REPORT/RECOMMENDATION TO THE BOARD OF SUPERVISORS
OF SAN BERNARDINO COUNTY FLOOD CONTROL DISTRICT
AND RECORD OF ACTION
March 24, 2026
FROM
NOEL CASTILLO, Chief Flood Control Engineer, Flood Control District
SUBJECT
Title
San Bernardino County Flood Control District Hydrology Manual Updates
End
RECOMMENDATION(S)
Recommendation
Acting as the governing body of the San Bernardino County Flood Control District:
1. Find that approval of the updated San Bernardino County Flood Control District Hydrology Manual is exempt under the California Environmental Quality Act Guidelines, Title 14 of the California Code of Regulations Sections 15061(b)(3) (Common Sense Exemption), 15378(b)(2) (General Policy), and 15378(b)(5) (Administrative Activities).
2. Approve the updated San Bernardino County Flood Control District Hydrology Manual to provide modern, accurate, and transparent hydrology tools for residents, public agencies, engineers, and developers working within the County.
3. Authorize the Director of the Department of Public Works or Chief Flood Control Engineer to approve future revisions to the Hydrology Manual on an as-needed basis.
4. Direct the San Bernardino County Flood Control District to file the Notice of Exemption in accordance with the California Environmental Quality Act.
(Presenter: Noel Castillo, Chief Flood Control Engineer, 387-7906)
Body
COUNTY AND CHIEF EXECUTIVE OFFICER GOALS & OBJECTIVES
Promote and Fulfill the Countywide Vision.
Improve County Government Operations.
Operate in a Fiscally Responsible and Business-Like Manner.
Provide for the Safety, Health and Social Service Needs of County Residents.
FINANCIAL IMPACT
Approval of this item will not result in the use of Discretionary General Funding (Net County Cost). The San Bernardino County Flood Control District (District) is funded by property taxes, fee revenue, and other local, state, and federal funding.
BACKGROUND INFORMATION
The San Bernardino County Flood Control District (District) is responsible for the operation and maintenance of more than 3,000 flood control facilities, including channels, basins, storm drains, dams, and levees throughout the County. To support consistent and reliable hydrologic analysis within its jurisdiction, the District relies on its Hydrology Manual, which serves as the standard reference for all hydrology studies prepared for San Bernardino County (County) review and approval.
The District’s current Hydrology Manual was last comprehensively updated in 1986, with a limited addendum issued in 2010. While the Hydrology Manual has continued to be used successfully, many of the underlying base data sources have remained unchanged for decades. During this time, significant technical, regulatory, and administrative advancements have occurred in the field of stormwater management, necessitating updates to improve accuracy, consistency, and transparency.
The Board of Supervisors (Board) has previously taken actions related to the update of the District’s Hydrology Manual. On January 10, 2023, (Item No. 57), the Board approved a contract with WEST Consultants, Inc., to provide professional engineering services to update the Hydrology Manual.
Subsequently, on November 5, 2025 (Item No. 53), the Board approved a one-year extension of the Contract with WEST Consultants, Inc., to allow for the completion of the remaining work and continued support of the update effort.
The proposed update to the Hydrology Manual is intended to modernize supporting data and tools while maintaining the core hydrology equations and existing design methodologies currently in use. This effort does not represent a shift toward more conservative design criteria; rather, it is a data innovation initiative focused on improving reliability, consistency, and ease of application for users.
As part of this update, the District will provide the following resources at no cost to residents, public agencies, engineers, and developers:
• Acceptance and use of the most recent National Oceanic and Atmospheric Administration (NOAA) precipitation data as the standard precipitation source
• Hydrology spreadsheets supporting the Rational Method and Unit Hydrograph analyses
• GIS-based soil and sediment layers
• Post-fire hydrology guidance
• Updated detention basin criteria consolidated into a single combined Hydrology Manual
Because hydrology practices and supporting datasets will continue to evolve, future revisions to the Hydrology Manual will be required periodically. These revisions will be implemented on an ongoing, as-needed basis and made publicly available. To ensure timely updates and administrative efficiency, authorization is requested for the Director of the Department of Public Works or the Chief Flood Control Engineer to approve future revisions to the Hydrology Manual.
Collectively, these updates will provide clearer, more transparent hydrology tools, improve consistency in hydrologic analyses Countywide, and better support development review, capital projects, and flood risk management efforts across San Bernardino County.
The updates to the existing Hydrology Manual were reviewed under the California Environmental Quality Act (CEQA) and determined to meet the criteria for the commonsense exemption under CEQA Guidelines Section 15061(b)(3), which applies when a project has no possibility of causing a physical change in the environment. The Hydrology Manual update also meets the exemption criteria under CEQA Guidelines Section 15378(b)(2) and 15378(b)(5), which identify administrative activities and general policy updates that do not result in direct or reasonably foreseeable indirect physical environmental impacts.
PROCUREMENT
Not applicable.
REVIEW BY OTHERS
This item has been reviewed by County Counsel (Sophie A. Curtis, Deputy County Counsel, 387-5455) on February 25, 2026; and County Finance and Administration (Kathleen Gonzalez, Administrative Analyst, 387-5412) on March 6, 2026.