Withernsea lies upon unconsolidated till. This material was deposited by glaciers during the last ice age 18,000 years ago.
The groynes on Withernsea beach ensure wide and relatively steep beaches. The beach material is made up of sand and shingle.
The majority of the Withernsea frontage is provided coastal protection in the form of concrete seawalls and two rock reventments.
The centre section of the Withernsea frontage is provided with coast protection in the form of concrete seawalls and rock armour reventment.
At the north and south ends protection is afforded by concrete reventments.
The whole of the defended frontage benefits from a groyne field which traps sand and has formed wide beaches.
Rock armour has also been placed to the south of Withernsea.