Manor Park has been a problem for years. how about a drainage tank under the tracks and pump the water into Alders Brook.
One has to get the OK from the river authority before pumping into their network. While this sounds reasonable, to stop overloading their own systems, some can take the cheap/easy way out, by not allowing anything.
In dealing with the recurrent flooding in Sodbury Tunnel east of Bristol Parkway on the Badminton line, the river authority refused a whole range of suggestions, eventually saying that the railway should pipe/channel it to the Severn Estuary, which is about 10 miles away.
In passing I would note that at our own house at Canary Wharf, which itself was right in the middle of this Sunday afternoon tempest, in our back garden there was no flooding of the level lawn, it all soaked into the ground. But the progressive concreting over of ever increasing areas means an ever higher proportion of rainfall runs straight off. Meanwhile the gully emptying and periodic maintenance of road drainage seems to have taken ever more of a back seat - the sucker truck I recall regularly around of a generation ago seems to have gone. It's all very well to blame it on global warming, but the solutions (and causes) are often nearer at hand. Divisions of responsibility between local councils, Thames Water, and the Environment Agency, and their internal arguments and buck-passing between one another, doesn't help.