Relation of Coastal Faults and River Morphology to Sea Erosion in Dakshina Kannada, Karnataka

A set of longitudinal and transverse faults have been recognised in the coastal tract of Dakshina Kannada district. The coastal faulting and the uplift of Western Ghats are attributed to sea-floor spreading centred on the Mid-Indian Ridge in the Arabian sea. St. Mary dacite eruption during Late Cretaceous must have heralded sea floor spreading in this part of the West Coast. Variations in the coastline and discrepencies in lithology of coastal Dakshina Kannada are explained by lateral movements along transverse faults. The unusual coast-parallel bends of west flowing rivers appear to be guided by longitudinal coastal faults.

Severe sea erosion in Dakshina Kannada was initiated by the increase of pore water pressure in the coast-parallel river bends and blind tributaries, resulting from massive fluvial discharge during monsoon period. The storm waves may have reactivated preexisting longitudinal faults and triggered slumping of the foreshore sea bed in preferential areas of pore water pressure accumulation and with this, destructive sea erosion commenced and it continued till the stumped area in the foreshore bed was filled up by sands brought back by backwash currents.

It is suggested that severe sea erosion in Dakshina Kannada can be controlled effectively by devising suitable canals to release the surplus stream discharge from the coast-parallel river segments and associated blind streams.