Some articles on watertable:

Coastal Engineering - Construction Techniques - Soft Engineering Methods - Beach Drainage
... Grant (1946) – the elevation of the beach watertable had an important bearing on deposition and erosion across the foreshore ... A high watertable coincided with periods of accelerated beach erosion, and conversely, a low watertable coincided with pronounced aggradation of the foreshore A ... In contrast, a high watertable results in condition favoring beach erosion ...