The title of my favorite Led Zeppelin song (yes, I'm old) leads in to a discussion of something we never think much about - until they break: the flood-protection levees lining the lower stretches of the San Lorenzo River and Pajaro River.
This past January we saw the Pajaro levee fail on the Monterey County side, flooding the town named for the river - Pajaro. Investigation of the causes pointed to, among other things, a failure to maintain the levee.
Santa Cruz took notice of that failure, and is also facing the need to re-certify the ability of the San Lorenzo levees to protect nearby residents from similar failures. That need led to the odd sight users of the Riverwalk have noticed: numerous small puddles of concrete grout scattered along the levee top.
The photo above-right is from a good article published recently by Lookout Santa Cruz. It explains that the purpose of the grouting is to fill ground squirrel burrows that reduce the structural integrity and water-retaining ability of the levees, which are really nothing more than two long piles of rocks. The article goes on to look at contractor errors in distinguishing rodent burrows from native-plant restoration diggings, but that's another story.
Local history buffs will know that the levees (along with the concrete Branciforte Creek channel) were designed by the U.S. Army Corps of Engineers (ACE) in response to the major flooding of December 1955. Part of the deal was that ACE would maintain the levees at first, gradually handing over responsibilities to the city/county. As the Lookout article explains:
The city took over management of the levee from the U.S. Army Corps of Engineers in July 2020 following the completion of the levee construction, which began in 1955. The management changeover started a three-year clock, which runs out this month, for the city to get accreditation for the levee from the Federal Emergency Management Agency (FEMA). If received, this would allow residents living near the river to maintain their discounted flood insurance.
Another thing highlighted in the Lookout article is how the local nonprofit Coastal Watershed Council has been very active in all matters relating to the health of the San Lorenzo River. Two thumbs up to Executive Director Laurie Egan, CWC staff, and the many volunteers who assist in these efforts.
