The new Science Block at Bewdley School was an opportunity to create a dynamic learning landscape that puts the flow and qualities of rainwater at centre-stage. When it rains, a waterwheel, giant Torricelli tube and a tipping bucket all demonstrate scientific properties of water before feeding into rills, wildlife pond and raingarden that enhance the setting of the new building and provide valuable educational resource.
The project aimed to provide flood prevention capacity through interception and attenuation storage, while also enhancing the landscape and providing educational opportunities through access to the flow of water.
The design provides an attractive and useful series of features with educational benefits for the school pupils, whether in lesson time or during breaks, appropriately for the nature of this Science Block area.
The SE elevation of the building opens onto the ‘Science Garden’: an attractive paved area adjacent to the classrooms with meadow lawn area beyond, contained by a mixed native/ornamental hedge and low timber fence.
Also on this side of the building, rainwater flows from the roof via aerial channels to three hydraulic demonstration features that drop the water into a rill channel. One feature demonstrates the effect of increasing water column height on jets of water squirting out of the pipe; a second uses a tipping bucket to allow students to determine the rate of flow coming from the roof; the last uses a simple water-wheel to demonstrate the power of flowing water.
Where water arrives at the raingarden, via two aerial channels, threaded fixing points have been provided at the channel openings, allowing students to design, construct and experiment with various ways of transferring water flow.
The site has been divided into four discrete sub-catchments: two roof planes, the new plaza and part of an existing tarmac playground.
The roof has two planes falling in opposing directions, which has given rise to two distinct flow paths for roof run-off: one to the NW side and the other to the SE side. Rainwater is collected from the building's roof via five aerial channels and three sett channels that intercept the flow from the roof’s rainwater pipes.
This run-off is slowed by collection and conveyance in a series of channels, rills, and grass swales, and stored in open basins, raingarden, rill and pond. Both flow paths combine at the S corner of the building before entering the main storage swale running along the SE footpath link toward the brook.
A paved plaza in front of the building, which may experience occasional vehicular use, utilises permeable block paving to treat and store the rainwater that lands on it before releasing, via a Controflow flow control chamber, into the main storage swale.
The combined flow from these three sub-catchments is conveyed and stored within the main swale, where it is joined by run-off from an existing playground area flowing into the swale at the surface over a flush kerb. The combined flow of all four sub-catchments slowly flows along the main swale toward the Riddings Brook and discharges into the brook via a final flow controlled basket outlet.
The SUDS scheme has been designed to manage water on the site for the 1 in 100 year storm plus 30% allowance for climate change effects. The design provides for an initial loss of 5mm of rainfall from 'interception storage'. The loss occurs through evaporation, soakage into the soil and transpiration through vegetation, following the behaviour of natural systems. Some additional attenuation is likely to occur through infiltration of surface water within permeable pavement and all soft landscape features.
The system discharges into Riddings Brook at the Greenfield Runoff Rate: 7.3L/sec/hectare.
Aerial channels and surface-level sett channels carry run-off from roofs and ground surface to two rill channels, one on either side of the building.
The planted rill channel is an architectural feature running along the front elevation of the building that conveys water flow whilst providing a dramatic planted linear element at the foot of the building. Bridges allow access over the rill. Timber bollards and strategically-placed benches deter people from walking into the rills.
A second, unplanted rill channel runs the entire length of the Science Garden, parallel to the building elevation, demarking the transition between paved area and the wider meadow garden, picking up run-off from these paved areas. Integrated bridge crossings allow access to the wider garden. As the rill fills with water, small gaps in the sides of the rill allow some water to flow into a tree planting trench in line with each tree, providing irrigation.
As the flow continues along the rill channel, a small weir set in the channel diverts water toward the wildlife pond. The pond is lined to maintain standing water to support aquatic life but has a wider 150mm deep storage zone over the standing water level.
Location: Bewdley, Nr. Kidderminster
Return Period Attenuated: 1 in 100y (+30%)
Techniques: aerial channels; hard rills, planted rills; raingarden; wildlife pond; shallow basin; permeable paving; storage swale; sett channels
Discharge Destination: Riddings Brook
Discharge Flow Rate: 7.3L/sec/hectare
Client: Worcestershire CC