by Jim Casey and Oliver Nicholson, OPW, Ireland

Background
The exceptional and in some areas record breaking rainfall that caused some of the worst flooding ever ex-perienced in Ireland began in November 2015 and continued until early January 2016. This weather was punc-tuated by a series of Atlantic Storms, including Storms Desmond, Eva and Frank. Rainfall totals over the peri-od were 189% of normal, making it the wettest winter ever recorded.

The first flood events of this period were witnessed in the north-west on 15 November 2015 and the last flood peaks occurred on 5 January 2016 along the middle and lower Shannon catchment. Flooding was widespread, and the country was in a state of sustained flood emergency for almost two months.

Government Decision
Because of this unprecedented flooding, the Government decided to establish a National Flood Forecasting and Warning Service. Following on from this decision work is proceeding with a first stage implementation of the service that involves the following elements:
•    establishment of a National Flood Forecasting Service as a new operational unit within Met Éireann, Ireland’s National Meteorological Service, and
•    establishment of an independent Oversight Unit within the Office of Public Works (OPW), the lead agency in Ireland for flood risk management.

The service will deal with flood forecasting from fluvial and coastal sources. When established it will involve the issuing of flood forecasts and general alerts. Given the complexities involved in establishing, designing, developing and testing this new service, it is anticipated that the first stage of the service will take at least 5 years before it is operational.

Progressing the Service
The OPW and Met Éireann are working closely together to progress this new service. A Steering Group, including representatives from the OPW, the Department of Housing, Planning, and Local Government, Met Éireann, Department of Agriculture, Food and the Marine, and the Local Authorities has been established to steer, support and oversee the establishment of the new service.

Key progress to date includes:
-    Appointment of initial staff in Met Éireann and OPW to support the management, planning and im-plementation of the new service
-    Appointment of the Chief Hydrometeorologist for the Flood Forecasting Centre in Met Éireann fol-lowing an open competition
-    Preparation and agreement of an implementation plan comprising a number of phases, including an initial set-up phase and a development and trial phase
-    Engagement with national and international experts to explore options for hydrological models and data handling platforms
-    Putting arrangements in place to enhance capacity for interim flood forecasting capability in Met Éireann through appointing two contract hydrometeorological specialists to act in a support role by preparing flood guidance reports, building hydrological expertise and training Met Éireann staff in hydrology
-    Preparation and issuing of a detailed tender brief for hydrological flood forecasting model review, development and trialling (to provide overview and assessment of suitability of models for opera-tional fluvial flood forecasting in Ireland) as outlined in the paragraphs below.
 
Hydrological Flood Forecasting Models - Review Development and Trialling
In tandem with the recruitment of the contract hydrometeorologists, the OPW and Met Éireann collaborated on the preparation of a tender for “the provision of services for the review, development and trial of a range of hydrological models and integrator systems for use in operational fluvial flood forecasting in Ireland” at both catchment and national scales.
 
This contract is expected to commence shortly, and will involve a comprehensive literature review of a num-ber of hydrological models and integrator software systems and shall recommend at least three such hydro-logical models and three integrator software systems considered best suited for the purposes of operational fluvial flood forecasting in Ireland. Following the literature review, each of the recommended hydrological models shall be used to build, calibrate, and validate catchment scale models for five representative catchments in Ireland, including amongst others, the Shannon catchment (see figure).

The examination of available integrator software systems for potential use in conjunction with the operational flood forecasting models will be vital for deciding on how best to facilitate the visualisation of model input and outputs and dissemination of forecast information to relevant stakeholders.

The validated catchment models will then be used in conjunction with the three recommended integrator software systems, to conduct a number of specified forecasting trials.

It is expected that the outcomes of this work (due in late 2019) will be to propose the preferred model(s) to be used for operational fluvial flood forecasting in Ireland and the integrator software that will be used in conjunction with the preferred model(s).