London scoping - ukcip

Final Report
21
Figure 3.8 River Thames flow anomalies at Teddington in winter and summer (naturalised), 1883-
2002. Anomalies are relative to 1961-1990 average.
Winter flow anomaly (cumecs)
200
150
100
50
0
-50
-100
-150
1881 1891 1901 1911 1921 1931 1941 1951 1961 1971 1981 1991 2001
Daily data for Teddington provide an indication of the changing pattern of high flows on the
Thames (defined herein as mean daily flows exceeding 250 cubic metres per second, or
cumecs). Although the last 30-50 years show strong evidence of increases in the number of
high flows, this period is not particularly unusual in the context of the entire record – there have
been flow rich periods in the past, most notably the 1920’s (Figure 3.9). This is consistent with
the national picture of no clear long-term trend in flood peaks, flood volumes or duration of
flood flows (Marsh, 2001a, b; Robson et al., 1998). However, the flows of October to
December 2000 were the most extreme in terms of England and Wales 90-days totals (CEH and
Meteorological Office, 2001). In London two hundred households in Woodford, 75 in
Edmonton and Wanstead were flooded (ABI, 2002). In terms of the maximum recorded mean
daily flows at Teddington since 1900, the snowmelt event of 1947 was the highest on record
(714 cumecs), with the maximum flow of 2000 (464 cumecs) ranked just 50 th . The longest
duration of flows above 250 cumecs occurred in the winter of 1951 following the wettest
February on record (+174% of the 1961-1990 average).