Department of Water Resources
A daily compilation for DWR personnel of significant news articles and comment
March 21, 2007
1. Top Item
New analysis of old levees; Helicopters with lasers will speed the state's profiling process
By Alex Breitler, staff writer
Chinese laborers toting shovels and wheelbarrows built many of the levees around
Now gadgetry of the 21st century will help us learn how they are holding up.
Next week, helicopters are expected to fly over urban levees from Lathrop to Marysville, using lasers to map the elevation of each berm within a few inches.
The laser beams bounce off the ground and return to the helicopter; the amount of time that takes tells experts the exact height of the levee.
The result is a topographical profile of each levee and maybe a clue to whether it is apt to erode or allow water to seep through.
"We're hoping to do 350 miles within two weeks, versus people going into the field and doing a survey by hand," said levee expert Claudio Avila of the Department of Water Resources. "That's the big advantage."
The work is part of a $35million project evaluating urban levees - those that provide protection to communities of 10,000 people or more.
Crews already have drilled into many of these levees and removed soil samples to learn more about the composition of the barriers. The laser project is an extension of this work,
The state says it will try to strengthen susceptible levees after the evaluations are finished later this year.
During storms and spring runoff, rivers and streams push against levees and create a natural imbalance with the underground water table on the dry side. This causes water to seep through or beneath the levee.
The lasers to be used in the evaluations take 10,000 measurements per second, providing data that can be pored over to form a profile of each levee. #
http://www.recordnet.com/apps/pbcs.dll/article?AID=/20070321/A_NEWS/703210325
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