Flooding visualisations

Mott MacDonald were comissioned to simulate storm events in Hirael Bay to compare the effectiveness of the different defence options that are being considered. The key at the bottom right of each simulation shows how deep the water is during various stages of the storm event. For a full explanation of the animations, please click below…

Walkaway scenario: 2055 sea level

This flood animation shows the flood extent and water depth caused by a 1 in 50 year (2% chance of occuring in a single year), 8-hour long storm event if there were no defences in place in 2055, and if the current promenade was left unmaintained.

In this scenario, the existing coastal frontage is overtopped and enters Hirael via Beach Road east car park, and crosses Beach Rd and travels up Llys Emyrs. Water St, Orme Rd, Seiriol Rd and Glandwr Rd are also indundared in this scenario.

Walkaway scenario: 2020 sea level

Defences in place scenario: 2055 sea level

This flood animation shows the flood extent and water depth caused by a 1 in 50 year, 8-hour long storm event in 2055 if a 6.66m (sea level to wall crest) defence was constructed. 

A proposed new flood defence consists of flood walls along the coastal frontage and flood gates at Glandwr Road and Beach Road West Car Park. The average height of the proposed defences is 1.4m along the promenade.

Although some flooding does occur on Water St and Llys Emyrs, the water depth is negligable and would not flood any properties.

Defences in place scenario: 2020 sea level

This flood animation shows the flood extent and water depth caused by a 1 in 50 year, 8-hour long storm event in 2055 if a 6.66m (sea level to wall crest) defence was constructed. 

A proposed new flood defence consists of flood walls along the coastal frontage and flood gates at Glandwr Road and Beach Road West Car Park. The average height of the proposed defences is 1.4m along the promenade.

Flood defefences provide a significant level of protection in this scenario, with only minor overtoppings of the wall which are constrained to the promnade.

Shorter defences in place scenario: 2055 sea level

This flood animation shows the flood extent and water depth caused by a 1 in 50 year, 8-hour long storm event in 2055 if a 6.33m (sea level to wall crest) defence was constructed.

This option sacrifices a small amount of wall height in favour of a slightly improved view of Hirael bay, at the cost of more flooding. The water which does enter Hirael is not very deep, however it is noticably more widespread.

This simulation highlights the importance of constructing adequately high defences to future-proof the scheme.

 

 

 

 

3D Model of the proposal

Hirael flood prevention scheme

FCRMU@gwynedd.llyw.cymru

YGC | Ymgynghoriaeth Gwynedd Consultancy

 

Shirehall Street

 

Caernarfon

 

Gwynedd

 

LL55 1SH