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DRN-005 Waterway Setback Requirements

Revised 01/31/2019

This document summarizes waterway setback information from assorted sections of the Sonoma County Code (SCC). When multiple setbacks apply to a waterway, the most protective setback shall generally govern land use and development.

Purpose

To provide information regarding various setbacks to waterways.

Background

The County of Sonoma has established various types of setbacks from different types of waterways in order to protect life, property, and the environment. Setbacks from waterways are also necessary to account for the natural meandering of streams and to provide sufficient maintenance access between property and streams. This document summarizes waterway setback information from assorted sections of the Sonoma County Code (SCC). When multiple setbacks apply to a waterway, the most protective setback shall generally govern land use and development.

Definitions

Designated Stream
includes all streams shown on the General Plan Open Space maps. These streams are commonly referred to as “blue-line streams”. The Riparian Corridor (RC) zone is applied to all designated streams and adjacent streamside conservation areas.
Lake (SCC §11.22.020)
means a permanent natural body of water, or an artificially impounded body of water, isolated from the sea, with at least one (1) acre of open water of sufficient depth and permanency to prevent complete coverage by rooted aquatic plants.
Pond (SCC §11.22.020)
means a body of still freshwater smaller than a lake, often artificially impounded.
Reservoir (SCC §11.22.020)
means a water storage structure made by constructing a dam, embankment, or pit with an impermeable liner such as clay or synthetic material.
Stream (SCC §7-19-(t) and SCC §11.22.020)
means any natural channel with bed and banks containing flowing water or showing evidence of having contained flowing water, such as deposit of rock, sand, gravel or soil. Stream includes creeks and rivers.
Wetland (SCC §11.22.020)
means land transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. A wetland must have one (1) or more of the following three (3) attributes in the Coastal Zone, and two (2) or more of the following three (3) attributes in all other parts of the unincorporated area of the county:
  1. At least periodically, the land supports predominantly hydrophytes (plants specifically adapted to live in wetlands).
  2. The substrate is predominantly undrained hydric (wetland) soil.
  3. The substrate is saturated with water or covered by shallow water at some time during the growing season of each year.

General

The following flow chart shall be used as a general guide to determine applicable stream setbacks.

  1. Stream Setbacks for Structures (SCC §7-14.5)

    All structures requiring a building permit or an agricultural exemption shall be set back from streams, as measured from the toe of the stream bank outward, a distance of 2.5 times the height of the stream bank plus 30 feet or 30 feet outward from the top of the stream bank, whichever distance is greater, unless a greater distance is established in the General Plan, Local Coastal Plan, and/or Zoning Code. If the top of the stream bank cannot be determined by visual analysis, it shall be determined by hydraulic analysis as the water surface elevation for the 100-year storm event plus 1.5 feet. Stream bank height is the change in elevation from the top of bank and the lowest toe of bank. See Figure 1 for graphical examples of stream setbacks for structures. For questions regarding stream setback requirements for structures, please visit or call Permit Sonoma’s Building Plan Check customer service cubicle at (707) 565-2095.
Figure 1: Graphical Examples of Stream Setbacks for Structures
Images depicting setback from stream to building setback line (BSL) with various slopes and topography. a) Bank Slope Steeper Than 2.5:1. b) Bank Slope Flatter Than 2.5:1. c) Bank Slope Equal To 2.5:1. d) Irregular Slope Steeper Than 2.5:1. e) Irregular Slope Flatter Than 2.5:1. f) Undefined Top of Bank
View Full Size Image
  1. Stream Setbacks for Riparian Corridors (SCC §26.65.030)

    The Riparian Corridor (RC) combining zone includes the stream bed, bank and adjacent streamside conservation area on each side of a designated stream as measured from the top of the higher bank. Land uses and development, including grading, vegetation removal, agricultural cultivation, structures, roads, utility lines, and parking lots, is prohibited within the Riparian Corridor, except as allowed by SCC §26.65.030 and 26.65.040. The minimum setback for development and agricultural cultivation is indicated by the zoning for each property. For example, a parcel zoned “RC 100/50” indicates that there is a 100 feet setback for development and a 50 feet setback for agricultural cultivation. Zoning information is available online at:
  2. For questions regarding setbacks for riparian corridors, please contact Permit Sonoma’s Planning Division at (707) 565-1900, option 5.
  3. Stream Setbacks for Septic Systems and Water Wells

    1. Stream Setbacks for Septic Systems (Sonoma County Onsite Wastewater Treatment Systems Regulations and Technical Standards). Septic systems shall be setback 50 feet from the top of ephemeral stream banks and 100 feet from the top of perennial stream banks.
    2. Stream Setbacks for Water Wells (SSC §25B-6.b). Wells shall be setback 30 feet from the top of stream banks.
  4. For questions regarding stream setback requirements for wells and septic systems, please visit or call Permit Sonoma’s Well & Septic customer service cubicle at (707) 565-2849.
  5. Stream and Water Feature Setbacks for Grading Work

    1. Stream Setbacks for Grading Work (SCC §11.14.100). Grading work and land disturbance shall be set back 25 feet from top of stream banks, unless a greater setback is required by general plan, local coastal plan, or zoning code.
    2.  Setbacks for Grading Work near Lakes, Ponds, and Reservoirs (SCC §11.14.090). Grading work and land disturbance shall be set back 50 feet from the high water mark of lakes, ponds, and reservoirs, unless a greater setback is required by general plan, local coastal plan, or zoning code.
    3. Setbacks for Grading Work near Wetlands (SCC §11.14.110). Grading work and land disturbance shall be set back from wetlands in compliance with the requirements in Table 1, unless a greater setback is required by general plan, local coastal plan, or zoning code. These setback requirements shall not apply where all necessary state and federal permits, approvals, authorizations to fill wetlands are obtained.
Type of WetlandSetback
Wetlands des­ig­nat­ed in zoning code100 feet from the delineated wetland boundary
All other wetlands50 feet from the assessed wetland boundary, unless the wetland assessment recommends a greater or lesser setback

Existing vegetation shall be retained in setback areas to filter soil and other pollutants carried in storm water. Vegetative filter strips may be installed in setback areas in compliance with Permit Sonoma’s best management practices guide to enhance filtration. For questions regarding waterway setback requirements for grading work, please visit or call Permit Sonoma’s Engineering customer service cubicle at (707) 565-2268.

Approval: Alex Rosas, Engineering Division Manager

Revision: 01/31/2019, 07/11/2017

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