Track 2: Sustainability and Conservation of Built Heritage in the Americas
As preservationists, we are connected to our past through the stories behind the places we strive to protect, and one of the most common stories ingrained in the fabric of nearly every historic site is: The Flood. Floods exist in myths and legends, but they are also real, tangible events tied to places and times, embedded in our memories as specific dates (The Flood of 1936), names of storms (Hurricane Sandy or Katrina), or locally recounted simply as: “The Great Flood.” We must engage with this history when we consider the impact of future floods, and use the knowledge gained from past events to assist with making decisions on how to preserve historic sites.
Unfortunately, there is a new twist to the past flood narrative. Floods are increasing in severity and frequency, causing destruction at unprecedented rates and forcing local jurisdictions and professionals to play catch-up. Recent flood events in Ellicott City, MD demonstrate the changing trend in devastating fashion. On 30 July 2016, flood waters reaching above 8-feet deep and travelling over 10-feet per second plunged down Main Street. Emergency stabilization saved many of the historic structures only to be hit by another equally devastating flood less than two years later. This town has a history of flooding from the river, but these recent events originated at the opposite end of town as flash floods due to runoff. The frequency, severity, and character of the recent floods have left many to wonder, why is this happening, and what, if anything, can we do to protect our historic cities against future events?
We understand that over-development upstream leads to increasing flood risks downstream and impacts many historic city centers. This presentation will describe methods to quantify the increase flood risks caused by man-made changes to local watersheds and climate change. Quantifying the negative impact of development will help lead to collective action to reduce the risks from flood events.
Cities have begun to change their regulations to require on site water retention. Slowing the rate of runoff reduces the frequency of flood events and allows existing storm water management systems to operate without significant and costly intervention. Unfortunately, these laws have created unintended consequences; many historic properties are not exempt.
Finally, we will tie the knowledge gained from hydrologic and hydraulic studies together with new design requirements from recent city regulations to compare the effectiveness of different strategies to protect our historic fabric. We will consider strategies implemented at a project and local levels to combat the increased risks of floods to develop a framework for future projects, planners, and owners to reference as we all continue to wrestle with this problem.