Comment: From drainage to stormwater management
As cities take over as the dominant way of life, continuing to use drainage as a waste disposal system is a recipe for disaster - stormwater drainage needs to become stormwater management, writes Paul Davies
by Paul Davies, Global Surface Water Skills Leader, Arup
Drainage has always been looked upon as a poor relation in engineering, and unsurprisingly, it’s not a common topic of conversation in polite circles. However, I think it should be – because we need to radically rethink our approach to drainage if we want to live sustainably in cities.
The volume of water we drink is insignificant compared to the volume of water we consume. This is not sustainable. For some time, I have believed that turning rainwater into a waste product to be discarded down the drain, whilst at the same time using treated water to water the lawn or irrigate land, has got to be some form of insanity.
The drainage industry has evolved over the last millennium to take our discarded water away from us in the most efficient manner. Its main purpose is to enhance our convenience by making our waste products disappear.
Over time, drainage has become very efficient as a waste disposal system, which hides many of the problems we are creating by moving them downstream, out of sight. Yet drainage is not protecting us from flooding or droughts. In fact, it’s making flooding and droughts worse.
Currently stormwater drainage aims to take water away from us as quickly as possible. So the system collects water together, which concentrates both the flow and whatever it picks up on the way. Then we transfer these flows to the receiving system much earlier than they would have arrived naturally. Effectively dumping these concentrated flows into rivers more quickly makes it much more likely the river will be overloaded – in terms of both water quantity and quality.
Considering the other side of the coin, large areas of low permeability (such as streets and buildings) reduce the amount of stormwater that can get into the ground. Drainage disposes of this water very efficiently too, transferring it to the receiving system and depriving the aquifers of this water, depleting them.
What’s the answer? Stormwater drainage needs to become stormwater management. Stormwater should be captured, recycled, and stored for a (not) rainy day. The Hunters point area in New York is a good example of what can be done, as is Greener Grangetown in Cardiff. Keeping water local in this way could also save some of the huge costs incurred moving it around.
Achieving this requires a change in mindset. We must think of stormwater as the most precious resource we have, and not something to be discarded as a waste product. Stormwater management should not just be a way of making water go away; stormwater is what keeps us alive.
Cities do not yet manage water very well and need to do better. As cities take over as the dominant way of life, continuing to use drainage as a waste disposal system is a recipe for disaster. If cities do not become more self-sufficient they will suck the drinkable water out of the rest of the planet.
- Read more from Paul Davies and his colleagues at Arup on the Arup Thoughts blog:
- Getting to the bottom of the infiltration challenge The infiltration of groundwater into sewers and other infrastructure presents a major burden for water and sewerage... Read More >
- Retro approach suits Welsh Water Threat of EC action over sewer spills at the Burry Inlet in South Wales prompted Welsh Water to adopt a retrofit sustainable... Read More >
- Spa town saves on major infrastructure An innovative approach to drainage in historical Leamington Spa has made 80% efficiency savings, says European... Read More >
- Project Focus: Smart flood alleviation system protects Portsmouth A smart hydrometereological system was installed to monitor flood risk in the south coast city, with real-time sewer level... Read More >
- Project Focus: Canals provide capacity for 21st Century flood protection A 19km stretch of canal near Glasgow is to be given a stormwater drainage role, in an innovative project which... Read More >
- Digging Deeper: Property level flood protection A whole catchment approach to flood risk should include protection at the level of the individual property, writes... Read More >
- Getting to Grips with... hydraulic drainage design To achieve an accurate hydraulic design, it is essential to make correct assumptions about the behaviour of pipes over... Read More >
- Interview: Tony Harrington, Director of Environment, Welsh Water 'Across the EU, sewerage remains the Cindarella service... we all need to do something about this together if we are to... Read More >