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.