Heavy rainfall tests Steigerwald’s newly reconnected floodplain

A little more than one month after its completion, the new floodplain at Steigerwald Lake National Wildlife Refuge has met its first challenge.

Local and regional officials welcomed the public back to Steigerwald on May 7 after a nearly 2-year closure for a project that reconnected the Gibbons Creek watershed and Steigerwald Lake to the Columbia River in an effort to prevent flooding in the area, including at the Port of Camas-Washougal’s industrial business park.

On June 13, after days of heavy rainfall, melting snowpack and an unusually wet spring, the river crested its banks near the wildlife refuge, testing the new floodplain.

Chris Collins, the program lead for the Lower Columbia Estuary Partnership, the Portland-based nonprofit that coordinated the reconnection project, said he wasn’t shocked by the timing of the flooding.

“(We’ve noticed) how often we have big flood events right after we finish projects,” Collins said. “We joke that the best predictor of an upcoming flood is us completing a construction or restoration project. But we designed the project with events like this in mind. We are excited to have the water back on the site. It is a good test.”

So far, the refuge’s newly constructed floodplain is passing the test.

“The reconfigured system is new, everybody is excited to be back out there, we open it up and a month later we get a big flood like this. It’s a great opportunity to talk to the users and the community about what this means and provide some context,” Collins said.

The project was meant to “bring floodwaters back to where we want them so they can promote wetland habitats, support fish and wildlife, and better protect areas where we don’t want floodwaters, like the Port of Camas-Washougal and the city (of Washougal),” Collins said. “This is not a flood level that’s going to fundamentally test the levee system, but the trails thus far seem to be holding up just fine. The trails were designed to be occasionally inundated, so we don’t anticipate any problems there.”

The Columbia River water level surged from its normal 12 feet to about 16 feet last week, according to the National Weather Service office, which issued a flood warning for parks and trails in Clark and Multnomah counties on June 13.

Collins said the river is experiencing a five-year flood event, which has a 20% chance to occur in any given year.

“We’ve had a very wet spring,” he said. “And we actually ended up having a pretty good snowpack in the basin, and it’s melting off late. A variety of things are converging to give us some high water levels. The river is high now, for sure, but this is not at all unprecedented. The river has reached this elevation about five times in the last 15 years. It lasts for varying amounts of time. It can last for a day. Several years ago, we saw these water levels persist for about a month. They can last for a long time, or they can just come and go and be very fleeting.”

Collins said flooding at the refuge isn’t a bad thing — in fact, it may prove to be beneficial,

“Flooding is great on floodplains like Steigerwald, where we want to have flooding,” Collins said.

The refuge reconstruction project also created two new setback levees to protect public and private lands from the natural ebb and flow of the floodplain. The rising water levels suppress invasive plant species and favor native wetlands plants, such as wapato.

“When the habitats out there, particularly the wetlands, are flooded, it’s beneficial to native wetland plants and detrimental to invasive species,” Collins said. “Hundreds of acres of wetlands at the site, many of which we didn’t touch during construction, will benefit from these floods, just by moving the needle away from invasive species and towards native wetlands plants like wapato.”

Collins also said that flooding provides habitats for waterfowl, heron and other birds, as well as juvenile salmon.