monitoring (knowing real-time flooding depths by location) to flood warning (predicting impending flooding emergencies and alerting officials and citizens so they can act).

The process for implementing an early flood warning system starts with defining the client’s needs and surveying the elevations of roadways and critical points of the river, creek, or stream bed. After that, Zubin’s team leads clients through decisions on:

• Aligning the community’s short-term needs with long-term priorities. A community’s short-term and long-term vision, combined with topological constraints, will inform the choice of sensors and communication systems that can be scaled smartly over time. For instance, communities should prioritize rain gages in critical areas, as well as plan for redundant power and communication systems in case of power interruption.
• Selecting appropriate solutions. There are various approaches, such as a simple rating curve or a real-time model, to predict imminent flooding conditions. Decision makers ought to consider the pros and cons of each to optimize their system according to their expectations and budget.
• Getting the word out. Once the software forecasts a likely flooding event, how will the right people find out? “Most cities and counties have a website with a more general view for citizens and outside agencies. Then there’s a separate stakeholder view with the ability to dig deeper into the details the experts need,” says Zubin.  How you communicate flood-risk alerts can be as critical as the prediction itself.

“Getting that data measurement, analysis, and communications infrastructure in place and tested so we feel confident in it takes several years on average,” Zubin says. “And that gets us only to flood monitoring, not yet to flood warning.” In fact, it could take five to ten years of data collection to train models that can reliably forecast flooding events. Unrealistic expectations can be dangerous. “If a flood hits after millions of dollars of bond funding have been spent, but we haven’t collected enough data for prediction yet, the city manager or council members need to be able to explain to the public why the flood warning program isn’t a failure.”

“We also have to set standards for whom we’re going to notify, and how they will get notified,” adds Vice President Jake Powell, P.E., CFM. Early on, crews will start barricading low water crossings, and local officials will track conditions and implement appropriate countermeasures. Because false alarms degrade public confidence, residents will get an alert at a higher threshold when flooding is deemed more likely. “A system with pre-established communication triggers and timely human intervention is key to a system that protects the public and maintains its trust,” says Zubin.

After the process of planning, hardware and software setup, and data collection, the result is a system that notifies local officials and residents with enough lead time to save lives. With regard to funding, now may be the best time in recent years to start the process, says Client Services Manager Bobby Mengden, P.E. “Since the summer’s flood events, we’re seeing a renewed state focus on flood warning. Cities and counties may not have had the ability to do this early flood warning work themselves with local budgets, but they may get more assistance from the state going forward.”

That means they will need qualified, experienced engineers to implement those solutions. “In every major landscape in Texas, we’re guiding
municipalities toward their long-term goal of flood warning,” says Jake. Across Texas and beyond, Pape-Dawson is ready to help.