Probably a combination of both. Severe rainfall events are arguably becoming more frequent. More heat in the atmosphere and oceans results in more evaporation=more condensation/cloud=more rainfall. Some argue global dulling is taking place. That combined with more buildings/more impermeable surfaces=greater storm run off and less space for the runoff causes greater depth of flooding. Therefore the likelihood of more Boscastle-type events increases and not just in UK. Essen down to Cologne took a pasting today. Let's hope it's dry on August 5th.