Chennai's soil is mostly clay, shale and sandstone.[90] Clay underlies most of the city, chiefly Manali, Kolathur, Maduravoyal, K. K. Nagar, Tambaram, Mudichur, Pallavaram Semmencherry, Alapakkam, Vyasarpadi and Anna Nagar. Sandy areas are found along the river banks and coasts, and include areas such as Tiruvottiyur, George Town, Madhavaram, New Washermanpet, Chepauk, Mylapore, Porur, Adyar, Besant Nagar and Uthandi. In these areas, rainwater runoff percolates quickly through the soil.