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Innovation & Research

Issue No. 53


Sub-standard shear studs Buildings

Coastal engineering CLASH project

Construction futures

Effective design management New standards for concrete

Lighting in hospitals New standards for concrete

French acoustic facilites Highways

Salt spreading on UK roads

8 4

Recycled and secondary aggregates 6 Environment

3 4

Recycled and secondary aggregates 6 Europe

2 4

Management of innovation The changing face of DFID research 5


Best practice for masonry façades 5 The value of UK-grown timber 7 Sub-standard shear studs

2 Structures Floor vibrations Waste Landfill linings on steep slopes 6 3

The value of UK-grown timber 7 Steel Designers Manual 6th edition 5


Best practice for masonry façades 5 Building envelope acoustics

7 4 May 2003

A best fit solution for side weirs Engineers at HR Wallingford and Mott MacDonald have developed a new design

procedure for side weirs as part of a project carried out under DTI’s Partners in Innovation programme. The design procedure, along with general advice on the correct use of such structures, will be published as a Manual by Thomas Telford this spring.


ide weirs divert flow from main channels into side channels when water levels exceed a given limit. In the UK they are used to:

• prevent flooding in rivers by diverting flow into temporary off-stream storage or diversion channels;

• discharge storm water at overflows in combined sewers;

• divert or divide flows within water and wastewater treatment works;

• discharge excess flows from canals and navigation channels.

Overseas, side weirs are also used to regulate flows in irrigation systems. Though side weirs are important water control structures, their hydraulic design is complex. Flow conditions vary with distance along the weir and do not conform to simple weir theory. Richard May of HR Wallingford coordinated HRW’s input to the Manual. ‘We analysed published data from 470 separate tests on

(Top) River Exe side weir with no flow and (Above) in flood

side weirs in order to identify the key issues affecting their performance,’ he explains. The data were used to calibrate coefficients in the momentum form of the one-dimensional flow equation that describes flow over a side weir. Numerical solutions of this equation were then used to extend the range of flow conditions considered and also to develop simplified prediction methods.

The results from the study are presented as graphs and equations that can be used to determine directly the amount of flow spilled by a side weir and the overall variation in water level along the weir. The Manual also includes

more-general chapters covering the layout, operation, maintenance and safety of side weirs, and should be a useful tool for anyone dealing with the design of such structures. HR Wallingford is organising a one day Workshop on Side Weirs and Culvert Design during 2003. For further details including registration, please contact Jackie Harrop on 01491 822389 or visit

For further information please contact Richard May (01491 822251; E-mail:

Innovation & Research Focus Issue 53 MAY 2003 1

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