City Watersheds of Sonoma Valley
The City Watersheds of Sonoma Valley program is a cooperative effort among the Sonoma County Water Agency, City of Sonoma, and Sonoma Ecology Center. The program’s elements are designed to improve habitat along city creeks, reduce flooding, manage stormwater, and increase groundwater recharge.
Currently, the program is planning a project to alleviate flooding on First Street West between Depot Park and the Sonoma Plaza. A series of alternatives have been developed, which were presented at a community meeting held on Nov. 19 in Sonoma. The current alternatives include combinations of underground stormwater detention, an underground pipe, and channel improvements.
The November 19 was a follow-up to a meeting held in February, 2015, during which residents and community members expressed concerns about the alternatives that were presented. Following that meeting, Water Agency staff went back to the drawing board to develop new alternatives that took those concerns into account.
NOVEMBER 19, 2015 MEETING MATERIALS
FEBRUARY 4, 2015 MEETING MATERIALS
NEXT STEP: SONOMA CITY COUNCIL MEETING DEC. 7, 2015
Input received at the Nov. 19 meeting will be included in a presentation that will be made to the Sonoma City Council on Monday, Dec. 7, 2015 in the Community Meeting Room (City Council Chambers), 177 1st Street West, Sonoma.
CITY WATERSHEDS FUNDING
The City Watersheds of Sonoma Valley project is a cooperative effort among multiple organizations. The Sonoma County Water Agency and the City of Sonoma are working together on the First Street West project alternatives. Project alternatives may be partially funded by a $1.9-million Department of Water Resources grant for multi-benefit projects that manage stormwater to reduce flood damages.
Water Challenges in Sonoma Valley
Water Challenges in Sonoma Valley
Groundwater Declines: Sonoma Valley meets about 60% of its water supply with groundwater. Groundwater monitoring has revealed groundwater declines in a few areas of the valley that have persisted for decades and appear to be expanding in size. These declines can exacerbate water quality issues by lowering the groundwater table below sea level, allowing for saltwater intrusion from San Pablo Bay.
Flooding: Flooding also causes problems for many residents in many locations in Sonoma Valley. The current Federal Emergency Management Agency (FEMA) floodplain mapping and the City of Sonoma Storm Drain Master Plan show areas of the City of Sonoma that are at high risk of flooding during large storms.
Degradation of Riparian (river-related), Instream and Wetland Habitat: Sonoma Valley is home to many plants and animals that are priorities for conservation. Some fish populations in our area the region are in decline and/or listed as threatened or endangered. Fish barriers, high-velocity water, soil erosion, sedimentation, warm water, and a lack of native vegetation can endanger fish habitat. Additionally, the introduction of invasive, non-native plants have degraded native habitats in a number of ways, including direct competition and crowding with native wildlife and plant species.
Land Use Changes: The historical conversion of natural areas into housing and agricultural development has caused habitat loss and fragmentation and led to excessive sedimentation of streams, de-watering of landscapes, and changes in runoff patterns that have exacerbated flooding.
These challenges are linked
Over time, flood waters have been diverted into stormdrains rather than sinking into the ground to recharge groundwater. Most of Sonoma Valley’s annual rainfall occurs in five or six large storms. Flooding occurs when water can no longer sink into the ground and overflows the stormdrains. The less permeable ground makes it more difficult for stormwater to recharge the aquifer. Historic land use changes have contributed to the overdraft of groundwater and the loss of habitat, excess sedimentation, and changes in the flow of water.
What can we do about it?
Sonoma Valley is implementing a multifaceted approach to building a resilient water supply and healthy ecosystem and community, but there is more to be done. Water conservation programs can be expanded, recycled water can be more widely used to offset potable supply and multi-benefit projects that help reduce flood risks while recharging groundwater can be implemented.
October 2014 Water Workshop Meeting
On October 30th, members of the community attended a public workshop to share ideas and concerns for some of the key water sources or projects in Sonoma Valley. The meeting featured breakout groups, where topics were discussed in small groups with resource and project managers.