Local Public Works officials will be on the edge of their seats this season, as the first of the winter storms is set to sweep through the area.

Typically a welcome event for an area wary of drought and particularly after a long dry summer and fall, the winter rains will be a source of concern for the people responsible for flood control and water supply.

At the heart of the matter is the aftermath of the Zaca fire, the largest fire in the history of Santa Barbara County. The blaze, aided by hot and dry Santa Ana winds, took out 240,000 acres mostly in the Los Padres National Forest over four months. It also sent clouds of smoke, ash and dust into the air.

The first of the rains is estimated to hit this weekend and deposit 1 to 3 inches of rain, although county officials acknowledged that winter storms in the area are difficult to predict. Whether or not it rains this weekend, or later in the season, officials are concerned about the state of the county’s watersheds. With no vegetation to absorb and regulate the flow of water, there is an increased risk of flooding.

If that weren’t enough, local water supplies like Lake Cachuma or Gibraltar Reservoir are unprotected from burned debris, uprooted vegetation and anything else that washes down along with the rain.

“Gibraltar’s current capacity is 7,000 acre feet,” said Cathy Taylor, water systems manager for the Santa Barbara city Public Works Department. “Sedimentation can reduce that capacity by half.”

That news is particularly disquieting given that about a third of Santa Barbara’s water supply comes from Gibraltar. Cachuma may be able to hold some of the extra water, but then the issue becomes the bottleneck that would result at the South Coast Conduit, which relays water to Santa Barbara, Goleta and Montecito.

“During peak demand days we would not have the capacity to supply the entire area,” said Taylor.

Additionally, said Taylor, the ash and sediment resin from the fire could result in a sludge that might affect water quality.

Since the fire’s containment in October (fire officials have said there could still be unseen pockets smouldering in remote areas) when both the city and county of Santa Barbara undertook the task of assessing the damage and what actions to take, both jurisdictions have taken several measures to prevent, or at least lessen the impact of the first major rains.

In Cachuma Lake, crews have installed debris booms, a floating barrier system designed to catch and divert logs, branches and other large objects floating by. The county predicts that these racks will also keep the material from endangering boaters and accumulating up against Bradbury Dam.

Meanwhile, city crews have constructed debris booms in the Santa Ynez River, which is predicted to flow much faster now that the watershed has been damaged.

“We’re also looking at recontouring a sand peninsula to slow the flow and have debris fall out there,” said Taylor. Trash racks upstream and other barriers may also do the double duty of keeping debris out of the flow while slowing the water down.

It’s not over yet for Taylor and her crew however. The city has only been able to work within its own property; the surrounding forest is federal property.

“It’s really difficult because the feds do not recognize state emergencies.”

Future projects include a sedimentation mitigation program, and other measures to conserve water capacity while disturbing the recovering watershed environment as little as possible.

For now, Public Works officials are keeping their fingers crossed.

“It will be our first chance to see how the burned-out watershed areas react to significant rainfall and it will give us a chance to measure the success of our work,” said the county’s Deputy Public Works Director Tom Fayram.