Wasatch County officials are bracing for runoff of 2,500 percent above normal from Wasatch Mountain this spring as a result of a major fire that swept the area in August.
Eckhoff Watson & Preator, consultants to the county, estimate that during a major storm, water would run off the mountain at 338 cubic feet per second. The Soil Conservation Society puts the estimated rate at 220 cfs, compared with 12.7 cfs before the fire. Even at 12.7 cfs, sandbagging has been necessary.The society has indicated it will fund about $170,000 of a rehabilitation project, but consultants have estimated the total cost, including flood control, at more than $435,000.
In any case, a major flood could be expected to cause extensive damage.
Floodwaters would rush through the Midway Cemetery, two power substations, several homes, and would seriously damage farmland.
County commissioners, who met last week to begin discussing how to protect property, plan to begin flood-control work immediately.
An embankment, 600 to 700 feet long and four to six feet deep, will be built to divert runoff as it leaves the canyon. From there, some of the water will be spread out in open fields and the rest will be channeled until it reaches Epperson Ditch and overflows into Snake Creek.
Public works director Kent Berg said he is stockpiling materials for sandbags to be used as a last defense against flooding.
If a major storm occurs during the next several years, before seeds and shrubbery replanted on the mountain mature enough to hold back runoff, Snake Creek will not be able to hold the water.
Commissioners said it would be impossible to control even 200 cfs, but hope to keep damage to a minimum.
Although state officials have verbally agreed to provide state funds for most of the costs, the commissioners plan to meet with them and get specific written commitments.
In particular, they hope to get a commitment for funds from the Utah Division of Parks and Recreation because the fire burned mostly state park land.
The SCS funding is primarily concerned with watershed and deer-range rehabilitation rather than potential flooding, and the society is not expected to participate in extensive flood-control measures.
Commissioners noted that if state and federal agencies don't provide money to help prepare for flooding, they will be responsible for damages afterward.
They're also concerned about the county's liability for damages that could result from flood-control construction. All but one of the property owners have agreed to allow dams, channels and whatever else is needed to control flooding on their lands.
More research and study is needed to determine where to build flood-control structures, but construction on the embankment and ditch work will begin immediately.
Meantime, more than 35,000 pounds of grass, sagebrush, bitterbrush and alfalfa seed is being dropped by helicopter onto nearly 2,900 acres. Some 900 pounds of seed has been sowed on 215 acres.