Microclimate, Heat Mitigation & Waterfronts

According to the 2023 USDA Hardiness Zone map, all of New York City falls within Zone 7B. NYC’s climate, now classified as humid subtropical, is changing rapidly. While large-scale design changes may not yet be feasible, the need for monitoring and adaptation is clear. Refer to the NYC Climate Resiliency Design Guidelines. Additionally, the site-specific environmental conditions such as sun exposure, wind patterns, and precipitation will ultimately create a unique growing environment for plants. This microclimate must be understood in order to select the most appropriate plants.

Recent trends of more extreme temperature and weather due to climate change will also impact plant selection. These trends will have a varied effect depending on the particular microclimate. For example, coastal and low-lying areas have experienced intensified and more frequent flooding due to more frequent storms over the last several years, which may require hardier drought and flood tolerant plants be specified. Additional considerations include:

Sea Level Rise: Rising sea levels will increase the extent, frequency, and severity of flooding, impacting both current and future landscapes. Areas not currently subject to saltwater flooding can be expected to become so, and areas currently flooding will be affected more severely. Existing wetlands may become partially submerged, and areas currently above and beyond the intertidal boundary may transition to tidal wetlands.

Rising Temperatures: Higher temperatures will alter the suitability of native plants, planting seasons, bud and bloom times, pest resistance, and growth cycles.

Rainfall Patterns: Intense rainfall events paired with drought conditions will require plantings resilient to both extremes. New York City Panel on Climate Change (NPCC) projections show a likelihood of increased incidence of intense rainfall with decreased “regular” rainfall. The combination of less snowfall and snowmelt and droughts with higher future temperatures also has implications.

Landscaping, particularly tree planting, is a critical tool in mitigating urban heat. Given NYC’s hotter climate and the NPCC projections of continued warming, the role of landscaping in heat mitigation is increasingly critical.

Roadways located near waterfronts, within coastal storm floodplains, or in tidal inundation areas differ significantly from otherwise identical inland roadways. These unique settings are influenced by water above and below ground, requiring tailored considerations from both a horticultural and landscape design perspective. On-going Resiliency efforts may also impact plant selection and use, such as providing opportunities for understory plantings to stabilize slopes or limiting the use of trees near Flood Protection Systems. Additional factors to consider include:

Coastal Storm Floodplains: These areas face infrequent but severe saltwater inundation during large coastal storms. Plant selection, tree guards, and other materials should account for this.

Tidal Inundation Areas: Streets subject to occasional extreme tide-related flooding need specialized assessments to address recurring saltwater exposure.

Saline Groundwater: Soils and plant roots are likely to be exposed to saline groundwater earlier than they are exposed to saltwater from tidal or storm overland flow.

Waterfront Streets and Street Ends: Waterfront streets are distinctive environments not only due to flood risks but also because of their unique public interaction. Design considerations should include viewsheds, airflow, edge treatments, and the overall user experience. Consider using a sunken planting area in place of a barrier to deter errant vehicles. Proactive planning for these areas, such as through the ongoing DOT Resilient Street Ends Study, is essential. Additionally, consult DCP for Waterfront Public Access requirements for adjacent parcels and to allow for coordination with existing or future public access areas and continuous access along the shoreline where appropriate.