Agenda item

(1)          Tony Harwood gave a presentation. The accompanying slides are contained within the electronic agenda papers on the KCC website. 

(2)       Mr Harwood said that much of the agenda for the meeting had focussed on the importance of water storage. His role as an Emergency Planner was to ensure effective contingencies in the event of things going wrong. Dams, reservoirs and other water storage facilities being cases in point. 

(3)        Mr Harwood referred to the regulations and guidance in paragraph 1.2 of the report which dictated the parameters within which such documents as the Kent and Medway Offsite Reservoir Inundation Emergency Plan had to be drawn up.  There had been some significant dam failures and disasters both internationally and in the UK; the most well-known example being the Banqiao Dam disaster in China in 1975 where 171,000 people had lost their lives and 11m had been made homeless.   In the UK, 244 people had lost their lives during the Dale Dike Reservoir disaster in Yorkshire in 1874.   More recently, there had been significant dam failures in Laos and North America.  

(4)       Most countries engaged in very detailed contingency planning for dam failures.  In Continental Europe, there were regular emergency drills in those communities that lay down river or in close proximity to dams.   Drills also took place in Asia, North America and Africa.  This contrasted with the UK where emergency planning tended to assume a lower profile. 

(5)       Mr Harwood defined a reservoir as a large raised water body. This meant that it was conceivable that water could ‘fall out’ very quickly.  There were four main types of reservoirs in Kent.  Flood storage areas such as Leigh which could currently hold 5.5m m³ of water, which would expand to 9m m³ once the works there were completed.   Water Utility reservoirs such as Bewl Bridge which could hold 31.4m m³ of water.   Amenity and landscape features such as Mote Park Lake in Maidstone which held some 200k m3 of water.  It was a reservoir that was known technically as a “Cascade” because of its relationship with another upstream reservoir.   Maidstone BC had invested £1.3m on its spillway and dam structure in order to assure its continued safety.  Another designated reservoir (at Leeds Castle) sat above Mote Park Lake, all within the River Len catchment.   

(6)       Mr Harwood moved on to consider the types of reservoir event.   The worst of these would occur as a result of the complete collapse of a dam wall, usually with very little if any warning.  The Emergency Plan needed to set out plans for immediate evacuation in these circumstances and also needed to identify which parts of the transport network would be immediately severed and which parts of the critical infrastructure could be impacted.    

(7)       Another type of event was a slow onset reservoir emergency.  This could arise out of a small leak leading to a gradual loss of water, potentially leading to a riparian fluvial flooding event downstream.   In 2013/14 the flood storage facility on the Shaw Stream in Boughton Monchelsea was filled to the brim and began over-topping.  Such uncontrolled releases could also lead to scouring, where the water would find the point of least resistance, increase the leak and flow out at an ever-increasing rate.    Other types of dam break were “Sunny Day” breaches and “Rainy Day” breaches which gave prominence to the prevailing conditions in which the event occurred.  The former tended to suggest a structural failure whilst the latter suggested that the breach might be the result of increased flows entering the reservoir. 

(8)       Mr Harwood turned to the potential consequences of a reservoir inundation emergency.  These were deaths or injuries to people, damage to property and the residual flooding which was left behind.  To cope with these issues, the Plan had to pre-identify access and egress points as well as muster points for emergency responders.

(9)       Mr Harwood then showed a slide identifying the large raised reservoirs with capacity above 25,000 m³ together with the footprint of where an escape of water would go. It did not state the downstream velocity of any such water loss.   This information was not in the public realm although it did inform Emergency Planning.  The map showed clusters in the Thanet area around “Thanet Earth”, in the Mid Kent area focused on the Greensand Ridge also related to agriculture, the flood storage facilities in the Medway catchment area and the upper parts of the Stour.  

(10)     Mr Harwood said that there was a total of 60 large raised reservoirs which could impact Kent.  44 of these were located within the administrative county of Kent, 6 in the Medway Council area and 10 within neighbouring local authority areas.  The lowest capacity of these large raised reservoirs was 24,400 m³.   Kent had more such reservoirs than other parts of the South East. The number of reservoirs was growing largely because of changes in agriculture systems, with new technologies such as polytunnels and Cravo greenhouses requiring significant irrigation. 

(11)     Mr Harwood concluded his presentation by saying that the Reservoir Inundation Emergency Plan informed the KCC Flood Response Plan and the Local Multi-agency Flood Plans.  An ambitious multi-agency Emergency Planning exercise named Exercise Tethys had taken place in November 2017 to validate the Plan and identify learning points.  Further lessons had been learned from real events that had occurred at the Leigh Barrier and the Parkwood Farm Reservoir at Brishing Dam, Boughton Monchelsea. The Kent Resilience Forum regularly discussed reservoir safety issues. The former Pan Kent Flood Group had been re-named the Pan Kent Severe Weather Group to indicate that it now had the remit to deal with issues around drought and high winds, ensuring that flooding was not treated as an issue on its own.  

(12)     Mr Harwood replied to a question from Mrs Mackonochie by saying that the determination of planning applications for large reservoirs had to take full account of the volume of water contained in a large reservoir as defined by the Reservoirs Act 1975. This included seeking detailed advice from the Environment Agency.  A high level of awareness was also very important when applications came in for fishponds or farm reservoirs to assess the potential for downstream risk. The role of Planning was also significant whenever a development was proposed downstream of an existing reservoir.  Although there were a great number of maps produced by the Environment Agency, the reservoir inundation footprint was not always considered. An example of this had occurred at Turkey Mill close to Mote Park Lake in Maidstone where there had been an application for a pre-school with creche facility, which would have been within the footprint area for a potential dam failure at the Lake. This had been raised by Planners and Elected Members at Maidstone BC leading to the development footprint being moved out of harm’s way, whilst the planning conditions also required identification of muster points and drawing-up of evacuation plans. 

(13)     Mr Tant replied to a question from Mr Howard Rogers by saying that under the terms of the Reservoir Act 1975, the undertaker had to appoint an Inspecting Engineer and a Supervising Engineer in addition to the Design Engineer.   The Design Engineer had to issue a design certificate followed at a later stage by a further certificate that the facility was able to operate properly.  At this point, an on-site plan was developed, followed by an off-site plan. The reservoir had to be inspected every 10 years and it was the undertaker’s responsibility to maintain engineers to inspect it.  It was the Inspecting and Supervising Engineers who had the statutory responsibility to ensure its safety. The Environment Agency had enforcement powers and also ensured that all the required inspections were carried out. 

(14)     Mr Rogers, Mr Tant and Mr Harwood replied to a question from Mrs Bell by explaining that the definition of a reservoir was a water storage facility containing 25,000 m³ of water above ground.  The lowest capacity on the map in the Reservoir Inundation Emergency Plan was 24,400 m³. 

(15)     Mr Rayner asked what regulatory arrangements were in place to deal with landowners who casually created medium sized water storage facilities on their property.  Mr Tant replied that there were a number of regulations in place whose appropriateness depended on the particular circumstances.  For example, a facility that stored water from a water course would require planning consent.  If the landowner was building a reservoir, a Panel Engineer would need to be employed to design it. 

(16)   Mr Harwood said that there had been a number of occasions where water storage facilities had been excavated without planning permission, leading to prolonged periods of enforcement action and retrospective planning applications.

(17)     RESOLVED that the publication of the updated Kent and Medway Offsite Inundation Emergency Plan be noted.