Photograph - Weir River Itchen, Winchester

Weir on a subsidiary channel of the River Itchen, just upstream of Wharf Mill, Winchester, Hampshire.

1D Hydraulic River Modelling

Uses of River Modelling

We can undertake 1D hydraulic river modelling using Flood Modeller Pro (formerly ISIS) or HEC-RAS software and this is often a component of other engineering processes. For instance, hydraulic river modelling can be an important input into the more detailed Flood Risk Assessments or Flood Consequence Assessments.

We often use 1D river modelling to assess if a proposed development would be likely to suffer flooding from an adjacent watercourse. Other uses of hydraulic river modelling includes:

Environmental Impact Assessments
Flood mapping
Investigation of river flooding problems
Design of flood alleviation schemes
Design of structures situated on or in river channels (bridges, culverts and weirs)

1D River Modelling

The use of 1D and 2D, in terms of river and flood modelling, refers to the flow of water. So for 1D modelling the water flows in one dimension along the watercourse while in 2D flood modelling the water can flow in any direction across the ground surface.

Flood Modeller and HEC-RAS software allow the 1D modelling of watercourses including associated structures such as culverts, bridges and weirs and can represent steady, unsteady, supercritical, subcritical and transitional flows. The software therefore allows the estimation of water levels under various flow conditions which is necessary for the prediction of the onset of flooding and the design of subsequent improvement works, if required.

Input Data

An important source of input data for hydraulic river modelling will often be a Flood Estimation Handbook (FEH) hydrological assessment of flood flows in a watercourse. Further input data will be required including cross-sections and levels along the watercourse channel. These are often obtained by carrying out a topographical survey and if required, we can plan, organise and supervise this as part of our service. A further source of ground level information is LiDAR data, see 2D Flood Modelling.

2D Flood Modelling

An alternative to 1D River Modelling in some circumstances can be 2D Flood Modelling. While the former requires the watercourse channel to be represented by a series of cross-sections, the latter models water flow over a representation of the ground surface with x, y and z co-ordinates. 1D and 2D software can be used in conjunction to represent watercourses with extensive flood plains, see 2D Flood Modelling for more details.

Further Information

Flood modelling work is site specific so please contact us for further information including a free no obligation quotation.


Drainage for New Developments

Expert Witness

Flood Risk Assessments

Flood Consequence Assessments


River Modelling

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