Preparing For Climate Change: A Small City’s Mid-century Culvert Drainage Needs

Presentation (pdf document)

Michael H. Simpson, Resource Management and Conservation Program, Environmental Studies Department, Antioch/New England Graduate School, Keene, NH, 603/283-2331, msimpson@antiochne.edu

Latham Stack, Syntectic International, Portland, Oregon, 503/901-1939, lstack@sytectic.com

Thomas Crosslin, Integral Consulting, Portland, Oregon, 503/284-5545, thomas.crosslin@mac.com

Sigurd Spearing, ECS, Brattleboro, VT 05301, 802/257-1195, sspearing@ecsconsult.com

Emily Hague, Monadnock Conservancy, Keene, NH, 603/357-0600, emily@monadnockconservancy.org

Numerous studies report that climate change induced precipitation intensification will stress civil infrastructures. Climate change preparation, generally called adaptation in the literature, has become a focus of many recent studies, accompanied by recognition of the need for specific projections at the local level.

Our study focused on the White Brook watershed in Keene, NH. Using the current Global Climate Change models (GCM), we projected the percentage of culverts to be under-sized due to an increased frequency of more intense precipitation amounts, which can be expected to manifest itself for this part of the Northeast. We then combined our statistical analysis of the GCM with a watershed build-out projection based on current City zoning. The study also estimated the associated cost to upgrade the projected failed culvert infrastructure. Finally, we sought to clarify the impact of advancements in statistical methods on future design storm estimates.

Results projected 48% of culverts in the study site are likely to be undersized at an upgrade cost of $226,000. Extrapolating this undersized rate to the City's 248 culverts yields a total upgrade cost of $2.5 million, in current dollars. With such projections, the City of Keene, and other such communities, may have a window of opportunity to prepare.

This study makes an important contribution to climate change preparation, by establishing the feasibility of specific estimates of civil infrastructure vulnerabilities, as planners and engineers consider preparing for predicted increases in rainfall intensity and watershed runoff.