Pis in one of todays papers from a year or two ago,show small trees growing through the part which has now collapsed. Suggests a lack of ongoing maintenance ?
plants growing in expansion joints (a bit like weeds growing in between block paving ) makes little difference when you have massive flows of water under the slipway ,washing out the sub-strait
the slipway is just a small section of the retaining "dam" , i'm sure they will find later that many other sections require beefing up .
I'm surprised the concrete is so thin on the slipway though ,I've seen better shed base pours
as with the other national infrastructures ,like gas and electricity , massive investment is required to the network ,but now the water,gas and electricity is in the hands of the private sector ,shareholder profits are more important than safety or longevity.
I've recently installed a 5 stage filter system on my kitchen tap after seeing the filth that my drinking water filters and Koi pond top up filters captured
that "linescale" in your kettle proves interesting when you test water quality for nitrate,nitrite,PH,lead/heavy metals,chlorine,chloramine, amonia, and tds in general