Table 3-3: Overview of basic model types 3.7.1 Selection of Modelling Software A variety of hydraulic modelling software is available for use in flood model development although there is no universal package which can be recommended for all applications. The Environment Agency has carried out benchmarking tests of 1D and 2D hydraulic modelling packages commonly used in Flood Risk Management in the UK (Crowder, et al., 2004) (Neelz & Pender, 2013). These provide a summary of the key features of the modelling packages and the time taken to set up models using different packages.
It is not advised that software should be used unless it has been thoroughly peer reviewed or extensively tested through an extended period of use by several different organisations. Advice should be sought from SEPA if the suggested software is not covered by the Environment Agency benchmarking, including where the use or development of novel tools is proposed in developing areas of flood risk science such as Natural Flood Management or Climate change. In any tender the contractor should set out which modelling software will be used and why it is appropriate to meet the project objectives.
In addition to the ability of the selected software to meet the project objective the Responsible Authority should consider: If there is a sufficient pool of people in the industry experienced in using the selected software to enable the model to be reviewed and audited If use of the proposed software will restrict future use and development of the model to specific contractors, either because the software is in-house to a particular contractor or because there are limited skills. If there is support and training available for use of the software to allow any bugs or issues to be addressed and for expert advice to be sought for difficult or unusual schematisations.
Licensing options and cost if the Responsible Authority either wish to rerun or update the model themselves or to view the model schematisation and results. However it should be noted that higher license costs may add functionality necessary for meeting the project objectives or be offset by improved workflows, customer support, Flood Modelling Guidance for Responsible Authorities v1.1 20 Model Type Description and Uses Steady Flow In steady state modelling it is assumed that flow does not vary with time at given location. This assumption can be made for many applications where floodplain flow is limited, for instance in narrow valleys.
Unsteady Flow Unsteady models allow flow to change with time. Unsteady models are required for problems where flood wave propagation or flood storage or attenuation within the system is of interest. The areas where unsteady flow should be considered include where: • there is a tidal boundary; • there is flood storage within the system; • hydrograph timing is of interest; • floodplain flow needs to be taken into account; • there are pumps or gates to which control rules are applied.