Fluvial Design Guide - Chapter 9 Background

Floodwalls and flood embankments

Charlie Rickard

This chapter provides practical guidance on two of the main structural elements used for flood risk management – namely floodwalls and flood embankments. Fundamental issues are covered and the two options (wall and embankment) are described and compared.

There is guidance on the selection of design crest level, with advice on freeboard and performance in flood conditions. Failure modes for walls and embankments are described and illustrated.

The chapter then provides separate guidance on walls and embankments. The section on walls covers types of wall, materials, joints, steel sheetpiling, and provisions for access though walls. The section on embankments covers erosion protection, side slopes, location, foundations, and landscaping.

The next section addresses foundation problems and the design of appropriate mitigating measures for walls and embankments. There is guidance on foundation weakness, seepage and uplift, and the design of a cutoff.

There is a separate section on temporary and demountable defences describing and illustrating the use of these in situations where a permanent structure is not acceptable.

The visual aspects of walls and embankments are discussed with illustrated examples of schemes where these structures have provided defence against flooding as well as enhancing the environment in which they sit.

The last two sections deal with the construction of walls and embankments, and their maintenance.

Chapter Structure

9.1 Introduction

9.2 Fundamentals

9.3 Wall or embankment?

9.4 Design crest level

9.5 Performance in floods

9.6 Failure modes

9.7 Floodwalls

9.8 Flood embankments

9.9 Foundations

9.10 Temporary and demountable defences

9.11 Visual aspects of floodwalls and flood embankments

9.12 Construction of floodwalls and embankments

9.13 Maintenance of floodwalls and flood embankments

Key references

Other references

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Case Study 9.1

Case Study 9.2

Case Study 9.3

Case Study 9.4

Case Study 9.5

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A floodwall that provides visual interest as well as protection against flooding

Charlie Rickard

C E Rickard
Independent Consultant
4 Millards Lane, Lode, Cambridge CB25 9ES
charlierickard@btinternet.com

Charlie Rickard has over 40 years experience in civil engineering hydraulics. He has been an independent consulting engineer since 2003, specialising in river engineering and flood alleviation. He has been a technical author for a number of hydraulic design guides, including CIRIA’s original Culvert design guide. He also has considerable experience as an expert witness, having worked on more than 15 cases, predominantly associated with flooding and land drainage.