Restoring Pools for Creek Critters

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First came the Woolsey Fire, one of the rare wildfires that was as devastating to the creek corridors as it was to everything else. Then came the rains and debris flows that turned the creeks into flat bowling alleys of sediment.

The frogs, newts, snakes and fish that didn’t burn need pools to survive, so this was a double whammy. No trees to provide shade. Pools filled with sediments and only inches deep provide little refuge from predators. Where could the critters go to survive during the hot summer and fall months?

At the annual stream meeting held in February 2019, biologists from National Park Service (NPS), US Geological Survey (USGS), state parks, Pepperdine, and Santa Monica Mountains Conservancy (SMMC) agreed with the Resource Conservation District of the Santa Monica Mountains (RCDSMM) that we needed to do something to try and help.

The idea of digging out the sediments to create temporary pools got everyone excited, and I took the lead to get a grant to make it happen. The Los Angeles Regional Water Quality Control Board was also looking for a way to help and this project fit. With their emergency post-fire funding, the next step was selecting suitable pools and getting the required permits in time to do the work in August. 

NPS also contributed some post-fire monitoring funds to hire a geomorphologist to document the effort so we could assess whether it worked, and how long the excavated pools persist.

Dr. Anne Senter, a geomorphologist with Balance Hydrologics, took the lead. “We are pleased to be partnering with NPS and the RCDSMM in support of creating pool habitat for aquatic species. Geomorphic work in creeks focuses on how physical stream units, such as pools, riffles, and runs, change over time, and how each unit provides specific habitat types to aquatic species. For this project, expansion of deep-water areas in pools will help create important cool summer habitat for frogs, newts, and snakes, as well as low-velocity environments for protection during high winter flows.”

It is always a challenge to obtain permits for work in streams, but especially so when sensitive, threatened or endangered species are involved. California Department of Fish and Wildlife, Regional Board and the Coastal Commission all came through in time and the next hurdle was coordinating with the California Conservation Corps crew in Camarillo to get enough help to do all the work by hand.

Kyle Maxwell, Fish Habitat Assistant, jumped on board to coordinate the field crews.

“We love opportunities like this project to provide hands-on lessons to young adults on how they can restore habitats for native amphibian species such as the federally threatened California red-legged frog,” he said.

Before digging could begin, however, the pools were selected based on accessibility, previous occupancy with sensitive or endangered species, and current condition. They were then surveyed by Senter, assisted by volunteers Liam Hay and Aidan Branney.

“From a physical habitat perspective, repeat surveys of longitudinal profiles and cross sections will help the project understand pre- and post-excavation pool dimensions, and whether those changes hold through the upcoming wet season,” noted Senter. With the preliminary pre-project information in hand, we were ready to start!

At the start of each day, we collected water quality data and moved any critters that happened to be in the work area. Then we set up barriers to prevent them from coming back until we were finished.

RCDSMM Biologist Steve Williams supervised the required temporary sandbag containment barriers to prevent cloudy sediment-filled water from flowing downstream and causing problems.

“It was really fun to find creative ways to divert the clean cascading water and isolate the cloudy water to prevent downstream impacts,” Williams said.

Thanks to a handy submersible bilge pump powered by a most unusual battery system designed by local Topanga engineer Scott King, it was possible to keep the water levels inside the barriers as the excavation progressed.

Doing the excavation work was pretty laborious and we were grateful for the strong shoveling and bucket brigade team to assist.

The California Conservation Corps members do all kinds of amazing service projects, although their main focus is fighting wildfires. They are used to hard work in challenging situations, just the right folks for this project! The six-to-nine crewmembers literally dug right in and were able to excavate a pool a day for six days.

“The C’s are like a well-oiled machine once they figure out the plan,” noted Williams.

For several days we also had the expertise of Vet Corps Fisheries members Elijah Mitrano and Zach Hoagland. They supervised the placement of the sediment above the floodplain, taking care not to bury any native plants (except for some poison oak!).

Dr. Katy Delaney, wildlife ecologist for the National Park Service has been in charge of the reintroduction of endangered California red-legged frogs throughout the SMMNRA.

Delany noted, “We’ve never tried a project like this and we’re grateful for the excellent work of the CCCs. Restoring a bit of depth in the pools should provide good habitat for native amphibians throughout the winter.”

Post-excavation surveys will occur in September and already we have seen the critters returning to their enhanced pool homes. We are all looking forward to coming back in the winter to see how the pools and their inhabitants fare.


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