Agenda - Planning Commission - 03/02/2017

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how to incorporate elements such as street trees, stormwater planters, and rain gardens (Boston 2013). Retaining Stormwater On -Site Local governments can require new develop- ment to retain all stormwater on -site through a site plan requirement. Developments could meet the requirement through green infra- structure elements and reducing the overall percentage of impervious surface. A stormwa- ter runoff credit -trading program would allow new development projects to purchase credits for off -site mitigation. In Washington, D.C., property owners who install green infrastructure can sell Storm - water Retention Credits to large development sites, which can use the credits to meet up to half of their regulatory stormwater reduction requirements. The city also buys some credits, as paying private property owners to install green infrastructure is more cost-effective than if the city government built the green infra- structure itself (Washington, D.C. 2016). Design Guidelines for Elevating Buildings A well -established strategy for buildings in floodplains is to elevate the structure. In highly developed places, removing all devel- opment is not an option, and elevation might be the only way to protect people and property from floods. However, elevation is expensive, and it can create a false sense of security. People with limited mobility might have trouble getting into elevated buildings. Design guidelines or form -based standards that pro- mote accessibility and a lively street can help mitigate some of the problems. After Superstorm Sandy, New York City updated its zoning code to make new construction and retrofitted buildings more resilient to floods. The city planning depart- ment worked with the architecture and design community to develop principles for designing elevated, flood -resilient buildings (NYC Plan- ning zo13). In 2013, the New York City Council adopted a flood resilience amendment to the zoning code that incorporated these design principles (New York zo13). The principles are: • Visual connectivity: Maintaining architec- tural elements such as doors, porches, stoops, and windows along the street ® Facade articulation: Ensuring that elevated buildings have interesting elements along the street instead of a blank wall ® Inviting access: Making sure that people with limited mobility can easily get in and out of the building ® Neighborhood character: Integrating ele- ments of the existing neighborhood design when rebuilding or building new construc- tion (NYC Planning zoi3) SEA -LEVEL RISE AND STORM SURGE Taking sea -level rise projections into account can help planners determine where develop- ment and infrastructure might be at risk now and in the future. Knowing where the shore- line is likely to change can help local govern- ments tailor development standards. Com- munities with working waterfronts can use zoning and other strategies to protect these economic and cultural assets. Updating Flood Zone Hazard Maps Local governments can add projected sea - level rise to flood zone hazard maps, currently based exclusively on historical events, to better plan for future conditions. This action would not affect flood insurance require- ments, which would continue to use Federal Emergency Management Agency -created flood zone hazard maps. The extended coastal flood hazard zone would delineate potential inundation areas, critical emergency facilities, evacuation routes, road elevation projects, and culvert replacements. It's recommended to use minimum 50-year planning horizon that assumes a plausible range of sea -level rise projections and takes into account land sub- sidence and uplift a and local conditions. The Rockingham Planning Commission is working with several communities on the New Hampshire coast to help them assess and pre- pare for the impacts of sea -level rise. For the town of Seabrook, the commission's vulnera- bility assessment included a recommendation to create a flood hazard overlay district that in- cludes the areas projected to be at higher risk in the future in addition to the areas mapped by FEMA's Flood Insurance Rate Maps. This district would include performance -based standards to protect against flooding. The as- sessment also recommends using this overlay map to educate property owners about risks from sea -level rise and storm surge (Rocking- ham Planning Commission 2015). Context -Sensitive Designations Context -sensitive shoreline classifications can set appropriate development standards for different settings. King County, Washington, updated its Shoreline Master Program land - use policies to include eight new classifica- tions that fit the varied shoreline. Regulations for the classifications range from very low -im- pact development for sensitive lands to flood prevention measures in areas where higher levels of development are appropriate. These classifications are incorporated into the coun- ty's comprehensive plan (King County 2016). These context -sensitive levels of development protect the most sensitive areas while still al- lowing development where it makes sense. Working Waterfronts Working waterfronts are often vital parts of a coastal community's identity and economy, and sea -level rise can threaten their viability. Recognizing and supporting these working waterfronts protects a sense of place and community history, and clusters similar indus- tries together, which can spur innovation and collaboration. However, communities should be careful of concentrating noisy, polluting industries in low-income neighborhoods. Also, consider resilience provisions that protect active working waterfronts from pol- lution releases in a storm surge or temporary inundation. Measures might include elevated material storage or redundant flood protection measures to avoid exposing nearby popula- tions or ecosystems to pollution releases. Portland, Maine, has a historic working waterfront but found it challenged by aging infrastructure and the threat of sea -level rise. The city needed to find funding to keep in- frastructure in good repair and prepare it for the rising sea. An overlay zone, adopted in 2010, allows compatible non -marine uses to locate on the working waterfront. The city also encourages incremental improvements where possible to prepare for sea -level rise (National Working Waterfront Network 2015). EXTREME HEAT Communities can help protect their residents from extreme heat by identifying and improv- ing the hottest parts of neighborhoods, help- ing particularly vulnerable people stay cool in a heat wave, and encouraging new develop- ment to use materials that cool hard surfaces. Mapping and Remedying Hot Spots Extreme heat is exacerbated in built-up areas by the heat island effect. Buildings, roofs, and pavements absorb the sun's heat and create ZONINGPRACTICE 2.17 AMERICAN PLANNING ASSOCIATION I page 4