On flood plains.Do you get house insurance?
Hope you are not in that area @Phil ??
There is very tight legislation and registration about dams above quite a small storage capacity which becomes even more stringent if failure would present a significant loss of life as in this case.The problem is that our dams here in the Peak District ( and I suppose most others) were built by the Victorians nearly 200 years ago and are mainly composed of earth and stones and clad with pretty looking pieces of masonry. They start off many metres thick and taper until they just a couple at the top. very little investment has been made other than plugging the odd leak, so this was bound to happen, and as long as we keep building on flood plains it is going to get worse. Our town, amongst other, was badly flooded a few years ago, so they improved our flood defences. How? By scraping out the river and brook and lining then with stone setts, so now the water flows rapidly straight through and on to the next poor souls down stream. I agree that things have in recent years got more difficult, but in many cases we are the creators of our misfortune as far as the flooding goes
And remember that this a canal reservoir at the start of the Peak canalThere is very tight legislation and registration about dams above quite a small storage capacity which becomes even more stringent if failure would present a significant loss of life as in this case.
Therefore to suggest a lack of maintenance without evidence is unfair.
There will have been regular inspections and recertification by a specialist engineer.
However an earth same is only as good as the waterproofing skins front and back so when an extraordinary overflow manages to disturb the spillway and get underneath it the danger of further erosion and collapse is very significant.
It will be interesting to hear in due course whether the seal between the slabs in the spillway were inspected and maintained.
Gorilla Glue seems to be the "go To" stuff these days.Mastic and gaffer tape should hold.