During the new development process, stormwater policy guides what practices are built and how they are designed. The Walnut Creek Watershed Management Plan recommends updating these policies to increase the standards guiding this process. New standards would have numerous benefits including:
- It is expected that successful implementation of these policies could reduce runoff volumes from suburban development areas by approximately 45% during a 1-year return period storm event (2.67” in 24 hours). This would be a volume reduction of 17,600 gallons per acre drained for that event.
- Runoff reduction from areas developed using these policies during the 100-year return period storm event (7.12” in 24-hours) would be expected to be approximately 20%, compared to sites without soil quality restoration. This would be a volume reduction of 33,400 gallons per acre drained for that event.
- Total pollutant loading would be expected to be reduced by at least an amount similar to runoff volume reductions.
- Reduced need for irrigation and fertilization could lead to additional reductions.
- Stormwater detention areas and other management practices can be reduced in storage volume and footprint area. Modeling results from the developing case study area indicate that stormwater management areas in areas without soil quality restoration would need to have 48%
Policies for Developed Areas
While many of the policies in urban areas are focused on new or redeveloping areas, it is important to look for opportunities to make improvements within the 43% of the watershed that is already developed. Cities can require updated stormwater practices to be installed on properties where site improvements or re-development is proposed to a level where a new site plan must be approved. Other than these situations, cities usually do not have the ability to force private property owners to make improvements to their sites. For this reason, communities may decide to provide incentives (such as cost share programs, grants, utility fee reductions) to promote installation of new stormwater practices. Cities may also look to identify critical areas where stormwater retrofits could lessen the potential for flash flooding or streambank erosion along small urban tributaries. Education and outreach efforts can also broaden use of practices such as rain barrels and raingardens in residential areas.
Policies for Rural Areas
Over the next decade, it is expected that most water quality improvements will rely on voluntary actions taken by individual farmers and landowners. To support and accelerate the implementation of this plan, a series of policies and action items has been identified.
New sources of financial support are needed to support water quality improvements in rural areas. Many practices known to be effective at reducing pollutant loads and/or runoff volumes, but several of these have costs associated with their installation or the lost potential for agricultural production. There are many economic factors which may make it more difficult for farmers and land owners to commit to investing in these practices. Low crop prices may leave little room above the “bottom line” to devote to water quality initiatives. With higher prices, there is incentive to maximize productive land, potentially reducing available for buffers and other practices. Federal, state and local resources can be used to bridge this gap and provide water quality and quantity benefits that are important to the entire watershed.
- Develop private and public partnerships to develop precision business planning for agricultural areas, targeting those areas which currently farmed on an annual basis, but are routinely not profitable to the producer. These lands could potentially be set aside for water quality practices such as conservation easements, wetlands, buffers, etc.
- Additional educational materials are needed that better explain the best management practices that are included in the nutrient reduction strategy: what they are, where they are best applied, how they work, their benefits and liabilities, and where interested groups can seek out more information for funding or constructing such practices. The need for such materials extends beyond the boundaries of this watershed.
- More information on existing research needs to be accessible to explain to producers and landowners what would be considered “natural” levels of nutrient loadings and how current agricultural practices have been shown to impact these levels.
- Develop a stream buffer policy for voluntary implementation of stream buffers and grass waterway improvements throughout the watershed. It would be recommended to provide a buffer of native vegetation, which protects areas expected to be inundated by a five-year flood event. Also, it is recommended that grass waterways or other buffers be provided along “zero order” streams so that they are protected for a width of one rod (16.5 feet) on either side of the stream.
- Practices that improve soil health and address water management have benefits beyond water quality and quantity improvements that should be pursued.