Using an unmanned aerial system to monitor and assess irrigation water channels susceptible to sediment deposition

The irrigation channel of the Qishan River is among the most crucial agricultural water resource facilities in Qishan District, Kaohsiung City, Taiwan. The channel was blocked by debris due to flood events caused by Typhoon Morakot in 2009. This study analyzed images captured by an unmanned aerial system to identify channel areas susceptible to sediment deposition and propose measures for reducing the effects of natural hazards on irrigation water resources. The analysis results revealed that the channel was located downstream of the Qishan River; however, debris flows, riverbank landslides, and natural dam breaches deposited sediment in the downstream section, preventing the flow of water. Furthermore, the sediment and driftwood blocked the channel. The channel was also blocked due to a hyperconcentrated flow. Sediment deposition areas and volumes were estimated. On the basis of these results, we suggest that the damaged riverbed groundsills and river tributary banks be restored to inhibit erosion. In addition, subsurface water collection and transfer structures should be constructed to maintain the flow of water during the dry season. The study findings are expected to increase the efficiency of agricultural irrigation water management and prevent natural hazards from affecting water resources.