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Some Agencies Are Ill-Equipped for Stormwater Issues

With the impacts from climate change, in some areas there is now a higher concentration of rain in a shorter period of time and stormwater systems, typically in the West and Northeast, are being overwhelmed.

In what amounts to a perfect storm of aging water and flood infrastructure combined with more intense rainfall in certain parts of the country brought on by climate change, a number of agencies around the country are ill-equipped to handle the new normal of heavy rainfall events.

A survey by AEM, a weather-monitoring software company, showed that just 35 percent of municipal stormwater managers feel their systems are ready for severe storms. And just 26 percent said their budgets could meet the increasing needs of the challenges posed by climate change.

That is but a confirmation of what weather experts and emergency managers already knew — that in some parts of the country, climate change is intensifying rainfall events and posing a risk to aging infrastructure and risking lives and property in the process.

“What we were looking for from the survey was an understanding of how the infrastructure is to deal with more intense storms,” said James Logan, water market leader at AEM. “The stormwater systems that are out there were typically designed for storm events that were more typical 30 or 40 years ago when they were designed.”

Today, with the impacts from climate change, in some areas there is a higher concentration of rain in a shorter period of time and those systems, typically in the West and Northeast, are being overwhelmed.

The solutions involve first understanding what’s happening and where, and gaining the knowledge of what the new normal is and measuring that against existing infrastructure to understand if the infrastructure will stand up to it.

Typically, once there is an understanding of the problem, software modeling can provide a solution by predicting where trouble spots in the infrastructure are going to be during a storm and notifying personnel.

For example, Sacramento County, Calif., has a multitude of levees to deal with, along with flows coming from the Sierras that run off into the rivers toward the San Francisco Bay, providing multiple locations and opportunity for catastrophic flooding. In response, sensors are strategically placed throughout the area to provide data on flood stages and where flooding may occur.

In Sonoma County, Calif., wildfires removed the vegetation that would have absorbed runoff and slowed down potential flooding. In response, the county had to upgrade a flood monitoring system that was unable to handle the new onslaught of water and would become overwhelmed.

Carlos Diaz, hydrologist and deputy director of engineering for Sonoma County Water Agency, said with the old system the flash flooding would trigger the gauges to send information at the same time and “you’d get data collisions and losses.” The new system captures and transmits “incredibly small packets of data,” and the alerts will transmit at the same time.

In Santa Barbara County, Calif., within a span of about five miles the terrain increases in steepness from sea level to about 3,500 feet. During high-intensity storms, the steepness results in rapid discharge and an increased probability of flash flooding, which carries with it substantial amounts of debris that can clog critical choke points. For the county, the solution is a network of field cameras and a public-facing website for real-time situational awareness, along with data that is monitored by AEM sensors.

Logan said most of the systems are provided for emergency managers to use for response and not for the public.

“If it rains really hard in an area and the water gets concentrated in the catchment areas, those are the places where flash flooding occurs, and the systems are designed to provide a warning to emergency managers.”


Jim McKay is the editor of Emergency Management magazine.