Hurricane Irene, who was down graded to a Tropical Storm, embraced Vermont on Sunday the 28th of August. The rain swelled the rivers over their banks; flooding downtowns, stranding many with road closures, destroying bridges, disintegrating mountain roads and taking down power lines leaving many without power. The 100 year flood plain is something that isn't documented well enough nor heeded when it is.
In Permaculture, observation is your number one "tool" and water is a key element to watch throughout the season and especially in instances like the flooding of Irene. In a sustainable whole system design, documented observations of waters movement through and over the land are invaluable.
We have issues in Vermont, with our many mountain rivers and streams that have very large river basins in comparison to their embankments. There are solutions to these issues, especially in our towns and cities, but these solution are extra investment. The short term prospectors could actually see this type of destruction as being beneficial, by having to rebuild roads and power grid etc. you boost the economy with federal funds and work. This is one of the grand issues of our times, Shortsightedness used as a tool for the Capitalist model of indefinite growth. Meaning it is more valuable to the capitalist market to make things that don't last.
One of the largest design issues with flooding in populated areas is impermeable surfaces, namely asphalt. By not allowing water to penetrate into the soils it is collected and funneled from all these surfaces directly into the waterways, causing flash floods in the case of torrential rains. There are alternative materials like permeable asphalts but there are also innumerable ways the water can be diverted to areas where it will be used by "earth works" allowing it to peculate through the soils SLOWLY making its way to the streams and tributaries. One such system is called a Rain Garden, these can be installed in the middle of parking lots, the slope of the parking lot is such that it carries the water into the rain garden, instaed of heading right into the storm drains and culverts then directly into the waterways. There are many methods of "Dynamic Water Harvesting" which are the methods we need to implement.
Designing Rain Gardens PDF
In theory, approximately 0.62 gallons can be collect per square foot of surface area to every inch of rainfall. Lets take a 10x10 surface of asphalt in the case of Irene's 11inch of rain, it collected 682 Gallons. This gives you an idea of how much water we are diverting directly into the waterways.
For more information - rain water harvesting manual PDF
Why is this such an important factor in designing our cities and towns? A number of reasons, human safety, saving costs on repairs and environmental damage through pollution are just a few. Our sewage treatment systems and storm water systems are a large issue in this design flaw where flooding is concerned. I am not an engineer and don't claim I have all the solutions, what I am saying, is there is a need for Foresight in our design process through observation and implementation of proven methodologies.
This is an important part of being sustainable. If we require millions of dollars in Federal aid every time a 100 year flood happens (which could become every year), we are far from sustainable. I see this investment in town designing for longterm resiliency to weather just as important as renewable energy production in this age of climate shift. Mapping the flood zones, river basins, and town rain water surface collection and its course through the watershed is the first step. Now is a great time to gather this invaluable information, so we can put it to use in our future designs. If we just rebuild and repair everything returning it to the way it was, this level of damage will ultimately happen again.
Here is a video that describes the issue and some of solutions.