Case Studies

Better Flood Models Begin With Better River Data

How Storm Geomatics supported the River Griffin & Upper Whitewater Mapping and Modelling Study with model-ready inland water survey data.

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The Background

Date: Summer 2026

Client: Jacobs

Storm Geomatics was commissioned by a client on behalf of the Environment Agency through the NGSA Mapping and Modelling Framework (2024) to deliver a comprehensive Mapping and Modelling survey of the River Griffin Stream and Upper Whitewater catchment in North Hampshire. The project objective was to provide hydraulic modellers with accurate, model-ready survey data to support Flood Modeller Pro and TUFLOW model development.

The River Griffin catchment contains a complex network of tributaries, drainage pathways, ponds, structures and floodplain features. Understanding the hydraulic connectivity between these elements was critical to ensuring reliable model performance and reducing uncertainty during model build and calibration.

Storm’s role was to provide accurate, model-ready geospatial data needed to capture that complexity.

A structure forms part of the hydraulic connectivity.

Process

The Challenge

Lead surveyor Tom Isaac was presented several challenges that could influence model performance if not accurately surveyed.

Extensive tributary networks
Multiple pond and drainage systems
Hydraulic controls and culvert structures
Watercourses crossing beneath major infrastructure corridors
Complex siphon arrangements
Dense summer vegetation obscuring channel form and asset visibility with temperatures at times above 30c.

The image below shows surveyors capturing features at a culvert control structure.

Structures such as these often have a significant influence on conveyance, water levels and flood extents, making accurate survey information essential for hydraulic modelling. Note the left hand arch in the photograph has been modified and has reduced capacity.

Surveying a hydraulic control structure to support accurate representation of conveyance and connectivity within the final hydraulic model.

Understanding Hydraulic Connectivity

One of the most valuable elements of the survey was defining how water moves through the wider catchment. Storm surveyors paid attention to identifying locations where watercourses interacted with transport infrastructure and complex syphon structures that influence hydraulic behaviour throughout the catchment, where the channel is culverted beneath an adjacent canal before returning to the surface.

Storm’s survey captured:

Inlet and outlet geometry
Headwalls and control structures
Channel tie-ins
Bank profiles
Local topography
Upstream and downstream connectivity

These details reduce the need for modeller assumptions during network schematisation and model construction.

Why This Matters to Hydraulic Modellers

Storm’s methodology focused on capturing features that directly affect model outputs. The purpose being to enable modellers to reduce assumptions, improve robustness of flood risk predictions and also to increase confidence in flow pathways. Ultimately, with better geospatial data better model outcomes are achieved.

Process

The Results

Storm delivered a complete package of survey information structured specifically for hydraulic modelling workflows, including:

CAD Cross Sections (XS)
CAD Long Sections (LS)
Structure survey data
XYZ coordinate datasets
Geo-referenced photography
Flood Modeller Pro outputs
TUFLOW-compatible data
EACSD deliverables

By combining specialist inland water survey expertise with a detailed understanding of hydraulic modelling requirements, Storm delivered a dataset capable of accurately representing channel geometry, hydraulic controls and catchment connectivity across the River Griffin and Upper Whitewater system.

As the UK’s only dedicated geospatial survey company focused exclusively on inland water environments, Storm understands the data hydraulic modellers need and the consequences when critical hydraulic features are missed.