The National River Flow Archive

38022 - Pymmes Brook at Edmonton Silver Street

Grid Reference:	51 (TQ) 340 925
Operator:	EA
Local number:	5369
Catchment Area:	42.6 km2
Level of Station:	11.1 mOD
Max. Altitude:	107.0 mOD
Mean flow:	0.48 m3s-1
95% exceedance (Q95):	0.11 m3s-1
10% exceedance (Q10):	0.99 m3s-1
61-90 Av. Ann. Rainfall:	671 mm

Sample Hydrograph of Gauged Daily Flows

Flow Duration Curve for Gauged Daily Flows

Station Description

Crump weir (width: 6.16m) in concrete channel, installed in 1972; superseded a rated trapezoidal section, data from 1954 (rating change in 1963; series reprocessed). Few confirmatory gaugings at high flows. Rarely overtopped. Drowns regularly (c0.7m stage) - flows corrected since 1982; previous high flows under review. Pre-1965 runoff substantially enhanced by sewage effluent (now treated outside catchment). Currently no significant abstractions or discharges.

Catchment Description

Impervious (London Clay) catchment. Pymmes Brook rises on Enfield Chase but catchment is now approx. 60% urban.

Factors Affecting Runoff

• Natural to within 10% at the 95 percentile flow.

River Flow and Catchment Rainfall on the National River Flow Archive

Gauged Daily Flows (gdf):	1954 to 2006
Monthly Catchment Rainfall (rnf):	1961 to 2006

Datatype	1950s										1960s										1970s										1980s										1990s										2000s
gdf
rnf

For many stations monthly peak flows are also archived. When daily flow data are not available monthly mean flows may be held on the National River Flow Archive. See Data Holdings for further information.

NRFA Home Page
    Station Summaries
    Regional Maps
    Data Holdings

http://www.nerc-wallingford.ac.uk/ih/nrfa/station_summaries/038/022.html