Richard Hughes - Enzygo

Ask the Expert: Advancements in Hydraulic Modelling

4 October 2021 By

Richard Hughes, principal hydrological modeller at Enzygo, discusses advancements in flood modelling.

Enzygo Ltd are an independent, multi-disciplinary environmental consultancy with a proven track record of delivering creative, integrated and cost-effective solutions that maximise the potential of development sites. We use a collaborative approach to devise solutions that are respectful of technical and budgetary constraints, comply with industry guidance, whilst also fulfilling planning and commercial aspirations.

We have substantial experience in the delivery of all types of developments, including major infrastructure projects, residential housing schemes and renewable energy programs, across a broad range of environmental disciplines, including Planning, Air Quality, Hydrology and Drainage, Permitting and Regulation, Landscape, Ecology, Transport, Geo-Environmental and Hydrogeology, Noise and Vibration, and Arboriculture.

Richard Hughes, our Principal Hydrological Modeller, has 19 years’ working experience of the surface water environment and flood risk since initially joining the Environment Agency in 2002. Within this time, Richard has gained extensive experience of high and low flow estimation, hydraulics and hydraulic modelling, flood risk data interpretation and technical problem solving through both regulatory and consultancy work.  Below he discusses advancements in flood modelling.

The definition of a model is ‘A three-dimensional representation of a person or thing or of a proposed structure, typically on a smaller scale than the original’.

When we talk about flood risk hydraulic modelling, we are talking about trying to replicate or predict flood events that could impact upon property and infrastructure. We aren’t talking about physical models made of clay but sophisticated computer simulations that utilise detailed input data to covert flood flows and levels into flood extents and associated parameters such as velocity and hazard within a watercourse or waterbody and its associated floodplain areas. Modelling allows us to try and predict the future and to prepare for the day when, not if, that once in a generation flood event will occur.

The number of easily developable sites, outside areas of flood risk, are now diminishing and as such, attention turns to the viability of Sites that would have been previously overlooked. Often, mapped flood zones, such as those shown the Environment Agency statutory flood map for planning ( are defined through high level ‘indicative modelling’ that essentially highlights the need for further consideration. This high-level modelling lacks such detail as accurate channel representation and inclusion of bridges and culverts. The adage ‘rubbish in rubbish out’ is particularly applicable to flood risk modelling.

This is where detailed hydraulic modelling becomes essential to unlock the potential of a Site but also provides a tool to assess the impact of development proposals to ensure compliance with local and national flood risk policy.  The definition of flood risk shouldn’t be confined to an area of ‘blue’ as shown on regulator produced flood maps.

Hydraulic modelling has historically been seen as an expensive, onerous, unnecessary task that was often avoided by developers if possible. However, in a country where awareness of flood risk and impact of flooding is greater than ever, it is not only the regulators that keep a close eye on developments and their subsequent impacts. Demonstration of policy compliance and project neutrality, or even better ‘betterment’ goes a long way to allaying the fears of the aware.

Hydraulic modelling software is undergoing constant development and improvement in order to cater for the increased demand for demonstration of impact, meet the needs of time constrained projects through faster run times and provide a more user-friendly experience as well as providing a huge array of outputs in an easily understandable, visually recognisable format. These advancements, coupled with more powerful computers, now mean that a budget friendly model can be produced efficiently without significantly extending project timescales.

Here at Enzygo we are finding that more and more of our projects require hydraulic modelling of some description.  Models may range from simple channel and structure capacity checks to large complex multi watercourse models, and we have invested in our computers and software in order to provide a modelling service irrespective of the complexity.  Our experience in hydraulic modelling has enabled several sites to maximise their developable area whilst not increasing flood risk.