37014 - Roding at High Ongar

Grid Reference:	52 (TL) 561 040
Operator:	EA
Local number:	5420
Catchment Area:	95.1 km²
Level of Station:	41.0 mOD
Max. Altitude:	113.0 mOD
Mean flow:	0.48 m³s^-1
95% exceedance (Q95):	0.025 m ³s^-1
10% exceedance (Q10):	1.12 m³s^-1
61-90 Av. Ann. Rainfall:	598 mm

Sample Hydrograph of Gauged Daily Flows

Flow Duration Curve for Gauged Daily Flows

Station Description

'Essex' (modified Flat V) weir in an 11m wide section. Model-based calibration. Overfall operates (>1.7m) into a bypass channel; bypassing can also occur on both banks. Structure subject to drowning (during high flows backwater effects from two d/s bridges are influential); computed flows assume modularity - c/m rating under development; complex history of flood ratings. Evidence of weir settlement discovered in 1991, flows corrected 1987-91. Naturalised flows: 1964-76; minimal net import. Responsive flow regime. Spray irrigation can substantially deplete low flows.

Catchment Description

Generally low lying, largely impermeable (London Clay/glacial deposits), agricultural catchment.

Factors Affecting Runoff

Runoff influenced by groundwater abstraction/recharge.
Runoff reduced by industrial/agricultural abstraction.

River Flow and Catchment Rainfall on the National River Flow Archive

Gauged Daily Flows (gdf):	1963 to 2008
Naturalised Daily Flows (ndf):	1963 to 1975
Naturalised Monthly Flows (nmf):	1963 to 1975
Monthly Catchment Rainfall (rnf):	1963 to 2008

Datatype	1960s										1970s										1980s										1990s										2000s

gdf
ndf
nmf
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.

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