Agenda - Planning Commission - 07/12/2018

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Zoning for Coastal Flood Resilience By Joseph DeAngelis Flooding poses a considerable threat to the well-being of coastal cities and towns. Most coastal communities are well acquainted with the flood risks from the array of poten- tial tropical disturbances, less impactful but more frequent coastal storm events, and increasingly common nuisance flooding due to rainstorms and high and king tides. Impacts associated with sea -level rise have ceased to be a prospect and are now becom- ing a reality for municipalities on the coast. While the integration of hazards and climate resilience into comprehensive planning efforts has been a welcome devel- opment in recent years, local implementation processes are where coastal adaptation measures must take root. Where a hazard mitigation and emergency management plan may have sufficed in the past, the integration of coastal flood adaptation into the standard repertoire of local implementation tech- niques is vital to long term resilience. Zoning and land -use regulations are well suited to address long-term flood resilience by direct- ing both the general form and location of coastal development. This edition of Zoning Practice will sum- marize the spectrum of risk coastal flooding poses to cities, discuss zoning and land -use approaches that can help communities to adapt, and highlight relevant zoning reform efforts in Mandeville, Louisiana; Norfolk, Virginia; and New York City. HIGH AND DRY ON THE WATERFRONT — FIVE YEARS LATER zo17 was a landmark year for coastal storms. Three of the five costliest hurricanes in U.S. history all came in the space of a single, mer- cilessly active hurricane season. September 2017 alone was rated as the most powerful month for Atlantic coastal storms on record. Hurricanes Irma, Maria, and Harvey covered the spread of major hurricane impacts. Hur- ricane Irma's winds topped out at 185 mph, making it the most powerful Atlantic storm on record. Hurricane Maria brought devastat- ing wind, rain, and coastal flooding to Puerto Rico, where the death toll likely lingers in the range of 50o to 1,00o people, far in excess of the official toll of 64. Hurricane Harvey brought biblical rainfall to the sprawling Houston metropolitan area. In Nederland, Texas, Harvey dumped 60.58 inches of rain, the largest volume of rainfall attributable to a single storm in the lower 48. These storms, together with Hur- ricanes Katrina and Sandy, signal that the billion -dollar future isn't just more likely, but imminent. Taken with rising sea levels due to climate change, the risks to coastal cit- ies and towns are clear: Flooding is likely to increase in regularity and worsen in intensity in the near and medium -term future. White the role of the federal government is con- siderable, particularly in the context of the National Flood Insurance Program (NFIP), the Federal Emergency Management Agency's (FEMA) ubiquitous Flood Insurance Rate Maps, and the Natural Hazard Mitigation Grant Program, state and local governments must ensure that they are doing all they can to mitigate coastal flooding. Zoning is one of the major tools at the disposal of municipalities that are looking to reduce the exposure and vulnerability of its citizens and structures to coastal flooding. From tot -level design requirements and standards to overlay districts, rezonings, and map amendments, the zoning code and map are powerful ways of addressing flood resilience at a variety of scales. The November 2o13 issue of Zoning Practice, "High and Dry on the Waterfront" by Jim Schwab, FAICP, looked at the impact of FEMA's new Advisory Base Flood Elevation Maps for the City of New York, and the city's initial steps in addressing coastal flood adaptation through the zoning code. This issue also came on the one-year anniversary of Hurricane Sandy, an event that put New York City's vulnerability to extreme coastal flooding in stark relief. In this context, the city grappled with how the zoning code and the city's built environment actively conflicted with the basics of coastal flood adaptation. How do height limits in lower density parts of the city interfere with eleva- tion requirements in the wake of new FEMA flood maps? What about residential build- ings with accessory basement residences? How do you even begin to discuss the elevation of attached and multifamily build- ings? What happens to a commercial district when two dozen buildings with ground -floor retail uses require dry or wet floodproofing? As Schwab acknowledges in the article, while New York City is often considered an outlier around issues such as zoning codes and the built environment, the chal- lenges outlined above are not exclusive to New York. Given the direct flood impacts of Hurricanes Maria and Harvey on major met- ropolitan areas with diverse building stocks and wide ranges of density, the lessons learned in New York City post -Sandy have a surprisingly wide applicability. Later in this article I will dig deeper into the evolution of New York City's zoning and land -use strategy for coastal flood adaptation since "High and Dry on the Waterfront" and look at how the city's unique focus on both lot -scale inter- ventions and zoning map changes may be a model for other cities. COASTAL FLOOD RISK AND ZONING CONSIDERATIONS According to FEMA, 39 percent of the U.S. population lives in counties that are adjacent to open ocean, major estuaries, or one of the Great Lakes. A much smaller percentage live within FEMA's one percent annual chance (or ioo-year) floodplain. (A one percent annual chance (or ioo-year) flood means that there is an equal chance annually of major flood- ing, not that major flooding is only allowed to occur once every too years within a spe- cific geographically defined area.) FEMA's flood insurance rate maps follow historical precedent, and future flood events tend not to consider the lines drawn on regulatory maps. That maps follow the historic paths of floods and not vice -versa is a surprisingly common realization for both the public and practitioners, and one I encountered often as a community planner forthe East Shore of Staten Island after Hurricane Sandy. Of course, coastal inundation flooding is not solely the domain of tropical distur- bances. Nor'easters and similar offshore events can also cause storm surge and inundation of populated coastal areas. High tide and "king tide" (the annual highest tide ZONINGPRACTICE 6.i8 AMERICAN PLANNING ASSOCIATION I page 2