PENDLETON — Floods, like all natural disasters, can cause costly devastation to property as well as the landscape, yet when waterways are properly functioning damage from high flows can be abated.

Rivers and streams that are not impinged by development like roads, railways or levees periodically spill over their banks, recharging groundwater within the floodplain. The direction of the Confederated Tribes of the Umatilla Indian Reservation’s fish habitat program is to design restoration projects that allow waterways to absorb flood impacts while protecting property and infrastructure.

Last year, a 500-year flood inundated communities along the Umatilla River, washing out roads and bridges and destroying homes. Mike Lambert, fish habitat program supervisor for the Tribes, said he didn’t believe there was any significant damage to salmon and steelhead runs, but there is always a potential that high water can flush juvenile fish downstream from their rearing habitat.

“Those fish get displaced downriver into confluences and tributaries where the water is warmer,” he said.

Juvenile fish need clean, cold water to thrive, hiding cover from predators and slack water where they can rest, feed and grow — typically in the upper reaches of rivers and streams. When the juvenile fish are pushed downstream, Lambert said, many will die and the population’s overall rate of survival is reduced, decreasing the number of returning adults available for harvest and reproduction.

Listed as threatened on the Endangered Species List, Chinook salmon and steelhead runs have been decimated in recent years largely because of warm ocean conditions, setting off a cascade of negative effects starting with a decline in salmon and steelhead’s natural prey species.

While not much can be done about ocean effects, protecting the habitat where adult fish spawn and die and juveniles rear in the colder, more pristine reaches of rivers and streams is an important focus area for the Tribes.

On the reservation, Lambert said tribal staff have taken a hard look at the levees protecting their land and homes, and their response to past flooding.

“We did a levee assessment to evaluate the importance of each of those levees, balancing protection of infrastructure with the opportunity to restore floodplains to a more natural condition,” he said.

Levees deemed not worth maintaining were removed, Lambert said, giving the Umatilla River more space to spill its banks into the floodplain, while some were left to further protect land from being eroded away.

Lambert said as the climate continues to warm over the next 30 to 40 years, he expects wetter, flashier systems.

“It’s important to look at ways to allow the river to function more naturally when floods do occur, while protecting people, infrastructure and agricultural land,” he said.

In addition to removing structures like levees to allow the river to flow and change course, Lambert said the Tribes are considering purchasing land from willing landowners with Federal Emergency Management Agency hazard response funds in order to convert those floodplains back to a more natural state.

Floodplains can be prime rearing habitat for juveniles, so restoring them is part of a long-term investment in securing what the tribes consider “first foods” — historic food sources like salmon and steelhead that sustained indigenous people for thousands of years.

Lambert calls it a “holistic approach.”

“The Tribes are working with people in the community, how flooding impacts their homes, while looking at the long-term health of the river and floodplain, and where we are going to be in seven generations,” he said.

CTUIR’s Natural Resources Director Eric Quaempts said restoring and protecting habitat for first foods guides the Tribe’s management of all resources.

“The CTUIR has a river vision to guide our restoration efforts to improve water quality and fish productivity so that our tribal members can enjoy quality water and treaty harvest of First Foods that include salmon and other fish,” Quaempts said. “Fish and other First Foods are critical to Tribal religion, culture, and healthy diets. The river vision emphasizes the importance of floodplain processes, including high flow events, to produce these First Foods.”

Healthy floodplains benefit everyone, Lambert said. When the energy of a river can be dissipated over a greater area, as opposed to being confined, groundwater is recharged, benefitting municipal drinking water and agriculture. And from the Tribe’s perspective, he said, water is the first of the first foods.

“Cleaner, cooler water supports life in general,” he said.

As for the overall functioning of rivers and streams, Lambert said flood waters transport nutrient rich sediment across the floodplain, improving crop production and tree growth along the river’s banks and increasing biomass throughout the system.

While the Tribes have taken a hard look at the areas where flood waters threaten homes and property on the reservation, Lambert said much of the floodplain restoration occurred in headwaters of tributaries to the Umatilla, where adult salmon spawn and juveniles rear.

Up the hill to the east of the reservation, the Tribes restored nearly 9 miles of Meacham Creek, removing levees and allowing the creek to spread out when high waters flow. Lambert said there was a vast difference in damage to the railroad in 2020 compared to another historic, devastating flood.

“In the 1964 flood, 20 or 30 locations of the railroad were disconnected and it was almost a year to get it back and running through Meacham Creek,” Lambert said. “Last year, the railroad was back up and running in four days.”

Restoration on rivers, such as the upper Grande Ronde, upper Walla Walla and south fork of the Walla Walla, also held up well to flood waters. Lambert said upstream and downstream of the project areas showed signs of damage after the 2020 floods, while a house within one of the restoration sites wasn’t harmed.

As for river systems and the future of healthy fisheries, Lambert said floods sort and transport wood and cleaner sediment downstream, providing what he called “decadal benefits.”

“A healthy, resilient, dynamic floodplain is healthy for fish and people, and both are important — one sustains the other,” he said.