This is a map of the topography of Mid-Somerset in ancient times.
The blue, watery areas were variously open water, marshland or soggy woodland at different times, depending on water levels, which fluctuated throughout history and also seasonally. This area area has, whatever the water levels, always been uninhabitable. Note the old former course of the River Brue, passing by Panborough Hill and into what is now the valley of the River Axe.
Drainage of the wetlands began slowly in the 1600s, progressing more rapidly in the 1800s and completed by the 1940s. But, even today, it is subject to flooding during times of prolonged, heavy rain, and it is also susceptible to possible sea invasion due to rising sea levels or even the possibility of a tsunami originating on the edge of the continental shelf off the coast of southwest Ireland, similar to the deadly tsunami of 1608.
Click on the map for a larger version.