Don’t wait for Melamchi, Tyle McMahon
Going with the flow, Liew Yu Wei
They have found that the costs of transforming drainage systems and building green infrastructure has significant benefits. Green infrastructure is a set of practices that utilise and revitalise ecosystems within and between watersheds, urban areas, neighbourhoods and households. Permeable pavement, rain gardens, bioswales, and household-level rainwater harvesting are common examples of green infrastructure solutions for stormwater.
As cities elsewhere have found, green infrastructure saves. Financially, green infrastructure reduces the capital investment and operational costs of urban infrastructure. For cities like Philadelphia in the US, the cost of implementation has been four times lower than conventional stormwater drainage and wastewater treatment system upgrades. New York will see significant savings over the lifespan of its project, both in capital and operational costs.
A review of over 400 green infrastructure initiatives by the American Society of Landscape Architects showed that three-quarters of these investments were as cost-effective, or more so, than alternatives. Moreover, these examples were primarily on-site initiatives and not at the city-scale, which can be more cost-effective.
Not enough for everyone, Sonia Awale
Nepal villages cope with climate-induced floods, Sonia Awale
In Kathmandu, 150 billion litres of rain fall on rooftops and paved surfaces in one year. Spread over 365 days this would be 420 million litres daily, but during the monsoon rainfall is much more concentrated. A 50mm storm produces 5.5 billion litres of stormwater, more than 50 times what wastewater treatment systems could handle if they were completely functional. The same storm would produce 5,000l of water on a normal household rooftop, 15 times their daily wastewater production.
If much of this water was retained and recharged on-site the cost reductions, additional groundwater supply available, and the reduced pollution of the Bagmati and its tributaries would be enormous.