Pluvial (Rain) – if it rains heavily then, due to rapid run-off from built environment, clogged gullies etc.roads, car parks and local areas can flood, especially if drain capacity is exceeded.
Fluvial (River or stream) – the brook could burst its banks – likely due to heavy rain in the upper catchment which is heavily built up, so surface water runs off rapidly making the brook ‘flashy’
Groundwater – there are some areas where, especially in winter, the ground becomes waterlogged leaving little capacity to absorb more water. This is notable south of the railway tracks.
Tidal – currently the combination of Thames Barrier and height of river wall provides significant protection, but if either should fail then large areas of Barnes, Mortlake, Hammersmith, Chiswick and other parts of London would liable to be flooded. Most of Barnes lies within this potential flood zone, and lower parts such as near the Terrace would be in a ‘rapid inundation zone’. Some houses in these areas still have older generations of flood defences protecting individual properties.
Tidal Lock – if significant rainfall coincides with high tide then the water cannot drain away to the Thames. Water will build up behind the tidal defences (non-return valves) and/or rising water in tidal reaches and, if the capacity available is not enough, then flooding occurs (as in July 2021).
Most significant flooding in recent years in Barnes has been ‘local’ street flooding for various reasons, including blocked drains or gullies, water leaks etc, but some streets in low lying areas are prone to tidal lock.