How Can We Reduce Flooding?

Since we had the recent cold front slowly move through the east and cause major flooding from Florida to New Jersey; I wanted to discuss some things regarding our infrastructure and how we're working against nature and not with it.  So much damage occurs from flooding: roadways get washed away, cars get flooded, houses are lost and major erosion happens.  If you consider how the environment has the ability to absorb water, it's amazing we don't work work with it more.  We have built a network of impervious surfaces, such as roads and parking lots.  These impervious surfaces increase the amount of water suspended on the land surface, causing flooding to occur.  We altered the landscape to allow for a more comfortable drive and aesthetically pleasing look.  In doing so, we completely degraded the environments ability to absorb water through the soil.  This not only leads to flooding, but a host of other nasty side affects, such as: higher temperatures and increased pollutants to our rivers, streams and lakes.  However, what can we do to combat this issue?

Under natural conditions, only about 10% of precipitation runs off the surface of the landscape, 50% soaks into the ground, and a surprising 40% is taken up by the trees and other vegetation and sent back into the atmosphere through the process of evapotranspiration (P. Flinker, 2010).  This is simply astonishing!  So I shouldn't even say it but I will, cutting vegetation + impervious surfaces = bad news bears.  If the precipitation is not able to penetrate the ground surface it becomes runoff and is dumped into small streams and creeks.  Approximately 75% of the stream miles that feed our waterbodies with clean water are small enough to be straddled by a child (P. Flinker, 2010).  This makes these streams very sensitive to land use changes and susceptible to pollution.  We must understand this and put management plans in place to control this unnatural flow of water.  By keeping overall impervious cover below 10% of the landscape, the landscape will retain its natural ability to absorb runoff and filter runoff from developed areas and prevent flooding (P. Flinker, 2010).

Figure 1-Changes in site hydrology with increasing impervious cover (US EPA)

Filtration of the runoff through the soil is imperative to clean water.  The environment has a natural "Brita" water filter built into it, it's called soil!  Soil filters impurities and makes clean water which is filtered into our aquifers, streams, rivers and oceans.  After all, this is where our drinking water comes from!  It's amazing we care more about materialistic things in this world and not this!  We will have to save that rant for another blog in the future.  If you haven't got the trend here, EVERYTHING is interconnected.  How we interact with our surrounding DOES affect us.  Without the filtration of the runoff an increase of nitrogen and phosphorus enters our water system.  This leads to dead zones in our bays and waterways and red tides in our oceans, caused from algae blooms (L. Polycarpou, 2010).

Figure 2-Showing a red tide (M. Godfrey)

I did not want this to turn into a research paper by any means, I just want to portray how interconnected we are with our environment and how we are doing things a** backwards!  So here is the big question, what can we do to decrease impervious surfaces and increase water absorption?  

1) Green Roofs

Research has shown that green roofs retain over 50% of precipitation (EPA).  This is beneficial, less roof runoff=less water in the streets.  Green roofs seem like a no brainer compared to an artificial asphalt roof that retains 0% of runoff.

Figure 3- Green roof (B. Victoria)

2) Rain Gardens

Rain gardens allow for runoff to be absorbed and filtered back into the ecosystem. These can be placed around homes, roads, overpasses and parking lots to improve physical and biological integrity.

3) Permeable Surfaces

This allows water to penetrate the surface which decrease surface water flow and runoff.  Think if we made all parking lots, driveways and sidewalks of a permeable surface!  That alone would decrease flooding from surface water runoff. 

Figure 4-Permeable surface (Expocrete)

These are main examples of what we can do to improve water quality and decrease flooding.  The next time a heavy rain passes through, remember this blog and observe how much surface water is retained from impermeable surfaces.  Nature is a spectacular marvel!  It blows my mind to think that we have been given the tools to live in a less polluted and degraded world, but we destroy those tools with our own man-made version?  How does this make any sense!?  Hope you enjoyed my rant on how we can reduce flooding.  Please share if you enjoyed or learned something.  If you want to add anything, by all means comment.