Stormwater Management Effort

How many communities in the Piscataqua region watershed have adopted the Southeast Watershed Alliance Model Stormwater Standards for Coastal Communities and how many communities have other regulations in place? Additionally, how many communities in the watershed have a stormwater utility?

As of July 2017, in the 42 New Hampshire municipalities, 8 communities have adopted the complete set of stormwater standards; 7 communities are in the process of adoption; 5 communities have partial or a different set of standards, and 22 communities have not adopted standards. The 10 Maine communities are required to adhere to state-level stormwater management regulations. Zero communities have adopted a stormwater utility.


Stormwater runoff is a main driver of declining water quality in local waterways and leads to increased flooding. One way communities can reduce pollution and alleviate flooding is to adopt up-to-date stormwater management standards. This action will increase the resilience of each community and the region as a whole in the face of climate change and increasingly severe storm events and flooding.
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Adopting local stormwater management standards allows a community to grow in a resilient manner, while improving existing conditions and preventing future water quality impairments. In New Hampshire, state statute enables municipalities to adopt regulatory standards for stormwater management for projects not captured under state Alteration of Terrain regulations (projects smaller than 100,000 sq. ft. of terrain or 50,000 sq. ft. of protected shoreland).69 In Maine, the state Stormwater Management Law provides stormwater management standards for development that municipalities must adhere to (if projects exceed one acre of disturbance).

Communities in New Hampshire have already achieved many stormwater management successes through partnerships with the Southeast Watershed Alliance (SWA), the University of New Hampshire Stormwater Center (UNHSC), Soak Up the Rain, and other regional resources. Adopting enhanced standards allows communities to build on the great progress they have already made and continue to strengthen the culture of stormwater management leadership throughout the Piscataqua Region.

Local stormwater standards empower communities to guide development and protect natural resources while providing developers with consistent, equitable guidelines for managing impervious cover. These standards can be adopted in the zoning ordinance or as land development regulations. While any improvement to existing stormwater standards is a beneficial first step, the SWA model represents a comprehensive approach. Below is a summarized version of what is contained in the Southeast Watershed Alliance’s Model Stormwater Standards for Coastal Watershed Communities: Elements B-D.70 Stormwater experts encourage municipalities to include the following four components to minimize further water quality impairment and improve present conditions.

  • Threshold for Applicability: Creates a minimum threshold area of disturbance for new development projects that requires full compliance with stormwater standards.
  • Performance Measures: Improves water quality by requiring the removal of an established percentage of Total Suspended Solids, Total Nitrogen, and Total Phosphorous.
  • Groundwater Recharge: Promotes use of infiltration practices (groundwater recharge) to reduce runoff caused by a project and replenish groundwater supply.
  • Redevelopment Criteria: Requires improvements in stormwater management and treatment for redevelopment projects on existing properties. By capturing redevelopment projects this addresses existing stormwater runoff.

A 2015 UNHSC study of the Oyster River watershed found early adoption of enhanced stormwater standards could reduce average annual pollutant loads by up to 70% and save towns an estimated $14 million in avoided costs over the next 30 years.71 If other municipalities in the Piscataqua Region watershed adopt such regulations, future cost savings could increase dramatically. To track stormwater management progress across the watershed, PREP and its partners monitor which municipalities have adopted enhanced stormwater standards. Figure 22.1 reflects which communities have adopted the SWA model stormwater standards or something similar (8), which communities have adopted a partial set of the recommended regulations without redevelopment standards (5), and which communities have regulations pending (7). Overall, 30 out of 52 communities in the Piscataqua Region Watershed have adopted some level of stormwater standards, this includes the 10 Maine communities that adhere to Maine state standards.

In addition to adopting new regulations, communities are exploring creative options for funding sustainable stormwater management. One option is adoption of a stormwater utility designed to generate funding through user fees that are often based on a property’s collective amount of impervious cover within the utility district. A stormwater utility provides a stable revenue source to support long-term operation and implementation of a municipal stormwater program that addresses flooding, water quality, and aging infrastructure. These utilities require equitable cost distributions (charging owners with the most impervious cover their fair share), incentivize reduction of stormwater volumes through lower fees, and help communities comply with federal regulations. Many communities in Maine, Vermont, and Massachusetts have successfully adopted stormwater utilities. While no such utilities currently exist in New Hampshire (Figure 22.1), the cities of Dover and Portsmouth have conducted feasibility studies.72, 73

For more information:
Model Standards:
https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/Final_SWA_SWStandards_Dec_20121_0.pdf
Durham Study Fact Sheet:
https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/FactSheet%20-%20P2%20ModelingRV_WEB.pdf
Stormwater Manual:
https://www.des.nh.gov/organization/divisions/water/stormwater/manual.htm

Table 22.1 Number of watershed communities that have adopted a stormwater utility.

Figure 22.1 Map depicting adoption status of SWA model stormwater standards across 42 New Hampshire communities and 10 Maine communities.