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Op WATFR,p� DEPAUMENT Of <br /> WATER s°9 RESOURCES EVALUATIONLEVEE PROGRAM► ► <br /> a n <br /> o to <br /> OF CA <br /> 0 t 7E i <br /> fblee <br /> eti at r astrf!ap rude 9 a +�er#otxrti fta thoe 5ac�ar nto dad San Joaquin River <br /> # t ttn � of in tfe,arepis,unit dans to laier <br /> s�i�jr���e fi= r + Ie�� 3 ��_ �1F� �e�iBt►n �is provide <br /> To get a detailed picture of the Central Valley flood control <br /> system's current condition,experts study a wide range of criticals . <br /> levee properties,including geomorphology(the forces that alter <br /> land features),levee topography(the configuration of levee <br /> Detail <br /> surfaces),subsurface geologic and groundwater conditions,the _ ,f rea <br /> water levels of rivers and channels,historical events,man- s 5 <br /> made conditions,and erosion conditions.A number of proven <br /> methods and innovative technologies are being used to assess p. b <br /> the levees'structural integrity and identify which areas are <br /> most in need of improvements or repairs. — <br /> Airborne Electromagnetic Surveys £: <br /> Geophysical electromagnetic(EM)surveys are one of the = ± <br /> unique tools experts are using to examine levee subsurface <br /> conditions.Airborne EM surveys are conducted during low- <br /> level <br /> ow level helicopter passes over selected levees.A survey"bird," <br /> which resembles an airborne torpedo(see photo on reverse),is <br /> suspended from the helicopter about 100 feet above the levees. <br /> As the helicopter flies parallel to the levees,the EM technology ; <br /> senses variations in the ground's electrical conductivity to <br /> depths of more than 100 feet underground.The goal is to <br /> map important changes in soil types and ground conditions, :> <br /> identifying zones where permeable soils are present or ', <br /> excessive water penetration is taking place. <br /> These surveys are being conducted in late summer 2007 over <br /> more than 200 miles of levees.From Oroville in the north to :. <br /> Lathrop in the south,the flights are taking place along the <br /> Feather River, Bear River,American River,Sutter Bypass,Yolo <br /> Bypass,Sacramento River,Stanislaus River,San Joaquin River, <br /> — Levees Targeted for Surveying <br /> and their tributaries. <br /> Because homes,businesses,and other sensitive land uses ; eta w xt, <br /> are close to parts of the levee system,DWR is coordinating <br /> with elected officials,community leaders,residents,law <br /> enforcement,and the media to ensure that local communities <br /> are aware of the purpose and timing of the flyovers. <br />