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floodings occurred and which would have been served by the extension of the southwestern
storm relief sewer, the Council decided upon the construction of a short length
of sewer between existing local sewers in Robson-road and Chestnut-road, Norwood,
at an estimated cost of £700.
The Streatham and Balham storm relief sewer was constructed in 1912. It
receives the overflow of the main and local sewers at Tooting Bec-road, and discharges
into the River Graveney at Colliers-wood. An extension which would tap the main
sewer further along its course and increase the usefulness of the sewer was omitted
in 1912. In order to relieve floodings in Balham and to increase the usefulness of the
sewer, the Council decided to proceed with the construction of the extension of the
sewer to Ritherdon-road, a length of about 400 yards, at an estimated cost of £12,000.
The tender, amounting to £10,207 5s. submitted by Mr. Harold E. West, Westminster,
S.W., for the construction of the sewer was accepted on 17th June, 1927.
As a result of further study of the problem of floodings in London, several works
not specifically included in the original scheme were found to be desirable. Two
measures of relief which were relatively small were approved by the Council, and
comprised a diversion of drainage from the Southern outfall sewer No. 2 into the
Southern high-level sewer No. 2, at an estimated cost of £5,000 ; and a diversion of
drainage from the Ravensbourne and Lee-green sewer into the Southern outfall sewer
No. 1, at an estimated cost of £1,000. The former work was rendered desirable owing
to difficulty in dealing with water levels in the Southern outfall sewer No. 2 in storm
times accentuated by the fact that a number of sewers draining higher ground
discharge into the outfall sewer instead of the high-level sewer. The diversion of
drainage from the outfall sewer into the high level sewer will obviate the necessity of
its being pumped at the Southern outfall, and will tend to reduce the surcharging of
the outfall sewer in times of storm. The connection between the Ravensbourne and
Lee-green sewer and the Southern outfall sewer No. 1 is designed to reduce the risk
of flooding in the Coldbath-street area of Greenwich. Both these works are nearing
completion.
For the relief of floodings in the Bow district the gradient of the Eastern Counties
sewer is being improved and re-inverting is also being carried out. The cost of the
work is estimated at £5,000.
A rainstorm of remarkable severity occurred in the afternoon of Monday, 11th
July, 1927. The area most seriously affected was a comparatively narrow strip
extending from Streatham through Hammersmith into Hampstead and Holloway.
Heavy rain began in Balham High-road about 2.45 p.m. and reached Waterlow Park,
Highgate, about 3.50 p.m. and lasted about 2 hours. The maximum recorded fall
was at Hammersmith pumping station, where the total fall measured 2.65 inches.
At places and at periods during the storm, the rainfall was intense. At several places
rain fell at an equivalent rate of 3 inches an hour and over, while at Balham High-road
11 inches of rain fell in 18 minutes, equivalent to the rate of 5 inches an hour. A
rough approximation shows that more than a million tons of water fell in two hours
in the Royal Borough of Kensington and the Metropolitan Boroughs of Hammersmith,
Fulham, Hampstead, and part of Wandsworth. Rainfall of such intensity
is unusual, and there is no record of any fall in London of such intensity for so long
a period. During the storm many sewers were gorged with water, and the street and
other gullies could not pass the water as it fell, and floodings occurred. Storm
relief works comprised in the scheme submitted to the Council on 22nd July, 1919,
which had been completed at an approximate cost of £2,500,000, were in operation,
and large quantities of water were discharged by these means. Otherwise the
floodings would have been much more serious.
The discharge of sewage from Leyton into the London main drainage system,
which was authorised by the London County Council (General Powers) Act, 1925,
commenced on 9th August, 1927.
Streatham
and Balham
storm relief
sewer
extension.
Further
works for
relief of
flooding.
Storm on
11th July,
1927.
Out-county
drainage.