Having got through the Sheffield flood in 2007, which was pretty savage (for Sheffield), it was clear that poor infrastructure and river management were as much to blame as high rainfall. As the city has five significant rivers, with the largest two merging in the city centre, and literally hundreds of streams (and some old colliery soughs) feeding into those, it's always been a water-managed city, not least as the hydro-power systems put in place up to and beyond the industrial revolution demanded control and careful management of the natural supply.
Much of the upstream and downstream sections of the Don, as well as in the centre, have very high walls in place, partly as flood-defence, and partly as control structures to feed water in and out of long-gone mills, dating from the 17th Century up until now. These should have maintained the river integrity even in extreme floods, but the problems were mostly exacerbated by the sheer amount of dead trees, scrap and rubbish washed down from the banks, which then rapidly accumulated under Lady's Bridge and dammed the river, causing it to overflow down the Wicker in minutes. It was like a mini-version of the Japanese tsunamis last year, with the added junk causing more damage, and at least one death.
As most of the river bank upstream is woodland, followed nearer to the city by Victorian factories and other industrial units, it was inevitable that the junk which had accumulated over time would end up in the river. Similarly, many of the streams run underground in culverts, many of which had not been maintained or cleared out for decades. If the banks had been tidy, old trees removed and the walls repaired or renewed, it's arguable that some of the flooding wouldn't have happened, or at least not as catastrophically. But the water levels were huge, with massive saturation underground, and the normally protective sandstone 'aquifer' underlying the city just couldn't hold any more.
Ironically, myself and many other rope-access workers were able to work on huge sections of the flood-defence walls last year, consolidating (or literally rebuilding) the walls, removing problem vegetation, and even working within the culverts, repointing and rebuilding. I pretty much got paid to go 'urban caving' at that stage, which was rather satisfying. But the city, working with the EA and other bodies, is making a huge effort to ensure this never happens again. Luckily, with Sheffield being so hilly, most housing development is above flood levels, but the Don Valley industrial area is the lowest, and so is just as critical from an economic standpoint, even if the risk to personal property/safety is less. However, Catcliffe, near the M1, is very low indeed, and at much higher risk of this sort of event. They are on the flood plain of the Rother, and have flood gates nearby on the river, but as in York, in 2007 the water level was just too much, the gates were raised and the flood plain flooded, as it's meant to. I've often wondered why that settlement exists where it does, as again, it's not all new, but it's obviously a flood plain.