Control floods with geotextile cofferdams:

Portable water barriers provide an alternative method of preventing costly property damage.

   Condo owners approve dams.
   A group of Sacramento, Calif., residents are glad that they learned about AquaDams®, albeit too late the first time. The Woodside Condominiums are situated on a pair of sloughs in northeastern Sacramento. Because of this location, the condos are often in danger of being flooded during winter months. In February 1997, 85 of the community’s homeowners incurred a total of $1 million in property damages and $1.5 million in personal property losses during northern California floods.

    In 1998, homeowners had anticipated the storms and were prepared, according to Judy Munz, Property Manager. In December 1997, crews installed 1,700 feet of one to three ft high AquaDams® around the complex. Because each dam comes with a connecting collar, linking the differently sized units together was a simple process. Had it been necessary, the barriers could have been cut to fit onsite specifications.

    According to Munz, the structures were erected in a matter of hours. Sandbagging would have required at least 30,000 sand­bags and considerably more time to protect the 56 acre parcel. Although this installation proved to be a preventive measure, maintaining the homeowners’ peace of mind was an additional benefit.

   Two 100 year floods.
    The Army Corps of Engineers has effectively used geotextile dams numerous times. During heavy storms in February 1997, the Sutter Bypass, located an hour north of Sacramento, California, threatened to overflow its levee banks twice in the same month. Between $5 and $10 million had been spent to rebuild the failed levee following a 100 year flood, and high water from a second 100 year flood the following month threatened to wash away the newly constructed levee.

    The corps had just seven hours to install three foot high dams along 800 feet of the levee to beat the level predicted for the rising flood waters and save the new levee. Ordinarily, this would have been impossible, requiring some 25,000 sandbags to compete, but using AquaDams®, the job was completed in time to avert disaster. The rebuilt section of levee held, the flooding river receded in three days, and California Conservation Corps crews dismantled and removed the dams in three hours.

   Clear Lake cofferdams.
    The Skylark Shores Motel Resort is situated near the edge of Clear Lake in northern California’s Lake County. Typically, the lake is considered full when water reaches the height of 7.6 feet within the levees that surround the lake, with floodwaters at nine feet. During California’s 1998 El Nino, Clear Lake’s levee water level was 11.7 feet, its highest point since 1909. It was a panic situation for the Skylark’s manager, Chuck Roof. Without some form of damming, Roof was certain that during the storm season, the Skylark’s lakefront rooms would have been standing in water two feet deep. Worse, the flooding would have necessitated closure of the facility, and it could also have resulted in dangerous electrical problems. To secure the lakeside portion of the property, a three ft water barrier was installed on the property’s lawn between the lake and the motel. A four ft unit, erected in front of the resort’s lower rooms, acted as a wave barrier and coffer dam. In total, close to 1,000 feet of geotextile dams filled with the lake’s own potentially destructive waters were positioned around the resort.

   The three and four ft high dams, composed of 100ft and 240ft barrier sections held end-to-end with collars, kept the entire resort water-free and operational. The Skylark was the only dry property in the vicinity. Its accessibility made it possible for the Red Cross and the National Guard to use the resort as a headquarters during their flood relief efforts. Minimal grass damage beneath the footprint of the dams was the single downside to the flood protection effort, according to Roof. With reseeding, the grass recovered in less than three months.

    Augment Levee System.
     Clear Lake Lands Coordinator Skip Simkins oversees several miles of Lake County’s Clear Lake levee system under the auspices of the public trust for the state of California. Simkins said that maintaining even several miles of the lake levees can be disheartening during floods.

     When extreme flooding occurs, Simkins has had as many as 100 people working on different levees at the same time. “Manpower is a really important thing in flood situations,” he remarked. Prior to 1995, sandbags were the primary line of defense for rising floodwaters along this section of reclaimed levee-protected land. Then Simkins learned about a water-filled geomembrane alternative.