Manage Stormwater with Green Infrastructure
by Oscar Warmerdam on Wednesday, October 2, 2019
Expensive urban stormwater management!
Imagine taking a big bag of 12,000,000-dollar bills and bury them. Yes, $12,000,000 in cash, and bury it underground for it never to come out again.
This is what we do every day when we route and detain urban stormwater by old, traditional means. We spend gobbles of money on stormwater management and engineering with little aesthetic or economic benefit.
$12,000,000 is the budget a civil engineer stated for pipe & tank-based stormwater management of a new 26.3-hectare (65-acre) property. Let that sink in for a while: $12,000,000!
To be honest, nobody ever says “thank you” to the civil engineer for the marvel of engineering each time they flush their toilet, or when the stormwater runoff hits the drains. It’s gone...taken care of by some underground, unknown entity. Completely taken for granted.
We are so used to defaulting to pipes and underground vaults that we have overlooked what could be done instead.
Pipes and stormwater management
A pipe is simply an underground river that no one can see. As it cannot spill, it needs to be extra-large in order to handle any unforeseen intense rain events, and even though I do not want to discredit the craftsmanship and engineering required to put this all together, once it is covered up with dirt, asphalt or concrete, it is completely forgotten.
It is $12,000,000 buried with no additional value beyond its core functionality.
Stormwater management from the past today!
In the early 1900s, a lot of smelly city streams and small canals were converted to pipes so that the residents would not see the stormwater discharges. Especially, as most cities were equipped with combined sewers mixing stormwater and municipal sewage. These pipe-based management practices reduced the odor and closed canals meant more space at street level to drive on.
In many cities, these days, some of these storm-drain canals are being ‘day-lighted,’ meaning they reveal the stream or canal once again by opening up the pipe and turn it back into a pleasant stream.
Natural stormwater management
Natural streams do not smell. The use of surface water streams allows vegetation to use up many of the nutrients and organic materials which leads to improved stormwater quality without any effort from anyone.
We can enjoy the cooling effect of the vegetation, and we have improved water storage and routing capacity.
As a bonus, the vegetation simply looks pretty. If you have some time, take a look at the stormwater management solutions in, for example, Cardiff or Edinburgh - beautiful creations!
But there is more! Water also tends to run more slowly through green infrastructure, so it has a slowing-down effect. It also puts us in touch with water again.
We humans cannot live without water, so why do we want to hide it? We should expose, treasure, and enjoy it.
Most cities take this a step further; they want their rivers to be swimmable again. They want people to go to downtown Grand Rapids Michigan and swim in the river. Imagine that! Would that not be super cool?
The future of stormwater management
When I was talking to a developer recently, I asked about the project stormwater management costs, and he said $12,000,000 in pipes and tanks. Moreover, I posed the question: “Why!?”
I asked why they did not route the water above ground through streams and canals instead of the pipes? This way, he will be spending less than the $12,000,000, but every dollar spent is offering an equal dollar in added aesthetic enhancement value of his property.
Now it rains, and we get rid of the water immediately in pipes. Then we run irrigation the next day because the trees and shrubbery need water. This is nonsense.
Tying in trees, shrubbery, and planters alongside shallow streams and canals that run throughout his streets and parking lots will bring birds, bees, butterflies and PEOPLE to street level where they can enjoy the space.
It will reduce the amount of water that needs to go to the municipal separate storm sewer system by 50%, and it can re-charge aquifers under a city.
Vegetation cools the development, dampens the sound, and increases the desirability and rent in that development. Sure, it takes maintenance, but anything desirable and worth keeping takes money to maintain.
The savings in green infrastructure can pay for many years of maintenance.
Green infrastructure is a sustainable stormwater management tool
Green infrastructure saves money for the developer, the cities become cooler, greener, and there is less water to clean. The occupants are lining up to shop, dine, and live there.
Putting water in a tank or pipe is a waste of resources, and we are shooting the water to a part of town where they can clean it, and then pipe it back again to water the plants.
- Don’t do a tank, do a Blue-Green or Purple-Roof instead.
- Don’t do pipes but do bio-retention and streams instead.
- Don’t do stormwater tunnels but do patios and parking lots that are permeable or temporarily floodable so that the water has a place to stay while the streams empty.
Use your imagination, and let the experts help you with the implementation! There are plenty of civil engineers that can help you bridge this quadrium.
So, the next time you want water to escape somewhere, and you default to a tank or a pipe...think of all that money you bury. Without any additional benefit. It simply is an opportunity lost.
Go green, folks!
- Oscar Warmerdam, President Purple-Roof
Purple-Roof is a NON-proprietary specification and not a product in itself. We are data-driven and base all our recommendations on hundreds of tests conducted by Green Roof Diagnostics. Read more about GRD in our blog article: Data-Driven Green Roof Research