Is Building in Floodplains a Good Idea?

Floodplain development is contributing to the demise of Puget Sound orcas. Photo: Minette Layne/WikiMedia Commons
“Where will we put the next million people moving to Puget Sound?” I was asked this question recently by a business lobbyist concerned that new floodplain protection requirements would make building in flood-prone areas more difficult. His question was driven by projections that the region’s population is projected to grow by 30% in the next 30 years. But his question also suggested that floodplains are a good place to construct new homes and businesses. Well, are they?

The Costs of Flooding

Since 1990, Puget Sound has been ravaged by 15 major flood disasters—that’s more than one every other year. As outlined in our new report, Changing Course: Why Protecting Floodplains is Good for People and Wildlife, thousands of homes have been damaged or destroyed and at least 58 people have died due to flooding. These floods cost taxpayers more than $1.37 billion in clean up and recovery costs.

Humans are not the only ones affected by floodplain development. Since 1900, Puget Sound Chinook salmon populations have declined 93% and nine runs of Chinook have gone extinct. Orca whales, which eat primarily salmon, have declined by half. Both are now under federal protection through the Endangered Species Act, but habitat and populations continue to decline.

Developing in Floodplains

Tolt River Road near Carnation, WA inundated by floodwaters. Photo: King County.
Floods are a natural occurrence, but flood damage needn’t be. One of the reasons Puget Sound experiences so much damage from flooding is that we’ve put so many people and buildings in harm’s way. More than 100,000 homes and business have been built in floodplains in this region.

By filling floodplains and leveeing rivers, we’ve diminished the ability of the land to absorb large storms. More than 90% of our floodplains and wetlands have been lost to development, agriculture and other human activities. Of the floodplains that remain, more than 70% are in poor condition. The result is an increase in devastating flood damage, degradation of Puget Sound, and steep declines in fish and wildlife populations.

Solutions for Our Floodplains

As scientists consider how to address salmon declines and larger storms, they are coming to the conclusion that protecting and restoring floodplains is one of the most important things we can do to help salmon and orca while reducing risk for people.

The first step is to prevent more harmful development in flood-prone areas. In other words, we must stop making the problem worse. The second step is to fix our past mistakes by repairing already damaged floodplains. We can do this by buying out frequently flooded properties, setting back or removing levees to widen the river and floodplain, and restoring floodplains to recreate critical ecological functions.

So, is putting Puget Sound’s next million people in floodplains a good idea? So far, building in floodplains has been bad for people, bad for taxpayers, and bad for fish and wildlife. The question should not be, where are we going to put the next million people. The question should be, where are we going to put them, safely?

Finding a safe home for Puget Sound’s next million people will mean building smarter. Restoring and protecting our floodplains will mean that Puget Sound’s next generation will not just be safer from floods; they will also still be able to see salmon and orca leaping from our waters.

For more information, be sure to read our report: Changing Course: Why Protecting Floodplains is Good for People and Wildlife, and watch our video here.