Stormwater Management Manual
II. GOALS AND POLICIES
This chapter states the overall goals and general principles and policies of the Flood Control District regarding stormwater management. These goals, principles and policies were developed in cooperation with City and County staff and elected representatives, and representatives of the private engineering and development communities.
The goals, principles and policies presented in this chapter provide direction for stormwater management strategies and practices. They are implemented, in turn, by technical criteria and data in the manual.
- Provide protection from periodic inundation which could result in loss of life and property.
- Protect and enhance natural resources belonging to the stream environment.
- Prevent significant erosion and adverse effects on water quality.
- Provide a regional approach to stormwater management which is both internally consistent and consistent with other community goals and plans.
- Achieve maximum use of resources through multiple compatible uses.
- Assure orderly growth and development and minimize its adverse effects.
B. Principles and Concepts
The following principles are broad, basic concepts which underlie policies and related criteria.
- The provision of adequate stormwater management facilities and programs is necessary to preserve and promote general health, welfare, and economic well-being.
- Future problems can be minimized or avoided if jurisdictions in a watershed agree to common standards, methodologies, and criteria pertaining to control of runoff and land development.
- Every parcel of land is part of and contributes runoff to that of a larger watershed. This cumulative characteristic of runoff makes it advisable to formulate strategies that are coordinated, integrated, and balanced on a regional level if effective results are to be achieved.
- Both the public and individual property owners share responsibility for stormwater management.
- Effective stormwater management requires a land use commitment. Stormwater management competes for space with other land uses. If adequate provision is not made in a land use plan, stormwater run-off may conflict with other land uses and result in water damages and impair or disrupt the functioning of other systems.
- A stormwater management strategy must consider multiple means of accomplishing its objectives. In general, there is not a single, all-encompassing method or design: every site or situation presents a unique mix of scale, resources, land use constraints, and environmental setting.
- It is essential to distinguish between levels of objectives in drainage systems. These two levels are commonly referred to as the minor function and the major function. The minor function is usually to limit disruption and to minimize inconveniences resulting from more frequently occurring, less significant storms. Storm drain systems consisting of underground pipes are commonly used to provide the minor function.
The major function is to prevent or minimize property damage, injury, and loss of life during infrequent, major storms.
- The financing of stormwater management systems is fundamentally the responsibility of the affected property owners -- both the person directly affected by the water and the person from whose land the water flows. However, there is a public interest involved because of the potential demand for disaster relief.
- Floodwater management, treatment of runoff for water quality protection, and protection of riparian environmental resources are not necessarily conflicting and may be complementary.
- A program for collecting and analyzing basic data is essential in developing effective stormwater management strategies and monitoring their performance. In the long term, significant cost savings can also be realized by avoiding oversized systems. Further, monitoring may be a requirement for compliance with regulatory programs.
- Flood preparedness, warning and response programs are important in reducing loss of life, injury, property damage, and disruption due to flooding.
- Design Criteria
a. Storm drainage planning and design in Western Placer County shall adhere to the criteria presented in this manual. Governmental agencies and engineers shall utilize the manual in the planning of new facilities and in their reviews of proposed works by developers, private parties, and other governmental agencies, including the California Department of Transportation, other elements of the State Government and the Federal Government.
However, none of the criteria or guidelines are intended to substitute for the sound application of fundamental engineering or scientific principles or to conflict with stated goals and policies.
b. The design criteria in this manual shall be revised and updated as necessary to reflect advances in stormwater management concepts and technology.
- Level of Protection
a. The 100-year flood shall be the criterion for measures intended to minimize property damage, injury, and loss of life.
- Transfer of Problems
a. Improvements of any kind shall not transfer a problem from one location to another except when the transfer is part of a regional solution to flood problems.
b. Channel modifications which create problems downstream shall be avoided. Potential problems include erosion, downstream sediment deposition, increase of runoff peaks, and debris transport.
c. Diversions from one watershed to another shall generally be avoided. The diversion of storm runoff from one watershed to another may introduce significant legal problems.
d. All land development proposals shall be evaluated for their effects on runoff and flooding, both offsite and onsite.
- Floodplain Management
Floodplain management is an important component of overall stormwater management strategies.
a. Local jurisdictions are encouraged to adopt and implement measures which will lessen the exposure of property and facilities to flood losses, improve the long-range land management and use of flood-prone areas, and inhibit, to the maximum extent feasible, incompatible development and encourage compatible uses in such areas. Compatible uses are those which do not reduce instream flood storage, create higher flood elevations, or adversely effect riparian or aquatic resources. Compatible uses can include open space, parks and recreation, and agriculture.
b. Floodplain designations should account for future development.
c. Flood plains should be delineated along all significant streams in areas which are developing. These delineations should make full use of the Corps of Engineers Flood Plain Information Studies, U.S. Geological Survey Flood Plain Maps, and floodplain studies by private consulting engineers and engineers of the Federal Emergency Management Agency.
d. Floodplain information will be reviewed and updated as necessary and appropriate to reflect changes due to urbanization, changed conditions, and new information, including the occurrences of extraordinary hydrologic events.
e. Floodplain boundaries shall be shown on preliminary and final subdivision plats, and the area inundated should be indicated as a flow easement or dedicated in fee. This would encompass even the smaller streams which are often overlooked even though they may have a large flood damage potential.
f. Information on floodplain elevations and boundaries shall be collected and stored in a central place by the jurisdiction and made available to all planners, developers, and engineers.
g. General and specific plans should require compatible uses in the 100-year floodplain and require easements to facilitate effective floodplain management.
- Natural Streams
a. Natural drainage ways shall be used for storm runoff whenever possible. The environmental value of natural channels is clear. Natural channels are also valuable in controlling storm runoff because vegetation and irregular sections and alignments of natural channels dissipate energy, thereby slowing the runoff. Furthermore, the floodplain typically provides temporary storage of floodwaters which attenuates flood peaks as they pass through the channel reach.
b. Local jurisdictions shall not permit loss of storage in the 100-year floodplain of designated regional streams except when necessary to protect existing structures or improvements from flood damages or to provide for improvements which have greater overall public value. Changes shall be allowed in the floodplain in association with compatible uses so long as the changes involve no net loss of storage. For example, minor grading and earthworks could be permitted on broad floodplains in order to develop parks and recreational facilities.
c. Local jurisdictions shall not permit straightening, widening, or smoothing of designated regional stream channels except as necessary to protect existing structures or improvements from flood damages or to provide for improvements which have greater overall public value. However, changes in the channel which restore, improve or enhance the desirable flood control properties shall be allowed and are encouraged.
d. The Flood Control District shall develop comprehensive plans and criteria for the maintenance of designated regional stream channels. In order to maintain their effectiveness, natural streams must be managed. Erosion, widening and meandering stream alignments are natural processes which may be accelerated by increased runoff due to development. Over time, selective improvements such as drop structures and bank protection may be required to help stabilize channels at specific locations to protect structures and public facilities. Vegetation may be used to help stabilize channels as well.
Irrigation flows and runoff in the summertime can cause excessive growth of vegetation which must be removed, especially in smaller streams. Sedimentation can also create localized problems.
e. Local jurisdictions and individuals are encouraged to follow Flood Control District plans and criteria for the maintenance of designated regional stream channels.
- Multipurpose Use
Opportunities for multipurpose use of facilities to achieve drainage goals will be considered. The many competing demands placed upon water and funds suggest that a strategy for managing runoff be as multipurpose as practical. Stormwater management facilities can fulfill a number of other purposes, and facilities not designed primarily for stormwater management frequently can be designed to provide runoff management benefits; e.g., parks or golf courses can provide temporary storage of peak flows. The land areas required for controlling the 100-year or even 10-year flood are infrequently used. Given the scarcity of water, land and funding for facilities, it makes sense to consider multipurpose use.
- Basin Master Plans
a. Master plans will be prepared as soon as possible for each drainage basin.
b. Regional master plans will be prepared by the Flood Control District.
c. Each municipality in Placer County is responsible for detailed master plans in its jurisdiction. The Flood Control District will coordinate the local plans to assure consistency with the regional plans.
d. All individual land development proposals shall be reviewed for compatibility with master plans.
e. Master plans shall be consistent with other elements of general plans. Drainage is an interrelated component of the total community infrastructure. General plan policies must be considered in order to be effective and avoid conflicts or impacts on other elements.
- Flood Preparedness, Warnings, and Response Planning
a. The Flood Control District shall assist local jurisdictions and the Placer County Office of Emergency Services in the preparation of flood warning and response plans.
b. The Flood Control District shall assist local jurisdictions in the planning, implementation, and operation of flood warning systems.
c. The Flood Control District shall provide advise and consultations to local jurisdictions and the Placer County Office of Emergency Services in evaluating imminent or ongoing flood events.
d. The Flood Control District shall develop, publicize, and provide guidelines for flood preparedness and response.
e. Local governments are encouraged to develop community preparedness plans. These plans will make effective use of flood warnings in mobilizing community resources to prepare and adjust for flood conditions.
- Water Quality
a. The Flood Control District shall compile, evaluation and incorporate in this manual policies, criteria and guidelines for the planning and development of systems for the treatment of runoff to protect water quality.
b. The Flood Control District shall provide a regional forum to facilitate and participate in the development of programs and plans to satisfy the requirements of the Federal Non-Point Discharge Elimination System (NPDES) permit.
c. The Flood Control District will incorporate final rules and regulations when plans for nonpoint source management have been approved by the EPA and California State Regional Water Quality Control Board.
- Data Collection
a. Flood damage data will be collected in a systematic and uniform manner. A systematic and uniform method of appraising direct and indirect damages assures comparability of data.
b. A comprehensive program to collect data and analyze rainfall-runoff relationships shall be developed and maintained.
c. The magnitude of computed and measured runoff peaks shall be tabulated for regional streams so that comparisons may be readily made between basins, erroneous (or at least differing) values may be identified, and the effects of development may be determined.
d. The Flood Control District shall archive and maintain all pertinent data developed during the master plan process and make it available to all affected parties. This data would include maps, map overlays, reports, and hydrologic and hydraulics models.
e. The Flood Control District shall acquire and actively maintain a Library which shall be available for use by all governmental units and practicing planners and engineers.
- Adoption of Manual
a. This Manual shall be adopted by all jurisdictions in the county.
b. The review and adoption process for this Manual will include both public and private interests.
c. This Manual will be the basis for all master drainage plans and the Flood Control District's review of all local drainage plans.
d. The Flood Control District will present the Manual to all appropriate State and Federal Agencies for review.
e. The Flood Control District will provide technical assistance to both public and private entities to increase local capabilities in drainage planning and design.
f. Implementation of the Manual shall be supported and promoted by the staffs of participating jurisdictions.
a. Problems encountered in application of this manual shall be reviewed by the Flood Control District to determine whether it indicates a need for a new or different policy, practice, or procedure.
b. The Flood Control District's Technical Advisory Committee shall continually review needs and shall recommend changes as necessary in this Manual.
c. Any person finding errors, misconceptions, or proposing improvements to this manual is requested to contact the Flood Control District Engineer.
d. Amendments or additions to goals or policies in the Manual shall be approved by the District's Policy Advisory Committee and Board of Directors.
e. Amendments or additions to portions of the Manual other than goals or policies may be approved by the Director with the recommendation of the District's Technical Advisory Committee.