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San Luis Rey River mowing reduces flood risk, protects habitat

Published Oct. 30, 2014
This segment of the San Luis Rey River immediately downstream from the Douglas Drive bridge shows the variety of vegetative management necessary to meet the Corps' requirement to reduce the risk of flooding while continuing to provide habitat for protected species.

This segment of the San Luis Rey River immediately downstream from the Douglas Drive bridge shows the variety of vegetative management necessary to meet the Corps' requirement to reduce the risk of flooding while continuing to provide habitat for protected species.

OCEANSIDE, Calif. – The U.S. Army Corps of Engineers concluded seasonal mowing along the lower stretches of the San Luis Rey River here on Oct. 24. The work will increase the flow conveyance in the river for the winter season should the area experience unanticipated rainfall, as well as conserve needed habitat for the federal and state listed endangered least Bell’s vireo.

Part of the vegetative management mowing is conducted under an agreement between the Corps and the City of Oceanside in coordination with the federal and state natural resources agencies for the flood risk management project to minimize flood risk to residences and infrastructure adjacent to the river.

In addition to maintaining the required conveyance in the river, the mowing regime must take into account the presence of protected species and their habitats, which impacts the times of year and particular locations where vegetation management mowing can occur.

“The drought has had a significant effect on viability for plants and for the animals utilizing the river and mitigation ponds for their life cycle requisites of breeding, feeding and cover,” said Tom Keeney, a senior ecologist/biological sciences manager. “So, while we’re cognizant of the need to reduce the risk of flooding, we also have a responsibility to maintain habitat for protected species. The mowing helps us reach both goals.”

Keeney said with the continuation of the drought, the lack of significant storm events, and the lack of precipitation, the vireo’s native vegetation will have to withstand long periods of drought or perish. This is significant because the vireo is directly linked to the vegetation in its habitat for nesting, feeding on insects, and cover.

“If there is no rain or significant storm events, there will be no water for the vegetation in the channel to grow,” Keeney said. “The vegetation will die back leaving only a few areas with there is high ground water table.”

David Van Dorpe, the District’s deputy for programs and project management, said while the work reduces the risk of damage from flooding, the public must still be mindful of the dangers should the area experience heavy rainfall.

“The safety of the public is paramount,” Van Dorpe said. “The San Luis Rey is a dynamic river environment. Right now it’s dry, but with the right amount of rain it could turn into a raging river. With the winter storm season approaching, we need to remember to avoid fast moving water and to stay out of rivers and channels when there is a forecast for rain.