The South Branch Arroyo Conejo (SBAC) is a large storm drain channel system located in Newbury Park. Approximately 300 properties adjacent to the SBAC Channel in Newbury Park have faced the need to carry flood insurance since the Federal Emergency Management Agency (FEMA) revised National Flood Insurance Program (NFIP) maps in 2010. 

In 2011, the City sought assistance from the U.S. Army Corps of Engineers (USACE), which indicated that federal funding could be available for flood channel improvements, benefiting local residents and potentially allowing them to avoid costly flood insurance. By 2014, the USACE had designated the SBAC for further investigation and began a Phase II Feasibility Study in 2015 to evaluate potential mitigation improvements. 

In 2020, the USACE ultimately recommended against a full Feasibility Study, citing lower cost-benefit ratios than initially expected. The agency noted that flooding was likely due to insufficient capacity in the local system rather than issues within the floodplain channel, which limited potential federal support. Consequently, the City and the County’s Watershed Protection District (VCWPD) were advised to seek local funding options for flood mitigation.

In response, the City and VCWP selected an engineering consultant to perform a local hydrology deficiency study. The purpose of this study is to identify current drainage/flooding conditions in the study area, and potentially submit an updated map to FEMA reflecting existing hydrology conditions that may result in the removal of some properties from the flood zone. If approved by FEMA, these properties would no longer be required to purchase flood insurance.

In 2023, the City and VCWPD signed a Memorandum of Agreement (MOA) and a cost-sharing arrangement based on the overall level of effort for each jurisdiction. City Council approved the MOA on July 18, 2023, and the County Board approved it on July 25, 2023.

Given the significance of this study, the City desires to gather information and data from any interested person/party regarding the study area, including flooding and drainage history on any property(ies), drainage or hydrology studies and reports done on any property(ies) in the study area, and any information or data that will assist in the preparation of the study.

All information received will be evaluated by the City and County staff and consultants. and feedback from the community may prompt the City to conduct additional hydrology analyses, evaluate alternative mitigation projects, and or develop other recommendations/findings for consideration. Therefore, the community's participation and input on the project and watershed, including receipt of concerns or areas of requested focus, are critical to the project's map revision goal. 

To provide feedback or request additional analysis, please click here.

Project Timeframe

Community information and data collection in Spring and Summer 2026.

The final draft of the hydrologist's study is anticipated to be completed by early 2027.

Budget/Funding

Approximately $500,000 from MI 2527, General Fund–South Branch Arroyo Conejo Floodplain Improvements Study, with up to 40% contribution by the County. 

Project Impacts

The project goal is to relieve the economic pressures of flood insurance premiums on qualified property owners and to allow greater flexibility in the redevelopment and improvement of buildings currently located within the federally defined floodplain. Mitigation of the floodplain risk would also reduce flood impacts on local schools, the Newbury Park library, arterial roadways, and local businesses. 

Project Highlights and Benefits

The focus of the hydrology study is to model the existing local drainage system to more accurately reflect actual conditions and identify potential capital improvement projects to mitigate local flooding. The project goal is to reduce or eliminate 100-year flooding, i.e., flooding that has a 1-percent chance of occurring in any given year, thereby reducing flood risk and flood insurance costs to neighborhood properties.