 Additionally, the high speed at which abundant surface runoff runs down the valley's slopes poses a big risk for nearby populations.Most of the floods in the Valley can be explained due to the difference in altitude and the inability of the sewerage system to pump the water out during the monsoon season.The Great Canal has lost its gradient due to land subsidence in some parts of the city, losing its discharge capacity from 90 m³/second to 12 m³/second in the last 30 years, and the secondary sewerage network is insufficient to carry high volumes of stormwater and wastewater.