GREEN & BLUE INFRASTRUCTURE
GREEN-TECH SUPPLIES CUSTOM BIORETENTION SOIL TO EXPERIMENTAL CITY CENTRE RAIN GARDEN
Two of the best and most costeffective ways of dealing with rainwater and runoff are green roofs , or at ground level , rain gardens . Rain gardens are one of the leading types of Sustainable Drainage Systems ( SuDS ) put in place to try to mimic water run-off as closely as possible to that in the countryside .
Liverpool Rain Garden . Credit : Dan Dean Photography
Background : Liverpool is England ’ s third largest city with a rich industrial heritage . However like many cities , it has suffered its fair share of urban decline . Over the past few decades there has been a flurry of redevelopment initiatives to address this decline , all placing Liverpool firmly as one of the UK ’ s up and coming business destinations .
The urban rain garden at Upper Pitt Street , is an exemplar project ( 100 % externally funded through the EU URBAN GreenUP project - www . urbangreenup . eu ), showcasing how landscape design combined with SuDS principles can be successfully retrofitted across our cityscapes .
Green considerations : As part of any urban regeneration , it is vital that consideration is given to the green infrastructure . The benefits are many ; from the cooling effect from trees , both from the shade and the moisture they give off through transpiration or the filtering of pollution and carbon sequestration via the leaves and the substrates ; and the attenuation of rainwater , slowing down the flow of storm water into our overburdened drainage system . In addition , the potential for added biodiversity ; the added shrubs , trees or wildflowers providing vital habitats to bees , insects , and other pollinators .
Like bio-swales , rain gardens are designed to take water runoff from impermeable surfaces such as roads and pavements . They filter out contaminants and debris such as silt and vehicular contaminants washed off the road surface by rainfall , whilst holding onto the excess water and slowing down the release , which in turn reduces the pressure on the storm drains . They are effective in removing up 90 % of pollutants , and up to 80 % of sediments from this surface water runoff .
Liverpool ’ s urban rain garden is designed to partially attenuate water within Polypipe ’ s ‘ Permavoid ’ underground storage crates . This stored water provides passive irrigation to the vegetation above , as well as storm water attenuation .
Rain gardens will usually feature plants that can withstand waterlogging up to 48 hours at a time , as most swales will drain over a period of 12 – 48 hours . Large feature rocks and pebbles also help in the filtration process . For the urban rain garden in Liverpool , plants were chosen for their drought resilience , to suit the specially blended freedraining nature of the substrate .
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