As homeowners we impact our waterways, sometimes with disastrous effects.  More development means more impermeable surfaces.  Impermeable surfaces are hard surfaces that do not allow water to pass through them.

Our rooftops, driveways, and even our lawns keep water from seeping into the ground.  When water can’t infiltrate, it runs off the site.  A typical city block generates more than 5 times as much runoff as a woodland area of the same size.  

This runoff then enters concrete storm sewers that direct the water into streams, lakes, rivers and wetlands.  Runoff gains speed inside smooth sewer pipes, and when the water finds the end of the pipe, the pipe, the power of that rushing water damages vegetation, exposes eroded bank sides, and destroys aquatic habitat.

And the water coming out of that pipe carries a lot of bad stuff into our waterways.  Rain washes our hard surfaces, picking up automotive fluid leaks, toxic chemicals, heavy metals, salts, and sediment along the way. Our lawns often hold pesticides, herbicides, fertilizers and pet waste, all just waiting for the next rainfall to wash their viruses, bacteria, chemicals and nutrients downstream. 

Pavement and roofs heated in the sun make runoff warmer.  It may be hard to imaging the impact of warmer water, but try standing barefoot on a sun-warmed driveway and then running a cold garden hose on your toes.  This is similar to the shock that aquatic life experiences when warm water enters a cool stream. The napkins in my elementary school used to say, “You Are What You Eat.”  In the same way, our waterways are becoming what falls into them. 

You can reduce your impact on your local waterways by reducing runoff volume, lowering runoff temperatures, or removing pollutants.  Here are some manageable ways you can make a difference: 

1)     Rain gardensYou can install a rain garden that will capture the first inch of rainfall - “first flush” that carries the most pollutants.  Or you can install a rain garden that holds a 2” rain event, which would be almost any storm we get around here.  One apartment owner in Minneapolis installed a rain garden to handle nearly six inches of rain – we only expect to get a storm like that once every 100 years. 

2)     Permeable surfaces     Patios, paths, driveways (or portions within the driveway) can be replaced with permeable surfaces that allow the water to pass through, entering the underlying subsoils.      

Types: 

a) Grid structures generally made of recycled plastic are filled with granite or sod. 

b) Permeable pavers allow water to pass between stones into base layers of granite aggregate.

c) Porous asphalt and concrete allow water to flow right through them into granite aggregate below. 

3)     Infiltration trenches     On top these structures just look like rock, but underneath they store rain water and allow it to infiltrate to subsoils. 

4)     Filtration plantings      Native plant materials are extremely effective in filtering pollutants, sediments and lowering water temperatures.