452.b. Watershed Master Plan (WMP)

Possible Points: 315 points for the element.

Purpose of Element: According to the CRS Coordinator's Manual “the objective of watershed master planning is to provide the communities within a watershed with a tool they can use to make decisions that will reduce the increased flooding from development on a watershed-wide basis.” Successful watershed master plans:

1. Evaluate the watershed’s runoff response from design storms of various magnitudes and durations under current and predicted future conditions,
2. Assess the impacts of sea level rise and climate change,
3. Identify wetlands and other natural areas throughout the watershed,
4. Protect natural channels,
5. Implement regulatory standards for new development such that peak flows and volumes are sufficiently controlled,
6. Include specific mitigation recommendations that should be implemented in order to ensure that communities are resilient in the future, and
7. Have a dedicated funding source like a stormwater utility in place in order to implement the mitigation strategies recommended by the plan.

For more information on the CRS program’s requirements for watershed master planning reference pages 450-14 - 450-18 of the CRS Coordinator’s Manual.

Impact Adjustment: Yes. The impact adjustment for this element is calculated by taking the ratio of the area addressed by the watershed master plan to the area of the watersheds that drain to water bodies that pass through or are located in the community in question. This impact adjustment calculation must be accompanied by a watershed impact adjustment map that includes data from element 452.a. SMR as well as data from this element. In general, all watersheds that drain to a waterbody within or through community-limits are included on this watershed map. If a watershed exceeds 50 square miles in size at the point at which it enters the community's jurisdiction, then the community can choose to exclude the upstream portion of the watershed from their calculations of the total watershed area for the community. Areas of the watershed that will not be developed like state or federal parklands and preserves may also be excluded from calculations of the total watershed area. Special adjustments to the total watershed area can also be made if a flood control structure is impacting the contribution of upstream portions of the watershed, consult with your ISO/CRS Specialist to determine if this applies to your community.

Potential to Double Count Credit: None.

Degree of Difficulty - Documentation: Medium. There is a large amount of documentation that must be assembled in order to take credit for this element. In addition, the impact adjustment map communities must create requires a large amount of data and some GIS expertise.

Degree of Difficulty - Implementation: High. If parts of the watershed are outside the community’s jurisdiction coordination with the other communities is required. In addition, hydrologic modeling is required to determine the present and future runoff conditions. Not all communities will have an individual on staff that is capable of completing this kind of modeling, and as a result will need to hire a contractor. To earn credit for this CRS element, communities must adopt regulatory standards that, at the very least, are creditable under element 452.a. Stormwater Management Regulations, require that runoff from all storms up to and including the 25-year event be managed, and ensure that future peak flows do not increase over current rates. In addition, some coastal communities are required to evaluate the effects of sea level rise. The implementation of these regulatory standards could be met with opposition in some communities. As a result, the degree of difficulty associated with implementing this CRS element is high.

Tip for Success:

1. One strategy for reducing the effort associated with implementing this CRS element is working with neighboring communities that share watersheds. Working with other communities can help to maximize credits for the CRS element because of the way the impact adjustment is calculated. In addition, by working with neighboring communities, the cost associated with completing the hydrologic modeling necessary to earn credit for this element could be split.

Co-Benefits Associated with this Element: While creating a WMP may be difficult, the benefits are great. A WMP is more comprehensive than a stormwater runoff plan. Using watershed master plans can help communities to reduce the possibility of flooding within entire watershed. A WMP that bans shoreline hardening, requires the use of green infrastructure, and encourages the protection of floodplains or upland wetlands for stormwater conveyance or storage will also provide increased habitat for wildlife and improve water quality. Finally, the creation of a watershed master plan can help communities to plan for the predicted impacts of sea level rise. Thus, enhancing the resilience of the community in the long run.