New study: Conservation land could stave off flooding
Chico Enterprise Record - 4/13/03
By Heather Hacking, staff writer

The Nature Conservancy, a major player in buying land for wildlife along the Sacramento River, is trying to prove its purchases benefit both wildlife and farmers.

By buying habitat and flood-prone agricultural land along the river, then carefully choosing what to plant on the land, the Nature Conservancy believes it can protect good farm land from harm.

It is hoped that a new computer modeling program can also be applied to solving problems such as the failing J Levee at Hamilton City, or even the growing gravel bar at the M'&'T Ranch.

The study tracks the depth and speed of flood waters on different types of land. Water moves differently on sand bars than it does on thick riparian jungle. The water flows differ on riverside meadows than they do on savannah-type plantings that include shrubbery.

The water modeling report is the second of four planned by the Nature Conservancy, and was funded as part of a CalFed grant to create a management plan for four properties the Nature Conservancy owns along the river.

Conservancy leaders are excited that preliminary reports indicate that careful selection of types of habitat could lessen the effects of flooding near Highway 32, like that in 1995.

Wise planning could "both restore the ecosystem and reduce damage of high water by concentrating high water on conservation land," said Sam Lawson, director for the Nature Conservancy's Sacramento River project.

The group recently bought what was known as the Sunset Ranch adjacent to the Sacramento River, just south of Highway 32 east of the river. The group also owns a chunk of land east of that property.

The Sunset Ranch once was a walnut orchard, but those trees have been pulled out. Now the group is looking at what to plant, and what would best fit with plans to allow the river to more naturally meander. That's a choice the study will help the group make.

The study analyzed water flows from river mile 194, at the M'&'T Ranch, to river mile 202, just above the Glenn-Colusa Irrigation District intake.

First consultant Ayres Associates compiled topography data to create a computer model to predict flows under different scenarios.

Ayres based the study on high-water levels during the 1995 flood. The different land uses were analyzed for what is called "roughness."

Roughness depends on the type of land use such as dense riparian habitat, orchards, pasture land or sand bars. Heavy plantings such as orchards and riparian forests hold the water for a longer period of time, while pasture land and sand bars are less rough and the water moves across them swiftly.

The researchers then spent time with landowners in Butte and Glenn counties to have them look over the model. They wanted to make sure the data coincided with their experiences in the 1995 flood. In some cases, the model had to be refined to take into consideration things like sandbagging done during the height of the '95 flood.

Then the researchers ran the model back to 1995 to make sure it "predicted" what actually occurred when the high water came.

Satisfied with the accuracy of the program, the researchers then were able to plug in changes of land use to see how agriculture-to-habitat projects would affect areas downstream.

That information told the conservancy that the land recently purchased south of Highway 32 should be left like a meadow, with native plants. That habitat can speed up the water during floods and lessen the depth of water that floods Highway 32. The water might be up to half a foot lower, the report indicates.

This change in habitat could also increase water depths on U.S. Fish and Wildlife property on the west side of the river downstream and slightly decrease the water depths on property around Scotty's Boat Landing on the east side of the river.

In other words, less water on the highway and private land; more water on public lands, just where the resource agencies want it.

"The restoration is intended to restore close to what nature would have put there naturally," Lawson said.

At a recent meeting of the Sacramento River Conservation Area Forum, Lawson said the modeling might also be useful for other studies along the river.

For example, the river tends to deposit gravel near M'&'T Ranch and the city's sewer treatment plant south of the washout. Last year a gravel bar was dredged, but M'&'T and the city are looking for a long-term solution.

Lawson said the model could be applied to try to find out what the best long-term solution would be.

He said the benefits will also affect the east side of the river when floods occur.

By creating habitat in areas where the river frequently floods, "Butte County won't have to go out and sandbag to protect marginal agriculture," he said.

The Nature Conservancy is also working to use some of its land purchases to help Glenn County deal with the problem of financing a new levee to protect Hamilton City from flooding. Glenn County supervisors have said the group has been a key player in solving that problem, yet the county leaders are still skeptical in general of the Nature Conservancy buying land along the river.

Questions have been raised about the cumulative impact of land that is being purchased and restored to habitat. The conservancy owns about 800 acres along that stretch, and is working on deals to buy three more properties.

Soon, all but a few sections of land will be owned by the group or other public agencies including the Department of Water Resources, state parks, the U.S. Fish and Wildlife Service or the state Department of Fish and Game.

The Nature Conservancy tends to buy land, convert it to habitat and then turn the land over to government agencies. Over the years, about 18,000 acres within the Sacramento inner river zone from Keswick to Verona have been protected with the help of the group. More than half of that land was already in habitat, Lawson said.

The long-term plan is to allow the river to meander more naturally.

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