One Across, One Down: A Help Up?
The broken wooden fish ladder behind Ross post office, long obstructing migrating fish, may be removed, after many studies of flow dynamics, property issues and environmental concerns. This is the interface that launched a thousand sheets. Photo by Matt Smeltzer
Improvements to the Concrete Channel
The State Coastal Conservancy has provided funding for two projects related to modifications of the concrete channel: one project will develop 65% designs to remove part of the concrete channel at its downstream end and the second will prepare 35% designs to modify the concrete channel to improve fish passage upstream of the Math-Science-Nursing Bridge on the College of Marin Campus.
The Coastal Conservancy is a California state agency, established in 1976, to protect and improve natural lands and waterways, to help people get to and enjoy the outdoors, and to sustain local economies along California’s coast. It acts with others to protect and restore, and increase public access to, California’s coast, ocean, coastal watersheds, and the San Francisco Bay Area. Its vision is of a beautiful, restored, and accessible coast for current and future generations of Californians. More about the Coastal Conservancy’s program can be found at the Conservancy’s website at scc.ca.gov. Information about the Marin Community Foundation can be found at marincf.org.
Project to Remove Lower Reaches of the Corte Madera Creek Concrete Channel
The project illustrated below would create approximately 0.6 acres of new tidal and wetland habitats and 0.8 acres of new riparian and upland transitional habitats by removing or lowering approximately 625 lineal feet of concrete flood channel wall. Importantly, the new habitats would use appropriate native vegetation and be designed at elevations that would accommodate sea-level rise so they would be resilient to climate change. The 65% designs will be prepared in Fall 2020 and used to seek construction funding.
Other notable project elements include:
- Hydraulic analysis to confirm project would not increase flood water surface elevations
- Improvements to an existing multi-use pathway and “pocket-park” adjacent to the creek
- New vegetated basins and bio-swales for stormwater run-off to replace existing storm drains that feed directly into the creek, and
- Re-use or recycling of all materials removed for the creation of the new habitats.
Improvements to Fish Passage in the Corte Madera Creek Concrete Channel
Michael Love & Associates (MLA) evaluated the use of new, larger resting pools to improve passage success within the concrete channel in 2007. The analysis identified two configurations of pools that would provide low velocity zones suitable for steelhead to rest at all fish passage flows and that would minimize sedimentation. One was better for straight reaches of the channel and the second better in curved reaches. Current efforts are responding to an additional complication: more water needs to be accommodated in the concrete channel to reduce flooding. MLA and engineers from GHD, consultants working with the Flood Control District on the project, are designing measures to meet all three objectives. The 35% designs are expected in mid-2021.
They Must be Bats!
In mid-April, just after noon, two bat rays (Mylobatis californica) were spotted in the McAllister Avenue slough, a remnant of Corte Madera Creek’s original alignment, just downstream of the concrete channel in Kentfield. Every spring these rays gather in the shallow warm waters of coastal California’s bays and sloughs to feed, mate, and give birth. The creature’s wingspan can exceed five feet. Photo by Nick Salcedo