Located about 20 kilometres south of Alappuzha town, the spillway at Thottappally was built in 1954. Due to southwest monsoon, floodwaters used to accumulate in the rivers of  Kuttanad  making a second crop during autumn impossible. The spillway was constructed to solve this problem by diverting floodwaters directly to the Arabian sea. The National Highway 47 passes over this spillway.