The inundation of California with rain and snow over the last several months has brought multiple stormwater realities and concerns to the surface. In addition to damaging floods, the threat of future challenges remains as winter’s snow begins to melt. Combined with the recent drought, California finds itself in a real water management quandary. While California has emerged as the poster child for what needs to happen next in the stormwater industry, they are by no means an anomaly. As the climate continues to change, states, cities, and towns across the U.S. will be faced with water challenges. The solution? Education, proper product selection, and planning. Challenge Overview In 1972, the Clean Water Act, a national regulation, instructed that stormwater must be treated. California then created its own regulations—as did many states—that are implemented today by state water boards dictating how stormwater is to be treated to be sure any pollution is disposed of properly. This helps with the limiting of erosion, flood mitigation, and much more. Let’s take a closer observation at what happened—and is still happening—in California. When looking at the immense amounts of rain that have fallen in 2023 in California—30.04 inches as of April 9 representing 148 percent of average, according to California Water Watch—the root of the problem is that the sheer volume of water has overwhelmed existing infrastructure. The built environment—typically urban, very developed areas—is not equipped to handle this volume of water, and the natural water cycle is being disrupted by the amount of impervious surfaces in urban environments. This means water can’t infiltrate the ground as it once did, overwhelming current management infrastructure and increasing flood risk. This water is bringing with it more sediment, which creates pollution and safety hazards. The current infrastructure in place cannot handle the amount of water it’s receiving which is causing severe safety impacts—flooding and more—to the population. “While the situation can seem overwhelming, there are ways that exist to manage these situations, to target flood-risk areas quickly” said Laraine Sanfilippo, commercial operations director for Oldcastle Infrastructure, a CRH company. “What we’re learning on a very real- time basis is that stormwater must be captured and infiltrated on-site as much as possible. In a nutshell: what was once ‘how fast can we get the water to the ocean’ is now ‘has fast can we capture it.’” When it comes to the big and infrequent rainstorms experienced by Californians, it’s all about capturing as much water as possible when the opportunities arise. Just out of a long drought, it’s safe to assume that the next couple of years could be dry for California. Storms and atmospheric rivers provide the perfect opportunity to Stormwater/flood response By Matika Made
The installation of an Oldcastle StormCapture® system. This underground vault connected to drywells will hold the rain from a typical storm and allow it to infiltrate deep below the urban landscape.
capture stormwater and save it for years down the road. But are these opportunities being maximized? Statewide snowpack levels, as of April 9, are at 238 percent of average. Snowpacks are one of the world’s largest water detention systems and a big part of the California water system as the snow melts and feeds reservoirs and rivers. But with snowpacks at shockingly high levels, the concern is valid that a rapid warm-up in the spring could result in even more flooding. “At the heart of the issue is the connection between our natural environment and the built environment,” said Tyler Metcalf, general manager of Torrent Resources, part of Oldcastle Infrastructure, a CRH company. “Episodic droughts historically have caused aboveground resources to be visually depleted; now, with recent rains, our reservoirs, rivers, and streams are full of water, giving the perception on the surface that we are no longer experiencing the effects of prior drought and water supply is at capacity—but that’s not the case. In reality, we have overdrawn groundwater for years and we must replenish our depleted aquifers to ensure one of our world’s most valuable resources, water, is available for future generations.” The historic practice of Flood-MAR (flood-managed aquifer recharge) is one method to lessen the impact on the built environment by flooding agricultural land to help alleviate flooding downstream and keep water where it lands for more effective infiltration. Given that agricultural lands are the biggest users of water coming out of aquifers, this makes sense. But forethought is necessary: variances must be obtained in order to flood agricultural lands; by the time the rains arrive, it’s too late to submit a request. Studies are in process throughout the U.S. to evaluate the effectiveness of this method compared to newer technologies that can more effectively infiltrate stormwater and recharge underground aquifers for future widespread use. Results of these studies are expected in the coming months. At the end of the day, California—and especially Los Angeles—have made significant infrastructure moves and are ahead of the curve when it comes to stormwater management. But what more can be done to better prepare for and capture the water from the growing number of large storms the state and the country are experiencing?
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csengineermag.com
June 2023
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