Fluvial Design Guide - Chapter 1

Design of works in the fluvial environment


1.1 Scope of the guide

The scope of this guide is generally limited to what can be termed ‘interventions’ in the fluvial environment. This includes hard engineering and soft engineering as well as maintenance interventions such as de-silting and vegetation control. The fluvial environment includes not only the watercourse (bed and banks) but also the floodplain and immediate hinterland.

The guide is intended primarily for situations where flood risk management or land drainage is an important driver. It aims to support delivery of fluvial design in line with government policy as set out in Making space for water (Defra, 2005).

The fluvial system is illustrated in Figure 1.1. Although interventions in the fluvial system have greatest impact on the river channel itself, the wider impacts on the channel margins and floodplain must also be taken into account.

The impact of fluvial interventions extends beyond the physical environment to cover a wide range of uses of the fluvial system such as navigation, angling, walking, water supply and wildlife. In addition, the full extent of the fluvial system – as encompassed by the catchment – has a direct impact on the hydrology, geomorphology and ecology of the river – all of which are important inputs to the fluvial design process.

The guide covers all of these elements, though its primary focus is inland flood risk management. It does not stray into issues of land use management or surface water drainage in the catchment. At the downstream end of the fluvial system, the guide deals with issues of tidal influence, but does not cover saline water ecology, or waves in estuaries or on the coast.

Figure 1.1 The fluvial system

From source to sea, the fluvial system includes drainage channels and rivers, lakes, floodplains and washlands, and all the associated ecology and landscape.

The system also includes the flood risk management infrastructure, together with the infrastructure associated with other uses of the river, such as navigation locks.

The fluvial system is dynamic and changes with time. Understanding this is fundamental to the fluvial design process.


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