Flood Modeller is a hydraulic modelling software package developed and maintained by Jacobs (formerly HR Wallingford and Halcrow). Previously known as ISIS, it has been the Environment Agency’s preferred 1D modelling software for decades, and a significant proportion of the EA’s existing river models are built in Flood Modeller.

The software provides:

1D hydrodynamic modelling: Full unsteady flow simulation through open channels, incorporating a comprehensive library of hydraulic structures (bridges, culverts, weirs, sluice gates, flap valves, and pumping stations)
Integrated 1D-2D modelling: Linking the 1D channel engine with the TUFLOW 2D engine for combined river channel and floodplain analysis. This linked approach is the standard methodology for many EA-commissioned flood mapping studies.
Flood mapping: Built-in tools for generating flood extent, depth, velocity, and hazard maps from model results
Scenario management: Efficient handling of multiple design scenarios including climate change allowances, defence breach, and blockage tests

In UK practice, Flood Modeller is commonly encountered when:

Requesting existing EA models for a Flood Risk Assessment — the majority of EA 1D river models are in Flood Modeller (ISIS) format
Undertaking detailed river modelling where the EA or LLFA expects results from an EA-standard model
Updating or extending existing flood mapping studies that were originally built in ISIS/Flood Modeller

Aegaea’s modelling team is proficient in Flood Modeller for 1D and linked 1D-2D studies, enabling us to work with existing EA models and deliver outputs consistent with national flood mapping standards as part of our flood modelling service.