Can technology assist NFM (Natural Floodplain Management) and by extension SUDs solutions?
Natural Floodplain Management (NFM) is an emerging solution that is gaining traction with communities and the Environment Agency for a number of reasons aside from simply Slowing the Flow of impending flood events.
A natural approach to flood management such as the introduction of beavers, leaky dams and the restoration of wooded areas and moorlands has many aesthetic and environmental benefits as well.
We are certainly advocates of planting more trees but in the short term we are not going to see any reduction in flow rates from this activity, until they reach a certain maturity and we certainly cannot plant enough trees in suburbia to make any sort of impact to flow rates.
But rather than restricting the NFM solutions to being purely natural why not consider a technology that mimics nature?
EGRP (Energy-passive Groundwater Replenishment Pump) is one such technology we are attempting to introduce into the NFM and SUDs spaces.
Conceptually it is a simple system which comprises a number of plastic rods being bored into the ground at various depths between 1.5m & 12m.
The first stage is an ISO 22282-2 Geo-hydraulic infiltration test drilling exercise to ascertain the local Drainage Design Rate.
Once this has been identified stage 2 is the production of an engineering Drainage Design Statement (using industry standard software) detailing the half drain-down times within a 24 hour period, for a chosen storm event (with an allowance for Climate Change).
Finally the system design is backed by Groundwater Dynamics’s Professional Indemnity Insurance with warranties signed off for Local Authorities by their engineering partners.
Natural Floodplain Management
Unlike NFM, EGRP solutions can be designed and measured to give exact absorption and therefore attenuation rates to slow the flow into downstream areas by taking the water below ground.
Pictures taken by Groundsman at Edgbaston No1 Practise facility
But like NFM, EGRP mimics nature and the structure of piles inserted into the soil act very similarly to that of the root structure of a mature tree. The key difference being that EGRP can achieve these results in 12 weeks rather than the 12 years a mature tree would need to match these results.
How it Works
Each EGRP is installed 100mm to 750mm below surface level and it takes up to 12 weeks before the system begins to work. Water moves horizontally in poor draining sub-soil and the EGRP acts like an elevator shaft taking water down to lower unsaturated levels where it finds its way into the soil strata via fissures which build up around the system.
Of course, like all solutions, it is not a panacea and will only work in the right geological areas, as we have discovered through numerous test bores at proposed sites, but where the conditions are right EGRP has proven to be a great solution in dealing with surface water flooding.
There are numerous case studies to show how this has worked in the sports arena where Groundwater Dynamics are working with some very happy ground staff at numerous high profile sports arenas across the UK.
NFM is an obvious fit for EGRP in rural flood attenuation solutions but due to its unique attributes (no maintenance, management of pollution and low planning requirements) it is also ideal for urban SUDs solutions.
It is being incorporated into natural solutions such as swales and soft landscaping for new developments. It can be installed under permeable paving & tarmac/concrete to increase the capacity of these solutions and it can be installed in conjunction with linear road drainage systems to amplify their discharge rates into the subsoil rather than the drainage network.
EGRP reduces the impact on existing infrastructure because it is moving the surface water from the skies to underground aquifers and natural storage areas deep in the subsoil.
Indirect to Ground Infiltration
Each EGRP device is first of all capped and then positioned at 300mm to 600mm below ground level with storm water entering the system laterally and not vertically.
Where the EGRP system is receiving storm water from roads and/or parking bays then a number of measures are taken to ensure that sufficient levels of treatment are designed into the SUDS design solution for example;
Baffle & Wier Gulleys
Permavoid Bio-mat crate system
Inbitex Bio Geo-textile
All three of these examples are proven effective barriers against hydro-carbon contamination entering natural ground water systems and form only part of the overall SUDS treatment train.
The picture below shows a 6m EGRP device being installed (wherever the depth is 6m or deeper, 3 devices are interlocked together to form a more powerful device).
Imagine how EGRP can benefit your scheme
Imagine the benefits to a builder on a new site when he can obtain his SUDS licence by installing a small EGRP Rain Garden in a small plot that can (with careful design) cope with the surface water for the whole development and without any connections to the main drainage network.
Imagine designing a system for a supermarket or business park carpark capable of dealing with 100% of storm water at source without having to connect to public storm water drains or combined sewers & saving huge fees payable to the local water company.
Imagine hundreds of new NFM schemes with engineered absorption systems and the benefits that can bring to enabling the solution for deployment in suburbia.
Closing the Flood:Drought Cycle?
Then think about the added benefits of an Energy-passive Groundwater Recharge Pump (EGRP) system that actually returns surface water underground and, as it says in the title, replenishes (recharges) groundwater supplies at source.
What impact can that have on agriculture, drought prevention, over-abstraction rates and the sustainability of our water supplies?
These are just a few ideas of how EGRP can transform our relationship with water and address many areas of legislation and planning in the UK & Europe – Making Space for Water – Slow the Flow – SUDS.
Groundwater Dynamics is now in its seventh year and has successfully installed over 250 storm water management schemes. As Principal Designer and a full blown construction company, Groundwater Dynamics provide PI backed system design and a full construction solution dealing with clients storm water management requirements throughout the whole process of design & delivery.
If we have piqued your imagination do get in touch with us at www.aquobex.com or +44 (0) 1923 518582