Hamilton A formal case study is currently being prepared by CIRIA This is a short guide . Hamilton is a good case study – it is one of the oldest SuDs schemes at this sort of scale – and it has fared well. Recently there have been political issues re their non-adoption and the attendant service charge

Key features of the scheme There are a series of swales and a wetland detention area. It is predominantly site control of storm water. The system was designed to; – create a sustainable and attractive network of channels and rills that allow for natural soak away and controlled flow to the brook. Why did Hamilton come about in the way it did? The Melton brook is subject to flooding and there was a requirement to limit water entering the brook. There were also ecological consideration; to build on the existing ecological value of the site.

Comments on the system Generally: great groundbreaking scheme that still looks good today But; no source control – this would have limited the amount of water entering the swale system and improved the quality – issues around scouring, also extensive use of stone rip-rap and gabion mesh to base of swales Issues Levels One of the contributing problems is the need for swales to get beneath roads; but despite this there are still lots of areas where the actual level of the bed of the swale could have been higher and slopes reduced This would benefit both the appearance, the amenity value and the maintenance

Picture shows dramatic level changes between amenity grassland and swale side slopes Longitudinal slope is too great to allow vegetation establishment And in some areas is causing scour See picture right

If the lengthwise gradient was less along the main swale planting would establish in the bottom of the swale – again looking more attractive, reducing the need for metal gabions and thus being safer and increasing biodiversity value. (a final benefit is improving the quality of the water) Extreme slopes also make mowing difficult.

Good levels

In this swale the longitudinal gradient allows vegetation to establish creating a more attractive, ecologically rich and safe local landscape.

Engineering Headwalls – expensive – these probably cost £2-3000 and are a big health and safety risk as well as being visually intrusive – there are better engineering solution that could be used – although what should happen is less water entering the system (better source control) – so could just have simple outfalls

This is adjacent to a footpath used by children en route to the primary school

This combined with the use of stone, gabion mesh and stone rip rap presents a real safety hazard

Amenity areas Some of these detention areas provide potentially sound kickabout areas – but not if they are wet across the whole base of the pond area. There could be simple ways to improve this in-situ; for example the depression to the north of Sandhills Avenue – if a shallow channel ran along the northern rim this would further drain this area to provide dryer areas for play and create permanently damp/wet areas for biodiversity.

Area north of Sandhills Avenue With a bit of work this could works well as a kickabout area

Land south of Sandhills Avenue – potential for safe ball play – steeper slopes near the swale are a problem

Planting beside the swales – in some locations it creates risk by permitting narrow access along the top of the swale bank – which would not be such a problem is the actual levels were gentler

Turning backs on attractive landscapes

The landscape is attractive and safe; yet there is almost no access to it and the garden brick wall emphasizes houses not relating to the swale area

Attractive and ecologically rich areas

There a series of ponds in the lowland area that are increasingly being colonised by invertebrates and flora. There is also local interest in the sites developing wildlife value.

Maintenance Do the maintenance people understand aims – there are areas where establishing reeds and wet grasses are being mown – would be better to leave

Allowing the vegetation to establish on the steep bank sides would reduce areas of difficult mowing and also improve potential biodiversity and filtering capacity