Smart Flood Management
With climate change and rising sea levels the UK needs robust flood management plans. According to The Royal Institute of British Architects 1.5 per cent of the UK is at risk from direct flooding from the sea and about 7 per cent of the country is likely to flood at least once a century from rivers. The cost to the UK is around £2.2 billion (Somerset County Council claimed around £2 million in government support and the cost of repairing Wales’ coastal defences, roads, railways is expected to be over £25 million), but less than £1 billion is spent on flood protection and management.
When it comes to natural events, money is only part of the solution, being prepared is the key. Recognising that there is a finite pot of money available to address flood protection measures means smart thinking by Local Authorities. For example, given the necessary information, surveyors are able to focus on high-risk drainage systems that are in populated areas and give lower priority to gullies that are away from habitation and businesses and are, therefore, much less likely to pose a risk.
Fortunately there is a wealth of data available to help Local Authorities make more informed decisions for targetting resources at flooding hot spots. Systems that provide visualised asset management, such as Yotta’s Horizons, are making it easier to use the information by bringing together various and valuable data sets to build a multidimensional view of flood risk and this enables informed reactive maintenance and better planning.
Gulley silt level and condition surveys provide important data; Wigan Council is an example. Yotta performed the first of three gulley surveys across 1040 km of the council’s highway network last October collecting detailed data for 58,000 gullies. The survey data provide silt depth trends over several years. The information collected quickly helps to highlight whether the gulley cleaning regimes are sufficiently robust or need altering to suit specific roads.
Cross referencing the data to a geographic information system (GIS) opens up other possibilities such as helping the Authority’s call centre to deal with enquiries and reports from the public. Other measures such as mobilising the GIS enables maintenance teams to update it in real-time as they go about their gulley cleaning operations. Such mobile systems can also incorporate real-time automatic data feeds from satellite vehicle tracking technology when fitted to gulley cleaning and street-sweeping equipment.
Vehicle-based digital video inventory surveys that include gulley asset information provide a clear and accurate view of an Authority’s drainage systems. Here, the gullies are photographed in high resolution and mapped digitally with their precise locations confirmed by GPS. Again, importing the data into a GIS enables highways engineers to construct flood models showing problem gullies, their precise location and flooding potential.
Flood data and maps, data sets and imagery provided by aerial photography services also play their part in helping flood risk management. For example Bluesky’s National Tree Map data with geotagged LiDAR (light detection and ranging) terrain imagery can help locate and assess where leaf fall could block gullies. Also, by mapping the height of gullies and measuring gradients, LiDAR helps assess the capability of drainage systems to cope with heavy rain and flash floods.
But, it’s not all about cleaning gullies and other manmade systems. Local Authorities can use available data to help plan sustainable drainage systems (SuDS) to alleviate flooding. Surrey Heath Borough Council, for example, uses LiDAR data from Bluesky to help flood alleviation works on Chobham Common. Aircraft-mounted sensors captured the land elevation data and these are used to model the flow of water across the heathland. Using this information, the Council has identified the potential to reinstate some medieval ponds and hopes to attenuate flood water running off the common into nearby villages.
Elsewhere 360 degree video surveying from SphereVision is being used to record actual flooding using a portable system that can be fitted to boats, vehicles or simply carried. The video record can be used for future infrastructure and emergency planning to help prevent – or better deal with – future disasters. This enables local authorities to predict the actual impact of subsequent flooding based on historic real images rather than rely on computer simulations and predictions, which could miss factors such as the added impact of local flash flooding surface water run-off. Additionally, such surveys can be used to record and visualise potential flood areas beyond road networks, such as adjacent flood plains and other areas used for SuDS.
Written by: Iestyn Armstrong-Smith, Freelance technology writer.