Once upon a time, the rain fell in lovely droves. It freely splattered and gushed and rushed and rolled. And then all that energetic water promptly drained into the earth, absorbed by the roots of plants and trees, and naturally filtered through soil and rocks before getting stored underground.
From one state to another: water’s movement in our planet (Image from Culligan.com)
That’s basically the gist of groundwater recharge. It’s a nice-sounding name; “recharge” almost seems like a dynamic process, as if water was being refreshed and transformed and made new again. We’ve all been taught the wondrous water cycle in our grade school years—how water from our rivers, lakes and seas evaporates and becomes clouds, and then condenses as rain or snow, falls back to earth, joins the rivers and lakes and seas again, and some of it seeping into the ground.
So yes, in many ways, it really is a dynamic, even magical process. Everything is taken care of naturally.
And Then the World Was Paved
Sadly, all that dynamic and magical process gets disrupted in our built world.
Paved in concrete and asphalt, the ground is effectively barred from absorbing and filtering stormwater. Water now has no choice but to rush aboveground, carrying with it man-made pollutants and contaminants such as grease and oil, road salts, heavy metal, pesticide and fertilizers residues, sediments, and many others. All these empty into drains and sewers and end up into lakes and rivers, endangering aquatic life.
Toxic algae which feeds on excess nitrogen and phosphorous pollution is of concern too—their unchecked growth kills fish as it destroys the natural balance of lakes and rivers.
Paved surfaces promotes flash flooding as well. The onslaught of water erodes riverbanks, deposits sediments into the water, and even compromises the structural integrity of bridges. Aside from environmental problems, stormwater poses monetary costs as well—needed for infrastructure repairs, purifying our drinking water, river dredging, etc.
Stormwater Management Techniques
It’s easy to see then that with poor stormwater management everybody loses, and that’s why it’s everyone’s concern, and not just the job for engineers, builders, and urban planners.
(Image from tmdl.bse.vt.edu)
Fortunately, solving the issue of stormwater runoff isn’t all that hard. Actually, a lot of it has to do with going back to basics—the way nature has been doing it all these time.
The EPA has a great list of Stormwater Management best practices. It’s an engaging read, made more relevant especially considering the shifting patterns of rain and wind made abnormal now by climate change.
Some are beautifully low-tech and low-impact solutions while some involve a bit of planning and construction.
Rain gardens have the dual purpose of absorbing stormwater and beautifying the surroundings.
Rain Gardens. Also called bioretention cells, a fancy name for of a shallow depression in the ground with porous backfill, where stormwater can be directed to pool and naturally drain. Sturdy native plants that can resist drought and overwatering are planted all around, their root system assisting in the absorption of the water.
Green Roofs. Roof spaces with load-bearing capabilities are utilized as mini gardens where drought-resistant and flood-tolerant plants can grow—consequently helping to reduce stormwater runoff, absorb the city’s CO2, yield vegetables and herbs, as well as beautify the surroundings.
Curbless and Gutterless Street Design. Curbs and gutters only serve to channel and hasten the surge of stormwater into a drain, without giving water the chance to get filter by the ground. Curbless and gutterless street design lets stormwater take the form of a sheetflow—wherein water is uniformly dispersed into a flowing sheet instead of an overwhelming gush of water.
Swales. Just like rain gardens, grass-covered swales act as natural drainage system for stormwater, slowing runoff while efficiently filtering it too. Natural low-lying areas should be preserved and utilized for their stormwater management capabilities.
Permeable Pavers. Interlocking paving blocks let stormwater seep through the edges and into the soil. The grass that grows in between the pavers help with the absorption through their roots.
Porous Pavement. Instead of impervious concrete or asphalt covering the ground, say a parking lot or driveway, permeable pavement is porous so that stormwater can seep through into a stone reservoir underneath.
Tree box filters: pretty and purposeful.
(Image from PhillyWatersheds.org)
Tree Box Filters. Here, a box planter for a tree is installed underground, for water to drain into the soil and be detained for a while before being released into a catch basin.
Rain Barrels & Cisterns. It seems foolish to let all that falling rain go to waste considering that in water-deprived regions in South Africa, villagers painstakingly harvest water through fogs that condense in strategically-placed nets just to have water for daily use. Rainwater collected in barrels and cisterns can be used for watering lawns and gardens, flushing toilets, etc.
Putting It All Together
Other best practices for stormwater management include soil amendments (to improve soil’s ability to absorb and filter), riparian buffers, sand & organic filters, infiltration trenches (rock-filled ditches), water quality inlets (meant to separate sediments and free oil from stormwater), inlet protection devices, and many others.
Every project site calls for a unique stormwater management technique (or a combination thereof) because of many inherent factors, such as
- Landscape’s natural feature
- Presence (or absence) of slopes
- Natural flow path of water
- Soil type
- Nearby bodies of water
- Hydrology in the area
- Preexisting developed area
There was a time when stormwater management was all about simply channeling the water away from the site as quickly as possible to prevent flooding. It did the building a lot of good, but posed problems elsewhere. Today managing stormwater means utilizing the natural features of the land, and building the appropriate mechanisms. The techniques mentioned above, once put together, help restore that fragile balance of the process of water cycle.
One more building that gets erected with no concern for stormwater runoff poses yet another sad disruption to our water cycle. We need buildings and cities that harmonizes well with nature, not surly, impervious structures that blatantly ignore their relationship with the environment. Given the unpredictable weather patterns nowadays, we need them more than ever.
