Agenda item

Martin Holland, Head of Highways and Energy Services gave a presentation on Flood Preparedness.

In the presentation and discussion the following points were made:

·         In drainage terms, Islington was part of the Thames Basin. The origins of the basin went back to the ice age and the consequences had shaped today’s drainage arrangements. As the ice sheets receded, meltwater flowed away carrying silts and gravels. What was now the Thames had its origins across the Midlands and had continued to move south to its present position. As the meltwater moved south it created terraces of gravels that allowed springs and wells to develop, such as the Sadlers Wells at Spa Green.

·         These springs became the source of streams.

·         Such watercourses provided the main discharge for surface water – eventually flowing into the Thames.

·         As rural Islington developed, the water course was canalised and fed by ditches and dykes.

·         As urban Islington spread, the watercourse had its banks built up until they were piped and now form Thames Water’s main storm drains.

·         As Storm Culverts replaced the rivers they become combined sewers, taking sewage and surface water.

·         All main drainage is the responsibility of Thames Water.

·         Other than domestic estate drainage, Islington was only responsible for surface water from the gullies in its streets down to the sewer.

·         Any surcharging of the combined sewers would result in flooding by contaminated sewage.

·         The Flood and Water Management Act (FWMA) and the Flood Risk Regulations 2009 (FRR) placed a duty upon the London Boroughs to act as the Lead Local Flood Authorities (LLFA). Having carried out initial assessments Islington must now produce a Local Flood Risk Management Strategy (LFRMS).

·         Local Strategies for Flood Risk Management had to be consistent with the Environment Agency’s National Strategy. A local strategy must cover local flood risk, which was likely to include the 1) surface water flooding; 2) groundwater flooding and 3) flooding from smaller rivers.

·         LLFAs were responsible for developing and applying their local strategy and other risk management authorities must act consistently with the local strategy.

·         The other partners in delivering the local strategy would include: 1) the Environment Agency; 2) neighbouring authorities; 3) Thames Water and 4) Transport for London (as a Highways Authority).

·         The Local Strategy must contain: 1) the risk management authorities in the authority’s area; 2) the flood and coastal erosion risk management functions that may be exercised by those authorities in relation to the area; 3) the objectives for managing local flood risk; 4) the measures proposed to achieve those objectives; 5) how and when the measures were expected to be implemented; 6) the costs and benefits of those measures and how they were to be paid for; 7) the assessment of local flood risk for the purpose of the strategy; 8) how and when the strategy was to be reviewed and 9) how the strategy contributed to the achievement of wider environmental objectives.

·         The strategy would be produced in conjunction with inputs from council officers (through workshops at the council offices and input through the development of the draft local strategy), representatives from risk management authorities and local stakeholders i.e. the Environment Agency, Thames Water, neighbouring LLFAs, Network Rail, Transport for London, the London Fire Brigade and residents, businesses and other stakeholders through formal consultations.

·         The council had commissioned consultants to provide the strategy. The draft would be circulated in the next few weeks and subject to Executive member approval would be released for public consultation in early 2017.

·         Additional modelling could be required for specific areas of the borough.

·         There was very little history of surface water flooding in Islington.

·         Initial assessments showed that the routes of the old rivers had a higher probability of flooding along with hilly areas where there were velocity surcharges.

·         Former marshes like Tufnell Park did suffer from flooding during the 1950s but this was rectified by the construction of new storm culverts and the installation of anti-flood valves on the drainage outlets. However, the significant flooding events in Islington had been the result of burst water mains.

·         The events that had historically caused flooding in Islington were not covered by the regulations which stated that a flood did not include a) a flood from any part of a sewerage system, unless wholly or partly caused by an increase in the volume of rainwater (including snow and other precipitation) entering or otherwise affecting the system, or b) a flood caused by a burst water main.

·         Going forward the council would be involved with 1) preparing and maintaining a strategy for local flood risk management; 2) maintaining a register of assets vulnerable to flooding; 3) investigating significant local flooding incidents and publishing the results of such investigations; 4) establishing approval bodies for design, building and operation of Sustainable Drainage Systems (SuDS); 5) issuing consents for altering, removing or replacing certain structures or features on ordinary watercourses; 6) playing a lead role in emergency planning and recovery after a flood event.

·         The officer confirmed that the local authority could do little to prevent subsidence other than by keeping the drainage efficient.

·         The council now had a basement policy. Basements were at a greater risk of flooding.

·         The council worked closely with utility companies. If a pipe burst, it was their responsibility. If there was a flash flood, Islington’s drainage should be able to cope to a certain extent. However water could build up if the drains the water fed into could not take the water away quickly enough.

·         Street Environment Services emptied gullies. If it was not possible to clear a particular drain, Highways would be contacted and a camera would be put into the drain to investigate the problem. If it was caused by a Thames Water drain problem, they would be asked to clear the drain.

·         Thames Water were carrying out Victorian water main replacement and had reduced the water pressure to try and stop leaks. Water now had to be pumped to the top of tower blocks due to the pressure reduction.

·         The areas in Islington most likely to flood were the Gospel Oak to Barking Line, the North London Line, the tube line and the canal. Finsbury Park station was also at risk. The London Underground managed the Finsbury Park flood risk.

·         In Sustainable Drainage Systems (SuDS) water would either be contained, went into gardens or into culverts from which it would be released once the drains had capacity.

·         In response to a question from a member of the public as to why when the council had been funded since 2011 to produce the local strategy had it taken until now to produce, the officer advised that this had not been prioritised by the council. However the council had done work to collate and understand how the drainage worked. The strategy would be published by 2017 in line with the requirements.

·         In response to a question from a member of the public about how the council was working with partners and other local authorities, the officer advised that the council worked with Drain London which led a partnership of London boroughs and other partners. Meetings were held every nine months.

·         In response to a question from a member of the public about the risk from reservoirs in Hackney, the officer advised that the two reservoirs in the north had been drained and were empty, the one in Dartmouth Park Hill had been reduced and the officer was unclear whether the one at Pentonville Road at Amwell Road was still in use but enquiries could be made with TfL and the information published.

·         In response to a question from a member of the public, the officer stated that although no climate change modelling had been undertaken by the council, it had been undertaken by others.

·         The officer confirmed that there was currently information on the website about the council’s flood preparedness.

RESOLVED:

That the presentation be noted.