Technical Notes 2021, Issue 98 - Update on Extreme Weather – Friday 6th August to Monday 9th August 2021 – Response from East Dunbartonshire Council & Scottish Water
Section
Extreme rainfall events occurred between the 6th and 9th of August 2021 across parts of the Council area, which put the existing drainage infrastructure across the region under significant pressure. This caused localised flooding across the area, but specifically within certain locations in Bearsden, Bishopbriggs, Kirkintilloch, Lenzie, Milton of Campsie and Milngavie.
The Roads Flood Risk and Drainage Team will receive further information on probability from the Met Office that will allow for further analysis. However, it is believed that these short very intense duration thunder storms are the result of climate change so it is very difficult to predict the future frequency of these events, despite initial reports of a small probability of these occurring every year.
To provide some context, the previous weather event on 9th June 2018 which also caused localised flooding, particularly in the Bearsden and Bishopbriggs areas was noted at the time as a 1 in 500+ year rain storm (very intense). The 2018 event also put the existing drainage infrastructure across the region under significant pressure. At the time the rainfall recorded in some areas was well in excess of normal levels and was measured at the time as a 1 in 500+ year rain storm (very intense) short duration storm which has a 0.05% probability of occurring in every year. Analysis of this year’s event will be undertaken once the information is made available.
It should be noted that the industry standard for the design of a combined sewer system in Scotland is to drain up to a 1:30 year rainfall return period, therefore the rainfall in 2018 exceeded the industry standard design causing localised flooding across the local authority area and the officer expect that the information regarding the most recent event will be similar.
The most recent event was primarily driven by rain
fall causing surface water flooding. In addition, there were some areas where the combined road and waste water system did surcharge causing waste water to remerge from the drainage system. However, early indication shows that much of the surface water flooding was caused by the rainfall being unable to enter the system, as the system was at capacity and the surface water was holding above ground while the system cleared and water within the system dissipated.
Unfortunately there is no immediate solution for this type of flooding as a result of an extreme weather event of this nature. It should be noted that additional gullies do not allow for water to drain quicker when the rainfall is very intense. The Council Flood Risk Officer will continue to explore potential options to address the issues caused by changing rainfall patterns and how some surface water management measures can minimise this type of risk.
As the event was short and intense it took some time for either Scottish Water and/or Council Service to visit all reported locations. It is worth pointing out that the Service has recorded reported flooding incidents at 58 locations with multiple addresses at certain locations.
Responsibility
Scottish Water is responsible for the sewer network which drains both sewage from properties and surface water from roofs and paved areas.
Local Authorities are responsible for draining roads and maintaining road gullies.
Due to the interaction between the road drains and sewer network (combined system) it is important that both the Council and Scottish Water work collaboratively to support those that have been affected. Notwithstanding the statutory responsibilities and recognising the demands being placed upon Scottish Water.
Immediate response to flooding
COUNCIL (Civil Contingences Team - CCT)
In addition to the teams within Roads & Environment, the Council’s Civil Contingencies Team activated initial plans. Officers were in regular contact with other Council services and external partners. Rest Centre preparations were made ready, however did not require to be activated as most residents preferred to stay at home or with family. As with all incidents, the Civil Contingencies team is looking at whether there are any lessons to be learned from a planning and implementation perspective and will review plans and procedures as required.
COUNCIL (Roads)
Flooding to roads should be reported to the Council’s Emergency Response Centre, which passes this information onto the on call Roads Duty Supervisor. The Supervisor will evaluate the requests and take the appropriate action to respond.
This may involve closure of the road to stop traffic driving through flood waters, which can cause waves of flood waters entering gardens and properties.
Due to the weather forecasts received the Roads Standby Team were mobilised in advance of Friday 6th August and had commenced visiting known problematic locations to check and service gullies in advance of the weather front arriving.
Whilst the sole responsibility for protection of private property in the event of a flood lies with individual owners and not the Council or any other Agency, the Council will support the local community, as much as possible, in preparing for and dealing with flood waters with the supply of sandbags. Additional support is also provided, including the provision of bottled water in the event that supplies are affected and the establishment of rest centres to provide secure shelter in the event that evacuations are required.
The Roads Standby Team were also on hand making sandbags available to residents who wished to collect them from Broomhill Depot. Where the team received requests from residents without transport every effort was made to deliver sandbags using the resources available.
During flooding events, particularly out of working hours or during severe events, the roads service will be responding to various locations throughout the council area. As there will be a limited number of resources available even in locations deemed “at risk”, the team cannot provide a guarantee that sandbags will be delivered within a specific timescale and in some cases weather conditions closed in before the team had the opportunity to attend. In the first instance, residents were encouraged to collect sandbags for their own use to allow the Roads resource to be deployed in the field.
The deployment of sandbags is priorities based on the criteria below and the timescale depends on the available resources and operational requirements of the response team:-
- To prevent loss of life or serious injury
- Maintaining access for emergency services
- Protecting vital facilities within the community, i.e. emergency service facilities; publicly owned elderly residential establishments; etc.
- Protection of the Council’s community properties, such as schools and other public buildings, if appropriate
- Protection of Residential Property within the area
- Protection of Business/Commercial property within the area
Future requests for provision of sandbags can be made to the Council, but it is important to highlight that the property owner/occupier is responsible for placing sandbags and undertaking other preventative measures. Sandbags are regarded as a short-term, temporary solution to the problem of flooding. The use of Property Level Protection (PLP) is recommended.
If water enters a resident’s house and they feel that their safety is compromised they can call Scottish Fire and Rescue to assist in evacuation.
There is further advice on SEPA’s floodline website.
The Roads Standby Team were also in communication with the CCT whilst visiting the various flood locations. The team were utilising the information they had to priorities location and take the appropriate action. Where possible the teams were attempting to clear and/or divert flood water to protect residents and property. In addition, as water was surcharging from manholes the covers were being dislodged so the teams were visiting these locations as reports were coming in to mark and replace covers. The RST also organised mechanical sweeping vehicles to attend locations where waste water had emerged on to the carriageway to commence the clean-up operation. It should be noted that the clean-up operations continued beyond Monday 9th August.
COUNCIL (Estates and Facilities Management)
The adverse weather affected a number of schools across the estate. Whilst most water ingress was minor and contained relatively quickly, Bearsden PS, Craigdhu PS and Balmuildy experienced more significant water ingress. A summary of the issues and actions are noted below:
Bearsden PS
The school experienced localised flooding in the Depute Head Teachers office on the first floor which proceeded to enter the reception area directly below on the ground floor. Repairs to ceiling tiles and decoration have been instructed.
Balmuildy PS
There was significant water ingress in the infant area of the school. The area was fully cleaned and ready for school opening on Thursday. The roof at this section of the building is life expired and due for replacement.
Craigdhu PS
Craidghu was the worst affected school in the estate. The roof is currently being replaced therefore the timing of the storm could not have been worse. In addition, the existing outlets on the flat roof are too small and too few to cope with such a significant volume of water. These are being increased in number as part of the roof replacement. The final point to note is that the drainage system in general could not cope with the volume of water during the flooding events, resulting in the water being unable to drain to the system from the rainwater goods. This backed up the system and ultimately led to the roof flooding and the significant water ingress. It should be noted that this was replicated across a number of sites.
In addition to the school estate, the KHCC experienced localised flooding to one stairwell and some adjacent areas. Similar to a number of schools, the drains around the site were unable to cope with the volume of surface water, and as a result the water built up on the flat roof which led to water spilling into the building. Sand bags were provided to site to limit the spread of the water.
FM staff attended all affected sites, mopping up water from the affected areas. Debris has been cleared where required and further cleaning was carried out to ensure the schools were able to open to pupils on Thursday 12th August. Electrics and where applicable fire alarm systems have been checked and confirmed as safe at each location.
Additional Information
SCOTTISH WATER
Any resident or business experiencing flooding by contaminated waste water from sewers should in the first instance call the Scottish Water 24/7 Customer Helpline on 0800 0778 8778 to register the location and issues.
More information can also be found on Scottish Water website.
HOMEOWNERS & BUSINESSES
It should be noted that after the 2018 floods in Bishopbriggs and Bearsden that the Scottish Flood Forum supported the Council to provide Property Level Protection (PLP) surveys for those individual home owners that requested this service.
Unfortunately, neither the Council nor Scottish Water are able to undertake the recommended PLP measures to private property and it would be up to the homeowners as a precautionary approach and additional line of defence from flooding, to research and install any appropriate PLP.
The option of a PLP Survey is still available and any resident or small business affected by the recent flooding that has not used this service can contact the Scottish Flood Forum to make this request.
The Council will also support and encourage local communities and businesses to prepare their own flood risk action plan to deal with emergencies likely to affect them.
SURFACE WATER MANAGEMENT PLANS
The Council continues to develop Surface Water Management Plans for Bearsden, Bishopbriggs and Milngavie in the first planning cycle (2016-2022) under the Flood Risk Management (Scotland) Act 2009 (FRM).
The Council will continue to work with Scottish Water to understand the mechanisms of flooding in the areas affected. The project teams will propose and assess options to improve the management of surface water to minimise flood risk from surface water and sewer infrastructure.
The Council’s Flood Risk Management actions for FRM Planning Cycle 2 (2022-2028) are now available for comment via SEPA’s consultation which closes on the 31st October 2021.
The consultation for the Flood Risk Management Plans and Local Flood Risk Management Plans are now live as is SEPA’s media release.
The Council also has a current consultation online for Climate Ready Park proposal for Etive/Woodhill Park in Bishopbriggs (closes 13th August). This project will help the Council manage surface water management throughout the Bishopbriggs area thus future proofing and minimising flood risk in this catchment.
Any comments can be sent to greenspace@eastdunbarton.gov.uk.
Useful Contacts:
- EDC Contact Centre 0300123510
- Scottish Water 0800 0778778 or contact them via email help@scottishwater.co.uk.
- Scottish Flood Forum can be contacted via email. An independent organisation which supports individuals and communities at risk of flooding and are able to help residents with insurance claims, drying out their home and seeking alternative accommodation. They also advise on appropriate property level protection.