Blue Cities Restoring Natural Hydrology to Urban Environments
CRWA's Blue Cities incorporates the design of natural green corridors and infrastructure to help treat stormwater runoff before it enters the Charles and its tributaries – all while enhancing neighborhoods and connecting existing open spaces.
Restoring urban greenscapes and natural hydrologic function is at the heart of CRWA’s Blue Cities Initiative. Using historic maps as a starting point to understand how rainwater once functioned before urbanization, Blue Cities analysis evaluates opportunities for restoration that work with, rather than against, natural hydrology. CRWA evaluates soil types, historic groundwater flow, and historic versus constructed drainage patterns. This information forms the basis for retrofitting buildings, streets, and parking lots to capture and treat runoff, connect isolated greenspace, and create greenways—in effect, mimicking historic natural conditions. CRWA’s work includes partnering with others to build and monitor our demonstration projects, modeling the potential impacts of large scale Blue Cities designs, and training other environmental advocates, local residents, and municipal officials.
As in most cities, metropolitan Boston’s water cycle has been radically altered. Drinking water is piped in from 65 miles away, sewage is piped out to Deer Island Treatment Plant in Boston Harbor, streams are now buried, and pavement prevents rainwater from seeping into the ground. Developed areas are designed to collect and discard rain quickly, dumping runoff in rivers through storm drains. Massachusetts receives about 45 inches of precipitation every year; in the natural environment, almost half of this rainfall filters into the ground, and nearly all the rest returns to the sky as water vapor. In cities, we have paved over the ground and cut down many of the trees that turn water into vapor. The result: well over 50 percent of the rain in a typical year quickly becomes polluted stormwater runoff. Bigger storms overwhelm the system, resulting in flooding and, depending on the infrastructure, combined sewer and sanitary sewer overflows. The best way to reduce water problems in urban areas is to design cities so that they mimic the way nature handles water.
To make rain once again an asset that replenishes aquifers, and to reduce the pollution from stormwater and the risk of flooding from storm events, CRWA is working to reengineer urban landscapes to function more naturally. By designing natural green corridors and infrastructure that can soak up water and carry it slowly through the city, “Blue Cities” designs also enhance neighborhoods and connect existing open spaces.