Safe Passage of Riverine Flood from Highly Urbanized City: A Case Study of Lahore City in Pakistan

Unplanned urban spawn in developing countries have resulted in spring of settlements within floodplain of the rivers. Lahore City of Pakistan depicts such an example. In past 100 years, two exceptionally high floods in Ravi River created havoc in the Lahore City, resulting in huge loss of properties and lives. To assess current flood hazards, the researchers analyzed present hydraulic capacity of Ravi River along Lahore City using HEC-RAS software. Digital Elevation Model of 1 m × 1 m, river cross-sectional survey at an interval of 300 m and geometry of structures were used for modeling and analysis of river in HEC-RAS. To safely pass a flood corresponding to 100 years return period, the researchers designed a channel, from Ravi Siphon to Korotana Reserve Forest. Channelization has been proposed in six reaches. Every reach has a unique geometry, based on constraints, presence of bridge, existing settlements or presence of any historic monument. Manning’s equation was used for the design of each reach and analysis was performed on HEC-RAS to verify the hydraulic capacity of the designed channel. Results indicate that the potential consequences of a large flood are disastrous, but the proposed channel can safely pass a flood of 100 years return period, with minimum disturbance to existing infrastructure. The technique used in the research is globally applicable to other sites facing similar problem.