Landscape Solutions for Storm water(Published in Today’s Home and Away)
The heavy rains that have pounded the city for the last week have affected all of us in one way or another. Many city residents have had to put up with unbearable hours in traffic while others have become accustomed to wading in murky waters as the storms turned city roads into rivulets.
Still others have had to put up with frequent power outages as Kenya power’s infrastructure gave in under the heavy downpour. And when it’s all done, The Kenya urban Roads Authority (KURA) will be repairing the city roads all over again.
But these are nothing compared to the lives and livelihoods that have literally been washed away as peoples’ homes and property are submerged or buried under rock and mud slides. Once again we are reminded just how vulnerable we are as far as managing storm water is concern.
Out of site Approach
While poor management of existing storm water infrastructure may be blamed for the perennial anguish that comes with the rains, the truth is, the way we have always dealt with rain water leaves a lot to be desired. The obsession with curbs, culverts and ditches that treat storm water as waste that need to be conveyed out of site as fast as possible is as tired as it is wasteful.
New approaches need to be sought urgently. Today there are new storm water management techniques that treat storm water as a resource that needs to be tapped at source and used to create amenities that enhance a site’s attractiveness and provide rich experiences for users. They address storm water management in environmentally responsible ways and create expressive landscapes that celebrate storm water. Here are some of them:
Detention and Retention
Storm water detention systems detain and store collected storm water runoff for a period of time, releasing it slowly to reduce flooding. Many times such systems are disguised as ornamental ponds in the landscape.
Retention systems on the other hand hold storm water for re-use in the dry season. Incidentally, such systems don’t have to be the traditional round or square galvanized iron or plastic tanks. They can be innovatively incorporated as landscape features such as fountains and waterfalls.
Filtration and Infiltration
Filtration systems do more than just retaining or detaining water on-site. They also reduce storm water pollution through various methods. Bio-retention gardens, for instance, use certain plants to systematically filter grey water into fresh water that can be used to water plants in the landscape and maintain ornamental water features.
Green roof systems and constructed wetlands consist of a series of manmade tanks or ponds that separates wastes and recycles water before allowing it to slowly filter into the ground. Both systems can be designed, not as hard mechanical systems, but as ornate landscape features.
Infiltration systems promote groundwater recharge. French drains are a good example of such a system. They redirect storm water into the ground and allow it to percolate slowly overtime. They include Infiltration trenches and basins as well as porous pavements.