"Paul Terry" wrote in message
...
In message , Paul Scott
writes

There are suggestions doing the rounds that this structure wasn't built as
a
water course, but as a 'subway' under Feltham Yard when first built.

No, the subway (in fact there appears to be two) runs parallel with the
river tunnel, as seen he http://www.geograph.org.uk/photo/108858

Right - well done for finding those pictures. I wonder if that more modern
looking ramped access visible in the various aerial view sites, eg Multimap,
just provides an access into the RH of the two smaller tunnels shown he
http://www.geograph.org.uk/photo/366747
to reduce its effective length, ie just to get under the railway?

I wonder if diverting the mill stream caused greater flow in the main
channel, exacerbating the problem?

AIUI the main flow will follow the path of least resistance. I imagine
under the conditions of heaviest rainfall the Crane drains surface run off
from a vast area?

Another possibility is that the smaller tunnels were some sort of flood
channel of course, as originally built.

Paul S