"A drainage basin [or watershed] is an extent of land where water from rain or snow melt drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean."
(Source: Wikipedia (February 2009) - http://en.wikipedia.org/wiki/Drainage_basin)
With a historic water cycle, water in a watershed drained through the soil (also referred to as baseflow) and discharged along outwash areas into our wetlands, streams, and rivers, providing them with a constant supply of clear, cool water, year round, as shown in the image to the left below.
In the right image, you see a case where a watershed with a functioning historic water cycle is running into a watershed with a contemporary water cycle. The creek in the background flows through a typical suburban development where runoff is turned into a one-way waste stream. It is evident how those conventional stormwater systems overwhelm the creek and cause flooding.
The 168 Elm Ave. pilot project is located in the Salt Creek watershed. Like in the image above, the typical development and landscape treatment methods of my neighborhood push rainwater into a one-way waste stream, directly impacting Salt Creek (see also Runoff Quantity). I wanted to find out the magnitude of that impact and went to visit Salt Creek – and did not like what I saw.
The ecosystem along our waterways has no genetic memory of the frequent flooding caused by our contemporary water cycle and collapses under the stress of the constantly changing water levels and pollution. During dry stretches, Salt Creek is reduced to a trickle because we interrupted the baseflow (left image). As soon as it starts raining, water levels rise due to all the runoff we produce (right image).
And if it rains really hard, and our conventional stromwater systems reach capacity, we add insult to injury and force dirty and polluted runoff into the creek (see videos below).
Green and sustainable landscape treatment methods, such as at the 168 Elm Ave. pilot project, can offer significant relief to stormwater systems (see also Runoff Quantity). More importantly, they have the potential to eliminate runoff from smaller rain events. Let’s take a look at the two videos below, a heavy downpour (left) and a typical summer rain (right).
Heavy rainstorms such as in the left video are not that frequent. As such their damage is not that significant to the ecosystem in Salt Creek. The gentle summer rain to the right is our big problem. Right now, all those small rain events end up directly in Salt Creek and are cause for the unstable hydrology, poor water quality and the erosion and scouring along river banks.
Using green and sustainable landscape options can help to reduce or eliminate discharge from those small events and would help to rebuild baseflows; stabilize water levels and ground water (drinking water) supplies; reduce the risk of erosion, scouring and potential property damage; improve water quality; and have a restorative effect on our biodiversity and wildlife.
Green and sustainable landscape treatment options would allow us to reclaim waterways such as creeks as viable and healthy amenity or recreational spaces, which in turn can increase property values and our quality of life. And last but not least, the respectful and responsible treatment of water will contribute to the conservation of this critical, renewable but finite resource in your watershed.