2B Landscape Consultancy - Sustainable Drainage systems (SuDs)

SuDs Legislation update:

In response to recent storm events, flooding and climate change, the government has introduced the Flood and Water Management Act 2010 (Schedule 3). The Act is being implemented in stages, with the draft National Guidelines for SUDs currently being consulted on.

These guidelines will provide the criteria upon which SuDs Approving Bodies (SABs) will assess and comment upon drainage systems, at the planning application stage, for all new developments.

For more information, see DEFRA website here.

Sustainable Drainage systems (SuDs)

Sustainable Drainage systems (SuDs) are increasingly required components of developments. They integrate water management within new and existing sites - rather than obliging flood water to be dealt with 'downstream' - often with disastrous consequences. SuDs are designed to mimic the effects of natural drainage systems, thereby reducing and, if possible, eliminating runoff from a given site.

SuDs Components

The components form a 'management train' which is multi-functional and includes:

water treatment: via filter strips and porous elements;
water storage: in green roofs, swales, ponds and basins;
conveyance: water is moved using only gravity, in swales and ditches;
flow atttenuation: via control points.

Examples of these components are in the 'Gallery' to the right. Water is handled cleanly and safely - on the surface where possible - in a landscape designed for aesthetics, amenity and nature.

Are SuDs expensive and difficult?

Absolutely not!

SuDs have a history in the UK of being expensively over-engineered, but this need not be the case. As Landscape Architects, we integrate SuDs within the site design, from concept masterplan to detailed layout and implementation. When properly considered from the outset, good SuDs design provides safe and low-cost opportunities to:-

significantly reduce long-term management costs;
improve bio-diversity (which helps with BREEAM ratings);
provide social and economic benefits through improved aesthetics and function.

Our 2B landscape team has undergone recognised CIRIA design training to undertake SuDs planning and design work, in collaboration with other trained professionals.

We would be delighted to discuss your requirements, so do please get in touch.

Project examples:

Green Roof timelapse video

[video options: full-screen (recommended); HD to view in High-Def on Vimeo site]

This video shows the creation of a small green roof outside our office. Green roofs offer multiple benefits: biodiversity (we selected locally indigenous wildflowers and grasses, as well as some bulbs for early spring colour); durability (they protect the underlying construction); insulation (especially from summer heat); and they are beautiful to look at - constantly changing. They also store a proportion of stormwater and act as the first component of a sustainable drainage system.

Gallery of SuDs components

SuDs component: Green Roof

SuDs starts on the roof, as you will see from our video on the previous slide. A proportion of water can be held and released slowly to the lower levels of the SuDs 'management train'. This roof uses drought-tolerant Sedum species, but many other species can be used, including native herbs and grasses. (Floriade 2002)

SuDs component: Green Roof

Even as water is delivered from the roof, when kept in the open, it provides an amenity, as well as a retention and overflow capacity (York University).

SuDs component: Rain Chain

This is a playful way of conveying water from the roof gutter to the basin within the paving - a rain chain (Alnwick Gardens).

SuDs component: Permeable paving

Permeable paving can deliver water to open channels around the site, or, on very constrained sites, directly to underground water storage chambers (Innovation Park, Leeds).

SuDs component: Swale

A shallow swale is a simple, safe and attractive way to convey water from source to the larger storage elements. Here at York University, it is perfectly integrated into the landscape.

SuDs component: Pond

This shallow pond with reed-lined margins provides safe storage capacity as well as a permanent water feature for wildlife (Alnwick Gardens). Storage basins which are normally empty, except in flood conditions, are known as Detention basins.

SuDs component: Control and Reedbed

This reed-lined pond helps to clean the water as it passes through the SuDs system (Hopwood Services, M40). The inflow is at top left, see next image.

SuDs component: Control and Reedbed

In this zoomed view of the previous image, the piped inlet to the pond forms a control point, limiting normal flow rates from the preceding pond. However, a dry swale, above, allows water to overflow in extreme conditions.

Project: Power Station

Project example: Tansterne Power Station

This drawing describes how water is captured and processed from clean surfaces within the power station site (roofs), potentially dirty surfaces (hardstandings) and the surrounding farmland. It is then processed through a reedbed before running into a permanent pond.

Project example: Tansterne Power Station

This cross-section explains the relationship between the permanent water level of the pond, the 1:100 year storm level and the freeboard level defined by an emergency slipway.

Project: NHS Clinic

Project example: NHS Clinic

This NHS Clinic was seeking a BREEAM Excellent rating, as well as needing a cost-effective drainage strategy. We proposed a SuDs-based solution, which contributes to both requirements with a simple, low-maintenance, but attractive landscape proposal.

Project: Drainage Strategy

Project example: EASEL Drainage Strategy

Within the context of this substantial JBA drainage strategy for East and South-East Leeds (EASEL), we provided a number of landscape-led proposals, including: optimising Sustainable Drainage opportunities through creative use of greenspace; and micro-engineering the streets and footpaths to prevent inflow of flood water into vulnerable buildings, seeking rather to deflect them to soft flood storage areas.

North Cave Catchment Strategy

Project example: North Cave Catchment Strategy

North Cave flooded badly in June 2007, damaging 31 properties. Whilst there was a predictable reaction of 'build the defences higher and deeper', we sought to pursue a catchment-based strategy. This included reducing the influx of flood water from upstream; and using the natural form of the land to more safely direct water away from houses. The latter option has the backing of local landowners and we hope to see North Cave better prepared for future extreme weather events.

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