West Weaver Creek FPIP at Oregon Street, Trinity County

5C Program's Stormwater Management Handbook-
A vegetated swale can be an aesthetically pleasing way to convey water around a site and protect downstream waterwaysThe purpose of the 5C Program's Stormwater Management Handbook is to provide a user-friendly, guide outlining best management practices for managing stormwater so that it has minimal impacts on watershed health and salmon populations. The target audience includes landowners, county planning departments, and the general public. As with any 5C product, whether county planning departments use the Handbook, and if so, to what extent, is up to each individual county; the Handbook is available for their reference. Periodic updates and revisions are anticipated based on feedback and monitoring.

What is Low Impact Development?

Low Impact Development (LID) is a collection of methods (aka Best Management Practices or BMPs) that preserve natural resources and collect and clean stormwater runoff to protect and improve water quality and availability. One of the main principles is to simulate natural drainage patterns and incorporate vegetation and natural materials into stormwater facilities. The Puget Sound Partnership defines LID as "a stormwater and land use management strategy that strives to mimic pre‐disturbance hydrologic processes of infiltration, filtration, storage, evaporation and transpiration by emphasizing conservation, use of on‐site natural features, site planning, and distributed stormwater management practices that are integrated into a project design." LID may also be referred to as Green Infrastructure, Green Development Practices, or Alternative Storm Water Management Systems.

Pervious pavement (left side) and traditional impervious pavement (right side).  Areas of pooled water are seen on the impervious surfaceThere are over 200 best management practices (BMPs) that may be used to improve watershed health. BMPs may fall into two categories:

Non-structural BMPs
These are restoration and protection practices often employed during the early planning phase, but may also appear during other project phases. This includes choosing low impact techniques over conventional ones and also selecting natural approaches over ones that require more physical structures.
- Relative Effectiveness: High
- Relative Cost: Low

Structural BMPs
These are mitigation strategies or facilities designed to reduce impact from either past or future development.
- Relative Effectiveness: Low to Moderate
- Relative Cost: High


Why Use Low Impact Development?Rock swale conveys water from a downspout

In undeveloped areas, very little rainwater or snowmelt runs off the land like it does in urbanized towns and cities. Trees, plants, and soil capture much of the precipitation, and some of it evaporates back into the air. Most of the precipitation that doesn't evaporate or get captured by vegetation soaks into the ground where soil and microbes remove pollutants naturally. The water slowly recharges streams, wetlands and groundwater. Very little runs off, except in very large storms. The natural terrain acts like a sponge.

This natural hydrologic cycle is radically altered when land is developed and the way it has been for decades is changed. Typical development clears the land of vegetation and covers it with hard surfaces such as roads, parking lots, and rooftops. Construction and foot traffic compact soils, so that even landscaped areas can generate unnaturally high runoff volumes. Storm drains are installed to get water out of the way by sending it into local streams or injecting it underground without treatment. Development dramatically increases runoff volumes. Even when controlled by detention basins, this causes flooding, damages fish and wildlife habitat, and delivers pollutants such as oils and pesticides to local waterways. The decreased infiltration results in: less cool, clean groundwater to recharge streams in the dry summer months; and in a reduction in water availability throughout the watershed. LID practices may be incorporated into existing as well as newly built developments in a community. They increase groundwater supplies and reduce the negative water quality impacts to streams and fish habitat, flooding, and in many cases, the cost of stormwater treatment and infrastructure. They are aesthetically pleasing and have been shown to increase real estate values.


Navigating the 5C Program's Stormwater Management Handbook

The summary below outlines the available guidance on stormwater management through the 5C Program to help ensure that you have all the information you need to plan, design, construct, and maintain best management practices. You can navigate the material in a few different ways: by topic, by specific practice, or by the function you want to achieve.

By Topic

Guidance is organized by overarching topic. In each fact sheet, we've strived to create easy‐to‐understand text and illustrations on implementation, cost considerations, and relative benefits to watershed and water conservation efforts. In the table below, guidance is ordered by relative cost for new development. In retrofits, where stormwater management is not required, managing stormwater with Low Impact Development (LID) or even with conventional approaches will require an initial investment. However, there are many benefits of stormwater management that are not easy to quantify in dollars. Certain practices, such as those that capture stormwater, can actually save money in the long‐term. In some case, effectiveness will probably be the driving factor for decision‐making.
List of BMPs for 5C Program Stormwater Management Handbook
* This rating refers to the effectiveness of stormwater management. These techniques offer other benefits such as water conservation with a good rate of effectiveness.

List of supplemental information for 5C's Stormwater Management Handbook

Implement Specific Practices

If you're already pretty familiar with using best management practices or have something in mind already for other reasons, refer to the table below to see which guidance topics you'll need to gather before starting your project.

Table of BMPs by target practice or goal

Functional Checklist Approach

If you have some idea of what practices you'd like to use, but would like to explore additional approaches, then use this checklist approach below. Available resources are listed by how they work to protect watershed health. If best management approaches perform more than one function, they're listed in all relevant categories. Guidance that is essential or optional for implementation is listed with numbers corresponding to the topics table above.

Functional checklist and steps to take


Download/View the 5C Program Stormwater Management Handbook:

View each Chapter or download (pdf):

For more information, contact us

©2012. Five Counties Salmonid Conservation Program and Green Girl Land Development Solutions. The 5C Program Stormwater Management Handbook may be photocopied or reprinted in its entirety for noncommercial purposes.

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