The ground conditions across Brighton shift dramatically between the chalk downland of the South Downs and the coastal plain deposits along the seafront. A site near Preston Park might sit on superficial Coombe deposits overlying chalk, while a plot in the Kemptown area could encounter raised beach shingle and head deposits. These contrasts demand a geophysical approach that can distinguish lithological boundaries without excessive intrusion. The resistivity method maps these transitions by measuring how the subsurface resists electrical current flow. Chalk with flint bands returns a markedly different signature than saturated valley gravels or Clay-with-Flints, and understanding that signature early in the investigation programme saves both time and budget—particularly on constrained urban plots where access for drilling rigs is limited.
The electrical signature of weathered chalk in Brighton—low resistivity over high—reveals the rockhead position without a single borehole being sunk.
