Sponge Cities

Sourced from Watershed Sentinel

The Department of Fisheries and Oceans slapped a ban on both personal and commercial shellfish harvesting throughout Baynes Sound recently because of heavy rainfall, which came “after a prolonged dry spell,” so would “adversely affect marine water quality.”

It’s a regular notice the DFO issues around most urbanized regions of Vancouver Island in the fall, and it usually lasts for more than a few days.

Why? Because every time it rains after a dry period, it’s as if a giant toilet flushes animal feces, fertilizers, pesticides, oils, road salts, heavy metals and other contaminants into municipal stormwater systems, which in turn send torrents of polluted water directly into watersheds, killing fish, eroding property and making waters unsafe for shellfish harvesting.

This is not a new problem. For the past 100 years, urban development has replaced natural vegetated land with impervious surfaces like roads and parking lots. This has diminished the amount of rainwater absorbed into the ground and reduced the dispersal of precipitation back into the atmosphere from trees (which do the heavy lifting) and other plants, via a process called evapotranspiration.

As a result, surface runoff has become the primary means of rainwater drainage.

To control flooding, Vancouver Island municipalities, like other local governments around the world, invested millions of dollars over time in underground infrastructure to channel rainwater runoff into rivers or streams. This not only polluted these waterways and killed wildlife, but the increased volume and speed of the moving water caused erosion and other flooding risks by altering the natural hydrologic cycle.

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