Staff Report
City Council
Item No. 4.C
Meeting Date: May 13, 2026
From: John A. Corella, Director of Public
Works
Title: Ordinance to Amend Cathedral City
Municipal Code Chapter 8.24,
Floodplain Management, Including
Sections 8.24.10, 8.24.020, and
8.24.070
RECOMMENDATION:
Introduce and provide first reading, by title only, and waive further reading of an ordinance amending
Cathedral City Municipal Code Chapter 8.24,
Floodplain Management, including Section
8.24.010 Statutory Authorization, Findings of Fact,
Purpose and Methods, Section 8.24.020
Definitions, and Section 8.24.070 Storm Water
Storage Facilities.
BACKGROUND:
Chapter 8.24 of the Cathedral City Municipal
Code (CCMC) establishes the city’s floodplain
management framework, including but not limited
to drainage requirements and stormwater storage
obligations for new development and
redevelopment projects. The regulations were
originally adopted in 1991 and last
comprehensively amended in 2013. Since that
time, hydrologic science, regulatory requirements,
and stormwater management practices have
evolved.
At the federal and state levels, agencies such as
the Federal Emergency Management Agency
(FEMA), and the California State Water
Resources Control Board (SWRCB) have adopted
updated standards for floodplain management
and stormwater control. These standards
incorporate improved rainfall data and modern
design approaches that enhance public safety
and system resilience.
At the regional level, the Riverside County Flood
Control and Water Conservation District
(RCFCWCD) published its updated Hydraulic
Design Manual in March 2024. This manual
provides current guidance on hydrology, soil
classifications, runoff coefficients, and stormwater
detention and retention criteria routinely used in
local development projects.
Locally, Cathedral City has experienced more
intense storm events in recent years. Tropical
Storm Hilary (August 2023) delivered more than
three (3) inches of rain in a single day, which is
over half of the region’s average annual rainfall of
4.6 inches, resulting in widespread flooding and
mudflows. This event highlighted the need to
update the city’s
stormwater design standards.
In addition, city staff regularly review development projects that incorporate modern stormwater retention systems, such as underground storage chambers, infiltration systems, and controlled release facilities. These systems are not clearly addressed in the current code, resulting in project-specific interpretations, repeated exception requests, and delays in plan review and project approval.
DISCUSSION:
Amendments to Chapter 8.24 are necessary to modernize the city’s floodplain management regulations and align the municipal code with current engineering standards and regulatory requirements.
The proposed ordinance amends the following sections of Chapter 8.24:
Section 8.24.010 - Statutory Authorization, Findings of Fact, Purpose and Methods Section 8.24.020 – Definitions
Section 8.24.070 – Storm Water Storage Facilities
Section 8.24.010 (Statutory Authorization, Findings of Fact, Purpose and Methods) This amendment adds a new subsection titled General Drainage Law Principles, which codifies fundamental upstream and downstream drainage responsibilities. The provisions clarify that downstream properties must accept natural drainage flows from upstream areas, upstream properties may not concentrate or redirect runoff without proper conveyance, and property owners may not obstruct or divert natural drainage features without providing adequate drainage facilities. These provisions establish clear expectations for drainage responsibilities and reduce ambiguity during project review. The proposed changes are shown in Exhibit A of Attachment 2 (redlined version).
Section 8.24.020 (Definitions)
This amendment updates and expands key definitions to reflect current floodplain management and stormwater engineering terminology. New and revised definitions include controlled bleed-off, freeboard, infiltration rate, tributary drainage area, historic drainage relief routes, underground storage chambers, and the distinction between local and regional stormwater facilities. These updates improve clarity, consistency, and enforceability of the code during plan review and project design. The proposed changes are shown in Exhibit B of Attachment 2 (redlined version).
Section 8.24.070 (Storm Water Storage Facilities)
This section is comprehensively updated to reflect current stormwater design standards and practices. The amendments incorporate NOAA Atlas 14 rainfall data and establish an updated design storm methodology. The proposed revised standards establish that the required design storm is the 100-year storm event, evaluated over the one-hour, three- hour, six-hour, and twenty-four-hour durations, that produces the maximum required storage volume in the detention or retention basin, accounting for infiltration and other basin outflows.
Additionally, design and performance standards for detention and retention facilities are clarified, including requirements for drawdown times, freeboard, depth and slope limitations, and provisions for fencing, access, and maintenance. Controlled bleed-off criteria are updated based on development size and downstream capacity, and enhanced safety measures address energy dissipation, clogging considerations, ADA compliance, and basin depth markers.
The revisions also require consideration of upstream historic flows and downstream impacts, and clearly assign developer responsibilities for drainage, overflow routing, and long-term maintenance. In addition, standards for regional stormwater facilities are established to align with current engineering practices. These updates provide clear and enforceable design criteria. Due to the technical nature and extent of the revisions, all changes are shown in Exhibit C of Attachment 2 (redlined version).
City staff developed these amendments in coordination with Christiansen and Company, Fomotor Engineering, and NAI Consulting, Inc., both of which provide on-call plan check services. This collaboration ensured that the updates address practical challenges encountered during development review and improve consistency and efficiency in the plan check process.
Summary of Proposed Amendments
The proposed ordinance updates hydrology and design criteria to reflect current data and engineering standards, clarifies and expands definitions to ensure consistent application, establishes clear and enforceable stormwater design requirements, and differentiates between local and regional stormwater facilities. Collectively, these changes improve public safety, reduce flood risk, and provide greater clarity and predictability for development review.
Staff recommend that City Council introduce and provide first reading, by title only, and waive further reading of an ordinance amending Cathedral City Municipal Code Chapter
8.24, Floodplain Management, including Section 8.24.010 Statutory Authorization, Findings of Fact, Purpose and Methods, Section 8.24.020 Definitions and Section 8.24.070 Storm Water Storage Facilities.
FISCAL IMPACT:
There is no direct fiscal impact associated with the adoption of the proposed ordinance, aside from staff time and the use of the Engineering Department’s on-call consultants who assisted in developing these changes. Fees for their services are already included in the Engineering Professional and Technical Services budget under previously approved Task Orders for plan-checking services.
FIVE-YEAR STRATEGIC PLAN:
Goal C- Fiscal Stability and Sustainability
Objective: Cathedral City has economically prospered by facilitating the investment of private dollars in high quality development which benefits the community. We remain fiscally solvent by instituting prudent fiscal policies and transparent financial practices.
Action Item C-6: Implement a private development entitlement and plan review system which is predictable, streamlines internal intake and review processes, and creates applicant experiences which are facilitative vs regulatory.
ATTACHMENTS:
1. Ordinance No____ Amending CCMC Chapter 8.24
2. Redline of Ordinance Exhibits