Flood forecasting for the River Ayr and Annick Water

JBA Consulting

We were tasked to develop a new flood forecasting model and warning thresholds for the River Ayr and Annick Water in

Ayrshire, Scotland on behalf of SEPA. As part of this project, we needed to recalibrate SEPA's existing forecast models for

the River Irvine and provide revised flood mapping for the Upper Ayr using 1D/2D modelling.

Challenge

Flood forecasting for the River Ayr and Annick Water

Location: Ayrshire, Scotland Client: Scottish Environment Protection Agency (SEPA)

Solution

The forecast system comprises:

- Five gauged lumped Probability Distributed Models (PDMs) for

rainfall runoff modelling

- Six ungauged lumped PDMs and five 1D Flood Modeller (FM) Pro

routing models

- Three hydraulic models and eighteen forecast locations

Benefit

The new flood forecasting and warning system is now operational, and improved flood mapping is available.

Flood warnings can be viewed on the SEPA website. To view the Ayr and Annick Water data expand the "Ayrshire and

Arran" section.

The forecast locations are at key warning areas and at gauging

stations, with error correction at the gauging stations.

We reviewed ratings and developed new ratings, including at the

key gauging stations Dreghorn, Mainholm and Shewalton. We

estimated flood warning thresholds, through the development of

eight new FM hydraulic models.

We carried out end to end testing to ensure consistency of results

between the models and the operational versions on SEPA's

national flood forecasting system FEWS. In addition, we

undertook flood mapping of the upper Ayr using a linked 1D/2D

Flood Modeller/TUFLOW model, to improve upon SEPA's

national flood risk map outputs.

Flow routing from Limmerhaugh

gauging station to Catrine gauging

station on the upper Ayr. Observed =

dashed line. Simulated = solid line

Index