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Olchon Brook

A stream near Llanveynoe, County of Herefordshire. No gauge of its own: what the river map and the banked data say about it.

Olchon Brook is a stream on Ordnance Survey’s river map near Llanveynoe, County of Herefordshire, with about 10 km of mapped channel. On the map it flows into Afon Mynwy (River Monnow), which flows on into Afon Gwy (River Wye), then Afon Hafren (River Severn) and out to the sea.

Next gauge downstream

Grosmont Rhosllwyn River Station on Afon Mynwy (River Monnow), about 19 km along the river below where Olchon Brook ends on the map.

0.50 m Normal · steady 15 min ago

After that, Skenfrith River Station, about 29 km along the river.

No gauge measures Olchon Brook itself. A gauge downstream shows water that has already passed it, mixed with everything else that has joined on the way, so it says nothing exact about this stream.

Storm overflows on Olchon Brook

1 storm overflow is placed on this stream on the river map. Each status is the water company’s own monitor.

Longtown Storm Overflow Not discharging
Dwr Cymru Welsh Water · into Unnamed Brook · 2022: 10 spills, 70 h · placed on the river by its position alone

A status says whether an overflow is discharging now, never how much or why. A monitor that is offline or has not reported is not “not discharging”. Sewage in Britain’s rivers →

Live status: © Dŵr Cymru Welsh Water, from its Storm Overflow Map. Annual spill figures: Environment Agency Event Duration Monitoring return, © Environment Agency copyright and/or database right, Open Government Licence (OGL) v3.0.

Water-sampling points on Olchon Brook

2 Environment Agency sampling points are placed on this stream. These are dated samples taken by hand, not live readings, and FloodRadar does not grade them.

Olchon Brook, Longtown Castle
Last sampled 7 Jul 2026 · 3 months ago · 27 samples banked
Olchon Brook upstream of Longtown
No sample published 1 Oct 2023 – 30 Sep 2026

A sample is taken on a date; it says nothing about the water today. A sample below an overflow does not by itself show where anything in it came from.

Water samples: Environment Agency Water Quality Archive, © Environment Agency and/or database right 2026, Open Government Licence v3.0.

Places along it

From its source towards its mouth, the settlements within a kilometre of it on the map: Llanveynoe, Pen-pwll-sond, Clodock.

On the map

The map needs JavaScript. Everything it shows is listed on this page.

The blue line is Olchon Brook; grey lines are other mapped watercourses. Lines from OS Open Rivers (edition 2026-04).

Afon Mynwy (River Monnow), the river it joins →HR2 0NY, a postcode page near where it ends on the map (about 170 m away) →All rivers with gauges →

What this page can and cannot tell you

Its line, its name and where it flows come from Ordnance Survey’s river map (OS Open Rivers, edition 2026-04), which leaves out many small streams, ditches and culverts. “Flows into” is the map’s word: a channel that is not on the map is not shown here, which does not mean it is not there.
No gauge measures Olchon Brook itself, so its own level is not known here.
Storm overflows are listed only where the river map places them on this stream; an overflow it could not place is not counted.
Water samples are England’s only (the Environment Agency’s archive), placed where the map can place their sampling point.
Nothing on this page says whether any place floods. For an address, see its postcode page.