Despite the significance of levees there is less legislation and inspection which makes these structures vulnerable, according to Royal Haskoning DHV group geotechnical director Philip Smith.
Smith made the comments during his presentation at a recent workshop on Seepage Induced Instabilities jointly organised by Imperial College and the University of Sheffield for the British Geotechnical Association and the British Dam Society.
The workshop, which was held at Imperial, was also supported by three technical committees of the International Society for Soil Mechanics and Geotechnical Engineering: TC 105 Geo-Mechanics from Micro to Macro, TC 201 Dikes and Levees, and TC 213 Scour and Erosion.
Smith was speaking at the second workshop event, which focused on considerations around design guidance and codes, and reviewed his experience of levees and flood embankments in the UK. Smith pointed out that these structures are vulnerable as they were typically not designed to particular standards and are often constructed on poor ground; their fragility is typically not apparent.
Considering the performance of embankments in England since 2007, Smith highlighted that the particular threats to UK levees are seepage, internal erosion and uplift; however, with extreme floods such as those in the winter of 2015/2016 overtopping is also an issue.
He noted that these mechanisms pose a greater risk to levees than slope stability failures.
Other speakers at the event included Arup senior engineering geologist Rob Gilbert who describing case histories of dams in Myanmar, Mauritius and Sudan, WJ Groundwater executive chairman Toby Roberts who reviewed some dewatering schemes and Arup fellow Brian Simpson who presented the work of a working group looking at seepage issues related to EC7.
According to event organiser Imperial College professor of particulate soil mechanics Catherine O’Sullivan, one of the repeating themes that emerged from the industry presentations was the need to understand the geology of a site as well as the history of human intervention.
Details of the presentations can be found online here.