Optimal configuration of a hybrid defense system for hill torrents: an experimental investigation for effective management

Hill torrents originating from higher elevations in mountainous regions can often lead to flooding in downstream cities and areas. The devastating impact of the 2022 Pakistan floods on human activities in the city of Dera Ghazi Khan has underscored the urgency of effective flood management strategies. In this study, experimental investigations were conducted in the laboratory to analyze the energy loss incurred by a hybrid defense system (HDS) designed for hill torrent management. The HDS results were differentiated to a single defense system (SDS) including weir (OW), moat (OM), and vegetation (OV). Parameters such as backwater rise, formation of a hydraulics jump, energy reduction, and the significance of flooding time of arrival have been examined using a total of twelve different hybrid defense system configurations. Both the SDS [–] and HDS [–] experience an increase in water level on the upstream side with the increases in intensity of flood. The experimental results revealed a significant energy reduction of 30% and 50% in the case of the SDS [–] and the HDS [–], respectively. The weir-vegetation-moat configuration demonstrated the highest reduction in the arrival time of floodwater amounting to a 55% decrease compared to other HDS [–] and SDS [–] cases. The obstruction effect observed in the weir-vegetation-moat configuration led to substantial energy reduction, highlighting its potential as a highly effective flood management approach.