Table of Contents
Overlay zoning can be tailored to local conditions, which makes it an effective tool for addressing natural hazards. Overlay zoning typically is used in areas with flood, wildfire and geologic (steep slopes) hazards. The overlay zone district is often named for the type of natural hazard it is regulating, e.g., Hillside Protection Overlay or Floodplain Overlay District. Key elements of an overlay zone district include:
- Purpose
- Applicability
- Overlay district map
- Development standards
- Review procedures
The following sections describe each of these common elements and provide standard language that can be considered by Colorado local governments. Model language is in gray shading. Commentary is located in italics in the column at the right. The model language used in this document is based on several existing ordinances from varying communities around the state, including municipalities and counties. The language is illustrative only; consult local counsel to tailor language for your jurisdiction.
Typical Hazards Addressed by Overlays: The natural hazards most typically addressed with overlay zoning are flood, wildfire and steep slopes. Overlay zones can also be used to address other natural hazard risks or sensitive lands such as mapped avalanche zones, unstable soil conditions, dipping bedrock, wetlands or riparian corridors.
A. The purpose of the [name] Overlay District is to promote the public health, safety and welfare of the citizens of [name of local government]; minimize the risk of loss of life and property due to [natural hazard]; encourage and regulate prudent land use; permit only such uses that will minimize the danger to the public health, safety, welfare and property; reduce the demands for public expenditures for disaster relief, hazard mitigation, and protection of structures and facilities permitted in the underlying zone district(s); and regulate buildings and structures so as to minimize the hazard to the public health or property.
B. Furthermore the [name] Overlay District implements the following goals and policies of the [name of local government] Comprehensive Plan: [relevant goals and policies]
Purpose: The purpose statement articulates the intent for the overlay district and identifies what is being regulated through the overlay standards. It should communicate why the overlay zone district was created and can identify the goals and objectives of local planning documents it is intended to implement.
A. The provisions and regulations of this section shall apply to all lands within [name of local government] designated a [type of natural hazard/sensitive land] as identified by the official map for the [type of natural hazard/sensitive land] Overlay District.
B. Uses permitted by the underlying zoning district are allowed unless specifically prohibited and provided that the proposed use complies with the standards and submittal requirements of this section.
C. All land use activities and development requiring a development, building, grading or other land use permit, are subject to the provisions of the [type of natural hazard/sensitive land] Overlay District as identified by the official map.
D. If a structure, lot, or other parcel of land lies partly within the [type of natural hazard/sensitive land] Overlay District, the part of such structure, lot, or parcel lying within the Overlay District shall meet all requirements for this district as set forth in this section.
The [type of natural hazard/sensitive land] Overlay District Map is hereby incorporated by reference and shall be maintained by the [name of local government] [Planning Department].
In cases where a boundary or the severity of conditions at a specific location within the Overlay District are disputed, the land owner of the property where the boundary is in dispute shall be given a reasonable opportunity to present their case to the [Director of Planning or Administrator] and shall submit technical evidence to support such dispute. The [Director of Planning or Administrator] shall not allow deviations from the boundary line as mapped unless technical and geological evidence clearly and conclusively establish that the map location of the line is incorrect, or that the designated hazard conditions do not present a significant hazard to public health, safety, or to property at the specific location within the hazard area boundary for the particular proposed land use.
Overlay District Map: The natural hazard areas that are being regulated by the overlay zone district should be mapped based on reliable technical data. Official maps produced by state or Federal agencies, such as the Colorado Geological Survey or Federal Emergency Management Agency, can be adopted by the local government as official maps to define an overlay district. The maps need to be available for public reference at the local government offices and online if possible.
This section should contain the substantive requirements that a proposed land use or development must comply with in order to meet the community’s goals for the overlay zone district. This can include standards for building bulk, height, site layout, impervious surface area, specific construction methods, grading, vegetation and landscaping requirements, and special standards for public infrastructure such as roads and water systems. The required standards must directly relate to mitigating the risks posed by the natural hazard or the protection of sensitive lands.
Development Standards: Identify possible development standards and narrow this list to those likely to be effective in the local community at achieving desired outcomes. The community may already have standards in existing development and engineering manuals that address steep slopes, soil conditions and flooding that can be made specific to natural hazard overlay districts.
A. General Standards
- The provisions of this Overlay District shall apply in addition to the applicable requirements of the underlying zoning district. When the standards of this Overlay District conflict with any other provision of the [code/ordinance], this Overlay District shall control.
- Development determined to be subject to the provisions of the [type of natural hazard/sensitive land] Overlay District shall be required to mitigate identified hazards through compliance with and utilization of the [name of local government] development standards listed below, and may require the implementation of a Mitigation or Management Plan specifically addressing the natural hazard conditions of the subject property.
- Additional measures aimed at reducing the risk of [type of natural hazard/sensitive land] may be imposed at the discretion of the [Chief Building Official or approval body] for the type of development being proposed.
B. Development Standards: All land use activity and development must comply with adopted [name of natural hazard] mitigation standards (such as floodplain regulations, or a hillside protection ordinance) in addition to the applicable requirements of the underlying zoning district. When these requirements conflict with any provision of the underlying zone district, the provisions of [type of natural hazard/sensitive land] Overlay District shall control. The types of mitigation measures required are as follows: (Note: The model language below is an example for a wildfire hazard overlay zone district.)
1. Wildfire Mitigation and Forest Management plan prepared by a professional forester, including but not limited to:
a. Identification of fuel type as related to slope and aspect
b. Reduction of fuel loading on-site
c. Existing condition of current vegetation
d. Recommendations to improve vegetative condition
2. Roads, streets and driveways designed for safe access for emergency fire equipment and evacuation.
3. Road, street, building, and emergency access signage designed for clear visibility from public roads.
4. Emergency water supply appropriate for the type and location of development proposed as determined by the [Chief Building Official, Public Works Director, or Administrator] in conjunction with the Fire Department.
5. All forms of development located, designed, and constructed in a manner to minimize ignition from a wildfire and the spread of fire from structures to wildland areas and/or structure to structure.
Mitigation Standards Manual: Douglas County adopted a Wildfire Mitigation Standards manual that sets forth all requirements for site layout and building construction in its Wildfire Overlay Zone District. Adopting standards outside the zoning code allows the standards to be more easily updated as new construction techniques and fire-fighting methods are developed.
This section describes the submittal requirements and review procedures for the [type of natural hazard/sensitive land] Overlay District.
A. Submittal Requirements: These submittal requirements are in addition to the underlying zoning district submittal requirements for the type of land use activity or development proposed. The following information must be included in all applications for development or land use activity: (Note: The model language below is an example for a wildfire hazard overlay zone district.)
- A description of the existing site characteristics including vegetative, topographical, and other pertinent environmental conditions.
- A determination by a professional forester or qualified wildfire interface fire specialist as to whether the site characteristics constitute a hazard conducive to wildfire.
- An assessment of the severity of the wildfire hazard and implications of future development relative to the protection of life-safety and resource protection.
- An analysis of the intensity and character of existing and proposed development and its effect on the hazard.
- An analysis of the relationship between the proposed development and the hazard both inside and outside the proposed development.
- Recommendations pertaining to the form, type, and extent of required mitigation measures and how the proposed mitigation measures meet the standards and provisions of this Overlay District.
- A site plan detailing the recommended mitigation measures incorporated into the proposed development.
- A Hazard Mitigation or Management plan if determined necessary by the [Planning Director].
B. Review Procedures: The review procedure for the provisions of this Section will coincide with the review procedures for the type of development or use proposed and the requirements of the underlying zoning district.
- Land use activity or development in the [type of natural hazard/sensitive land] Overlay District shall be determined based on the evidence and information required by this Section.
- The approving body for the type of development application being processed in the [type of natural hazard/sensitive land] Overlay District shall approve, approve with conditions, or deny the requested development activity.
- Additional conditions for approval may include, but are not limited to, the following:
a. Alteration of the physical characteristics or vegetative features of the land;
b. Construction standards required for proposed structures;
c. Construction standards for roads;
d. Design and density within the proposed development; and
e. Location of structures, uses, or other improvements within the proposed development.
Submittal Requirements and Review Procedures: Review and approval procedures for development in an overlay district should be concurrent with all other review processes required for the proposal.