Now that the weather has calmed down a bit and river levels have fallen, we can consider whether anything of speleological value can be learned from the recent floods.
In the Eastern Valley, resurgences on the east bank from the Castell Coch Limestone continued to show the somewhat anomalous behaviour noticed during very heavy rain last autumn. Whatever reputation this limestone has as an aquifer, it cannot be regarded as a single interconnected system.
The Bouncing Field flooded again on the evening of the 28th February. It is not possible to draw precise conclusions from the relationship between such events and the level of the Afon Llwyd as there are too many uncontrolled variables, including different catchment areas, different flow rates and poorly understood upstream interactions between the surface and underground systems (for instance water passes continually from the beds of the surface river and streams into the underground system at three points at least south of Blaenavon). However the flooding on the 28th was interesting because it took place when the surface river was at a level that has not coincided with flooding of the Bouncing Field in recent years, and a very big extended surge coming down the underground system from north of Blaenavon was not expected (although there had been locally intense rain.). It is clear there is a major constriction in the current main conduit to Pontnewynydd Rising that causes water to back up in the underground system at least as far north as Abersychan. The Bouncing Field does not flood until the water level in the underground system is at least 25m above the level in normal flow conditions. A tentative explanation for the unexpected flooding on the 28th is that the heavy rain from the 8th February onwards had left the storage capacity of the underground system still largely water filled, waiting to get past the constriction north of Pontnewynydd. In other words, in normal conditions there is not just the conduit carrying the "Beyond a Choke" water from Abersychan to Pontnewynydd but also a lot of air filled cave awaiting exploration.
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