Green Engineering

Plant the Flood Plains – do it now

Amid the news that the government will tomorrow announce plans to over-ride Planners on local councils who fail to deliver on housebuilding targets, calling them NIMBY (not-in-my-back-yard) and BANANA (build-absolutely-nothing-anywhere-near-anything), my line of work prompts me to think about the potential impact of large scale building on our priceless green infrastructure. It also prompts me to think we all deserve a better government but that’s another issue altogether.

I’ve deliberately not used the word ‘environment’ because there’s an unexpressed line of demarcation between the realms of construction and environment which tends to place the two things on irreconcilably opposite sides. This is not helpful. Here’s something to consider….

Alongside a requirement to build 1 million new homes in England by 2020 (that’s less than 2 years away) there surely needs to be a hand-in-glove relationship built between construction and our partner in secure existence, green infrastructure? We all know that costly ‘natural’ disasters such as severe flood events can be exacerbated by drainage overload where new developments have simply been connected to existing drainage systems. One of the best, if not one of the only effective solutions to this, are creative SuDS solutions (Sustainable Drainage Systems) – think peat bogs and heather moorland, broadleaved woodland, wildflower meadows, reed beds and in the urban landscape water-retentive towns, green rooves, rain gardens https://raingardens.info/, SuDS associated urban tree planting, temporary wetlands https://freshwaterhabitats.org.uk/wp-content/uploads/2013/09/WETLAND.pdf and other landscape features.

Such solutions, where implemented to a sufficiently high standard, provide valuable wildlife habitat, include planting at a healthy scale and, at the macro end of things, can involve the up-stream planting of new woodlands specifically to help reduce peak river flows through towns and cities. A couple of things to remember in this context; the presence of mature trees greatly reduces soil erosion and creates a climate in which micro-organisms can thrive. A single mature tree can absorb as much as 48 pounds of carbon dioxide in a year and can, via transpiration, extract up to 100 gallons of water out of the ground in a day.

I’m driven to the conclusion that it isn’t so much a resolution of the tension between intensive housebuilding and protection for our green infrastructure that we need, but a fully integrated reconciliation of both in acknowledgement of their critical interdependence.

The River Ness Rises

The more tree cover we have, on river banks, in towns and cities, on flood plains, the greater the reduction in flooding. There is of course a troublesome time-lag. For trees, around 25 yrs of growth is required before these benefits begin to kick in. It’s difficult to overstate the importance of having recognized guidelines to work to on these issues. Taking replanting requirements in specific directions is impossible without a commonly recognized framework that can be promoted, overseen and evaluated. I wonder then how quickly we can hope we will see cohesive, well-targeted green infrastructure policies attached to what has become an urgent need for more house-building? Or will we simply end up building with the blinkers on while the waters continue to rise?