A Place for Floods to Go

The moment of truth for the development of Ada County since 1955 has arrived.

For more than 27 days, the flood-swollen Boise River has rolled through Boise, Garden City and Eagle at 8,000 cubic feet per second with only minimal damage and inconvenience. Today it flows at 8,600 cfs as measured at Glenwood Bridge and federal dam managers say they may have to raise the flows again.

We have come to this point because those before us made a series of decisions that allowed Boise to become a thriving urban center with the Boise River at its heart. Lucky Peak was built primarily for flood control and when it was completed in 1955 it gave the U.S. Army Corps of Engineers the chance to regulate spring runoff.

This provided Boise the opportunity to build in the flood plain, but such development remained a risky investment for developers. By the 1960s, Boise residents were beginning to see their river in a different light — no longer simply a channel for irrigation waters and a sewer to carry away human and animal wastes and the effluent from processing plants on its banks.

The decision to stop dumping sewage directly in the river in the 1950s allowed the river water quality to improve, enough that people were regularly floating in rafts and inner tubes during the summers in the 1960s. The City Council passed a resolution in 1966 making a greenbelt park along the river a city goal. Little did they know their dream for a recreational trail would be nearly as critical for flood control as levees and even dams.

Development of the 25-mile Boise Greenbelt required the city to condemn some property and to even force a hotel to remove a swimming pool built across the eventual path. But public support let it become the popular transportation and recreational corridor it is today.

Passage of the National Flood Insurance Program in the late 1960s, and its embrace by Boise in the 1970s, created a system that allowed development in Boise’s flood plain while managing the financial risk.

In her wonderful 1993 book “When the River Rises,” former city planner Susan Stacy tells how city leaders both leveraged demand for the Greenbelt and traded away flood plain that, were it undeveloped today, would offer even more landscape in which the river can spread out.

As the river rises this spring, the compromises made in Boise and downriver in Garden Valley and Eagle will become obvious. Without such compromises, of course, the Valley would not have the thriving communities it has today.

Through these development tradeoffs, Boise and Treasure Valley residents have always placed value on the ecological attributes here: Bald eagles, trout, wood ducks and the cottonwoods, whose very survival is tied to regular flooding. And that’s why today the river has taken back every place we give it along the Greenbelt, naturally spreading life with its flood flows.

When I first covered the 1997 flood season, there remained a chasm between those who saws floods as beneficial and those who sought to control the river by forcing it into a constrained, engineered channel behind levees and dikes. Flood Control District 10 saw cottonwoods as potential obstructions that needed to be cut back, severely at times.

Environmentalists bemoaned the cutting of any trees and sought to remove the levees to let the river make its own path in its historic flood plain. Today the two sides have developed a collaborative relationship through the Boise River Enhancement Network.

“We are all much more open to collaboration and partnership,” said Liz Paul, one of the valley’s most persistent and effective river voices.

The flooding of the Greenbelt is a success story, she says. It keeps waters out of people’s homes and lessens downstream flooding, despite what she considers over-development in the flood plain. She notes that Boise City Parks like Esther Simplot Park and Marianne Williams Park are specifically designed to take the flows that are spreading across their expanses and into their ponds.

“One of the healthiest flood plain areas is right at the Veterans Memorial Park Bridge, upstream and on the south side of the river, that’s absorbing the flow right now,” Paul said.

As Boise River flows rise, you can expect Warm Springs Golf Course will absorb some of those flood flows, as will Ann Morrison Park. When that happens, remember there has never been any doubt among river managers or community leaders that this day would come — and, one day, even worse flooding.

Preservation of the Greenbelt and the riverside parks has reduced the impact. Only by recognizing and accepting our limitations can we reduce future losses.

“The No. 1 thing to do is not allow further channelization of the river and not allow the river to be cut off from the flood plain and the side channels,” Paul said.