May 2011

The Slow and the Sudden

A big part of stormwater management is, and has always been, flood control. Long before we had stringent water-quality requirements in place, just about every community had someone who dealt with water quantity, from the designers and planners and zoning officials to the public works employees who cleaned out the clogged storm drains.

Most flooding, of course, depends on the weather; we plan and design for the two-year, the 10-year, the 100-year storm. Many places are prepared to deal with extreme weather—cities along the Gulf Coast are always aware that this could be the season a Category 5 hurricane makes landfall, for example.

In March, we witnessed the devastation from one of the few types of flooding not caused by the weather. As we watched the effects of the tsunami on northeastern Japan, many of us on the West Coast of the US and Canada—and especially those on islands in the Pacific—waited uneasily to see what effect, if any, the 9.0 earthquake would produce on our shores.

Tsunamis are sudden and, fortunately, rare. But there is another potential for flood damage that doesn’t result from storm events, though in a complex way it has a great deal to do with stormwater management and long-term planning and investment. This is the sea level rise that some low-lying areas are already experiencing and that others are now forming strategies to cope with. The StormCon conference in Anaheim, CA, this August, will have new component on this topic: a one-day program called “Preparing for the Rising Tide: Coastal Protection Symposium,” focusing on safeguarding infrastructure in coastal cities, ports, and industrial complexes against sea level rise and shoreline changes.

These, of course, are slow processes, and on the face of it they might seem to have little to do with something as sudden as a tsunami. Many of the presentations, though, will focus on assessing coastal risks, on mapping and modeling, and on large-scale BMPs to protect against flooding. It’s the almost unnoticeably slow processes like coastal erosion, loss of coastal wetlands and transition zones, and sea level rise that make coastal areas more vulnerable during extraordinary events like hurricanes or tsunamis. As many have pointed out, here and elsewhere, what we used to consider the “100-year storm” seems to be occurring more frequently. How we deal with the slow, incremental changes will affect how we fare during the larger, more sudden ones.

You can find more information on the Coastal Protection Symposium at www.stormcon.com.