Almost 5 years of drought, now combined with recent rainfall-induced flooding, has weakened California’s levees. Culprits are soil cracking that allows water seepage, soil-strength reduction, land subsidence and erosion, all of which NWNL observed on its California Spotlight expeditions in 2014 and 2015. Fifty-five percent of California’s levee systems are now in danger of failing in the event of a flood or an earthquake. If the levees fail, water quality could be compromised for over 23 million people.
Levees are sand and clay earthen embankments which regulate water levels and protect dry land from floods. More research, risk science, community education and stakeholder collaboration are crucial to improving levee resilience.
Related article in Science Magazine: https://grgusyd.files.wordpress.com/2015/08/vahedifard-et-al-2015_ca-drought-levees_science.pdf