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Byr Brook (Nant Byr)

A stream near Coed-Llai, Flintshire. No gauge of its own: what the river map and the banked data say about it.

Byr Brook (Nant Byr) is a stream on Ordnance Survey’s river map near Coed-Llai, Flintshire, with about 2.0 km of mapped channel. On the map it flows into Afon Alun (River Alyn), which flows on into the River Dee (Afon Dyfrdwy) and out to the sea.

Next gauge downstream

Pont Y Capel River Station on Afon Alun (River Alyn), about 13 km along the river below where Byr Brook (Nant Byr) ends on the map.

0.20 m Normal · steady 30 min ago

After that, Rossett River Station, about 18 km along the river.

No gauge measures Byr Brook (Nant Byr) 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 Byr Brook (Nant Byr)

2 storm overflows are placed on this stream on the river map. Each status is the water company’s own monitor.

Pont Y Bodkin Lower Storm Overflow Monitor offline
Dwr Cymru Welsh Water · into Byr Brook · 2025: 17 spills, 272 h
Pontybodkin Main Storm Overflow Not discharging
Dwr Cymru Welsh Water · into Nant Byr · 2025: 1 spill, 0.8 h

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.

Places along it

From its source towards its mouth, the settlements within a kilometre of it on the map: Coed-talon, Pontybodkin, Coed-Llai, Pontblyddyn.

On the map

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

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

Afon Alun (River Alyn), the river it joins →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 Byr Brook (Nant Byr) 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.
No water-sampling point with a banked sample is placed on this stream. Only England’s samples are banked, and only where the map can place their sampling point.
Nothing on this page says whether any place floods. For an address, see its postcode page.