coastal lowland plain of northwestern Morocco. Crossed from east to west by the Sebou River, the Gharb extends about 50 miles (80 km) along the Atlantic coast and reaches some 70 miles (110 km) inland. The lowland, which is bordered by the Rif Mountains (Rif) to the northeast, has gradually been silted up by alluvial deposits from a seasonal watercourse, leaving a surface suitable for agriculture centred on the town of Souq Larb'a al-Gharb (Souk-el-Arba-du-Gharb). It is a major citrus-growing region.