Climate change isn’t the only factor causing changes in how water moves; it’s also our infrastructure choices. Traditional stormwater management (gray infrastructure) puts us in a fighting position against water, imprisoning its flows in pipes and drains. When we try to resist and restrict what water wants, it retaliates back. Forcefully. 

This past fall/September, Leominster, Massachusetts, was pummeled by torrential downpours. With 10 inches of rain falling in just 4 hours, life-threatening flash floods quickly became a frightening reality. Vulnerable residents had no choice but to watch as the merciless water charged into their businesses, schools, and homes, sparing no property in its path. 

Exposed pipes in Leominster, NBC

The hilly topography of Leominster exacerbated the issue, sending the water to flow across surfaces at lightning speed. Existing problems in one of their dams forced residents in low-lying areas to evacuate. Altogether, up to 300 individuals were evacuated—many by boat. Streets were sucked through sinkholes, most buildings were flooded, and several even collapsed. 

University of Louisville, Jared Hatfield

The University of Louisville in Kentucky faced a similar catastrophe in 2009 when 7 inches of rain fell in just over an hour, causing about $15 million in damage. The common denominator comes down to one factor—lots of gray and not enough green. 

University of Louisville, Jared Hatfield

Many cities lack green space, with impervious surfaces and gray infrastructure dominating instead. When cities lack soil, vegetation, and permeable surfaces, water has nowhere to infiltrate. It falls rapidly across the concrete, ending up in the nearest waterway or into drains that are becoming overwhelmed by the increased volume of water flowing in; in both scenarios, flooding is always possible and can cause severe damage, like in Leominster and Louisville. 

Rain Garden at the University of Louisville

The University of Louisville set an example to other communities by responding promptly with a variety of green infrastructure: rain barrels, vegetated roofs, rain gardens, and bioswales were implemented to facilitate groundwater recharge through infiltration. Impervious surfaces in lots, roadways, plazas, and sidewalks were replaced with pervious pavement, tree boxes, infiltration trenches, and paver strips, allowing water to access soil while avoiding existing utilities as well. The remaining hard surfaces and fast runoff areas were equipped with large underground infiltration basins to collect rainwater. With these improvements, the university diverts 72 million gallons of stormwater every year. 

50,000 gallon cistern at the University of Louisville

A crucial part of green infrastructure is the role soil plays in slowing water. If soil is weak or shallow, water infiltrates slowly, and the surface layers become saturated more quickly. When the soil can’t hold as much water, more runoffs occur. Deepening healthy soils would allow water to be absorbed and slowly released from the ground over time. From above to below ground, vegetation aids in decreasing runoff and sedimentation, all while helping to regulate the water cycle. Above ground, plant leaves intercept rainfall, stop water from hitting the ground at high speeds, and slow water flowing across the surface. Below ground, plant roots improve soil erosion resistance by holding soil particles together. Plants remove water from the soil through evapotranspiration, preventing it from becoming oversaturated by rainstorms. Overall, vegetation can reduce surface runoff by more than 50% and soil erosion by over 90%. 

The number and severity of extreme precipitation events will only increase alongside climate change. Water will only get faster. We must be proactive, stop working against water, and learn to work with it instead in the form of green infrastructure. Green infrastructure actively collaborates with nature, leveraging the capabilities of soil and vegetation to infiltrate, redistribute, and store stormwater volume, making communities safer and healthier.

Watch Out for Water! was written by Meriam Alessandroni, ORI Summer Intern.