Environmental Rules in Colusa County, CA (2026)
4 rules for unincorporated Colusa County, California.
Verified from official government sources
Stormwater Management
In unincorporated Colusa County, agricultural-zone development that needs a permit or administrative permit must produce no net increase in off-site drainage flows, including peak flows during a storm event, and must include water quality measures that reduce stormwater pollutants under Zoning Code Section 44-2.20.20(B)(e).
Colusa County Stormwater Drainage Rules
Some RestrictionsColusa County Zoning Code § 44-2.20.20(B)(e)
B. Performance Standards. The following performance standards apply to permitted uses and uses allowed with an administrative permit in the agricultural zones as required in Table 44-2.20-2. Projects that cannot meet the following performance standards shall be elevated to a Minor Use Permit. ... Drainage and water quality. There shall be no net increase in off-site drainage flows, including pe...
Erosion Control
Grading or development on natural slopes over 15 percent anywhere in unincorporated Colusa County must follow the erosion-control standards in Zoning Code Section 44-5.40.050: cut slopes capped at two-to-one, cuts over 16 feet discouraged, and graded slopes revegetated to hold soil in place.
Colusa County Hillside Grading Erosion Rules
Some RestrictionsColusa County Zoning Code § 44-5.40.050
44-5.40.050 Grading Standards. Grading shall respect the natural contour of the existing terrain wherever possible. B. ... Cuts in excess of 16 feet in height from top to toe shall be discouraged. C. ... Where grading is necessary, the principles of contour grading should be employed: 1. Cut slopes shall not exceed two horizontal to one vertical (2:1). Shallower slopes may be required if indica...
Flood Zones
Unincorporated Colusa County applies a dedicated Flood Management (F-M) zoning classification, under Zoning Code Section 44-2.60.10(B), to land outside river channels that has flooded before and could flood again. The F-M zone limits new development to agricultural and resource-management uses that will not block flood flows, and Table 44-2.60-1 caps structure height and sets a 1-acre minimum parcel size.
Colusa County Flood Management Zone Rules
Significant RestrictionsColusa County Zoning Code § 44-2.60.10(B); Table 44-2.60-1
B. Flood Management (F-M). The F-M zone is intended to be applied to areas other than River Frontage areas which have been inundated by overflow floodwaters in the past, and which may reasonably be expected to be inundated by such floodwaters in the future. The Flood Management zone is intended to limit the use of areas subject to such inundation and flooding to protect lives and property from ...
Defensible Space
Unincorporated Colusa County's Zoning Code ties its landscaping standards to state defensible-space law. Section 44-3.10.020(F) requires a defensible space or zone around a building or structure under Public Resources Code Section 4291(a) and (b) for qualifying landscape projects, and directs that fire-prone plants and highly flammable mulches be avoided in fire-prone areas.
Colusa County Defensible Space Requirement
Some RestrictionsColusa County Zoning Code § 44-3.10.020(F)
F. Public Safety. Plant species should be selected and located so that at maturity they do not interfere with pedestrian, bicycle, or vehicular circulation and do not conflict with overhead lights or utility lines. Landscaping in fire-prone areas should address fire safety and prevention. A defensible space or zone around a building or structure is required per Public Resources Code Section 429...
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