Flooded Sidewalks, Flooded Cities. Is There a Way Out?

Have you ever successfully navigated a puddle-filled sidewalk only to look up and see the impenetrable lake ahead? You should have known there was no hope. Here's looking to the future.
In September, the Illinois EPA announced its implementation of measures to reduce storm water runoff. It's called the Green Infrastructure Grant program, which has $5 million dollars from the US EPA already in its pocket.

There are a large number of technologies supported by the new program. But, ever since I was introduced to  permeable pavement (PP) technology at the EPA P3 (people planet prosperity) Expo last spring, it has been my favorite. They are exactly what they sound like. Unlike typical pavements, these allow water to seep through and into the ground below.

IL EPA and local officials showcasing semi-permeable block pavement (Sept. 16th, 2010)

Types (detailed information):

• Block Pavers (pictured): These are impermeable (often concrete) blocks that are interlocked/spaced in a way that allows water to penetrate the soil below. Some brands include Aquaterra, UNI Eco-Stone, SF-RIMA, Turfstone, and Hastings Checkerblock. 
• Grid Pavers: These are the weak cousins of block pavers. They are typically made of plastic and can be filled with grass, gravel, or soil. Examples include Turfgard, Netpave, Gravelpave, Grasspave, Tufftrack, and Geoblock.
• Permeable Asphalt/Concrete: These are the originals without finer particles in the mix. The absence of these particles leaves voids through which water can flow. Check out the design below. 

Permeable asphalt design

Here are some pros and cons of permeable pavement. Keep in mind, all designs have different capabilities.

PROS:

• limit flooding
• reduce chemical runoff, which harms lakes/rivers/streams
• allows water to seep back into the water table, replenishing aquifers

Before and 10 years after permeable pavement installation at Brown University (2004)

CONS:

• may be vulnerable to ice damage, called frost heave, in freezing temperatures. However, there have been pavements designed to resist it.
• can't handle heavy loads (like trucks) or large amounts of traffic (busy roads).
• may require a little maintenance. Some types of permeable pavement are prone to get small rocks stuck in the pores. Occasionally, these may need to be cleaned via street sweeping or vacuuming.
• cost more.

Because of current performance specs, permeable pavement is limited to areas like sidewalks, walking paths, bike trails, parking lots, low traffic side roads, driveways, etc. Hopefully, in the future, design breakthroughs will allow permeable pavements to be used more widely in the world. Perhaps one day, they will answer to urban flooding like that in India. 

Chicago is Safe, but for How Long?

Various nations in Africa and South America have begun to recognize that collaborative efforts may be necessary in order to control freshwater exploitation. This is apparent in the recent call for aquifer use agreements, which would protect cross-country water resources.

Various aquifers in question

In order to protect our water resources, it is important to understand how we are affecting them.
What are we doing wrong? (from what I gather is least to greatest impact, please share your ideas)

1. Road Salt: I always wondered how it could possibly be environmental OK to use so much road salt. I asked myself, "how can there be no consequences when 2 minutes of driving encrusts my car in it?" Apparently, it does matter. One study published this year shows that runoff from salted roads increases water salinity in rivers/streams/lakes, threatening plant and animal life.

Snow or salt?

2. Unleashing Aquifers: Our aquifers are being  drained faster than they can naturally be recharged, causing water shortages in places from Wisconsin to India. That's not the only problem. The water we release from the ground eventually ends up in the world's oceans and is responsible for 25% (.8mm/yr) of rising sea levels.

3. Global Warming: There is significant evidence that global warming hastens the water cycle, which results in increased evaporation and precipitation. Unfortunately, when you mess with the water cycle, you don't get more rain everywhere. In wet regions, rainfall increases, which fosters damaging floods. In dry regions, less rain will fall, and freshwater bodies may increase in salinity and/or dry up, which may cause devastating droughts.

I've always had great appreciation for Chicago. It isn't just because of the city's impressive architecture, positive energy, and seasonal variation. It's also because when the world's water supply fades, Chicago will be at the heart of the largest freshwater system on Earth, The Great Lakes. However, my guess is that, in time, even Chicago won't be immune.



Evidence from near and far:

• East Antarctic Lakes have seen increases in salinity.
• Salinity increases in India have led crocodiles into populated areas.
• Cities in Wisconsin were hurting when they were cut off from Lake Michigan.