Flood hydrological process and its effective control measures in the high-altitude depressions of peak-cluster areas in Lijiang River
With a length of 83 km and an area of about 624 km2,the high-altitude karst depressions in peak-cluster areas are mainly distributed in the middle reaches of the Lijiang River from Daxu town to Yangshuo county,Guilin.There are thousands of depressions in this area,with sufficient nutrients in soil.Large depressions with flat terrain are concentrated with villages,but land resources are scarce.The frequent alternation of droughts and floods has seriously affected not only the local economic development and rural revitalization but also the improvement of landscape resources,which is the main bottleneck restricting the development and protection of natural landscape resources in these depressions.Previous studies mainly focused on the geomorphological origins and geological structures of depressions,but there is little research on the flood formation conditions and hydrological processes.In this study,the Andang depression in the peak-cluster area of Lijiang River basin was selected as a study area in the analysis of flood water cycle,About 3.5 km away from the Lijiang river,the study area is located on the west bank of the Lijiang River,with a catchment area of 2.3 km2.Rainfall mainly recharges the karst underground river channels through A01,A02,A03 and A04 sinkholes in north-south alignment in the central part of the depression,then discharges to the surface at Guanyan village on the west bank of the Lijiang river,and finally flows into the Lijiang River.The elevation of the Andang depression(150 m)is higher than that of the Lijiang river(130 m).A calcite vein about 20 m wide developed in the middle of the depression was mined in the early years.The slag was piled up in Sinkhole A01,resulting in the blockage of underground channels and limited water discharge capacity.Consequently,floods are likely to occur due to the poor drainage system when it rains heavily.With flooding depths of 3-10 m,floods take place 3 or 4 times every year in the depressions,lasting 5-10 days each time,even one month for the longest.A large area of cultivated land in the depression has been deserted due to years of waterlogging.This study established real-time monitoring stations for atmospheric rainfall,surface water level,groundwater level,and outlet flow in the depression to analyze the conditions and causes of floods.The main drainage outlets(A01 and A03 sinkholes)in the depressions were widened and dredged to increase their drainage capacity,which was effective for the control of flood and waterlogging.The results showed that the depression were highly subject to flooding after rainfall.The water depth in the depression could reach the maximum within 12-24 h after the rainfall.If the daily rainfall exceeded 50 mm or the cumulative rainfall exceeded 90 mm in 72 h,the depression was prone to flood.A total of 8 floods occurred in the depression area from April to July,2023,with a flooding time of 417.5 h(18.6 d).The discharge at the outlet of the Yudang underground river reached 77.77%and 87.32%of the rainfall recharge,which was the total groundwater discharge outlet of the Andang depression.The four sinkholes A01,A02,A03 and A04 were discharge outlets for the central section of the underground river.The water discharge rates of these four sinkholes formed four flow peaks at the outlets.Because the hydraulic gradient in Sinkhole A01 was small,and the karst channels of the lower section were blocked by calcite slag,the water discharge speed was slow.Renovating Sinkhole A01 is not an effective way to control flooding in the depressions.Located on the south side of the calcite lode,Sinkhole A03 and Sinkhole A04 were not affected by the blockage of calcite slag;therefore,groundwater discharged smoothly.The dredging of Sinkhole A04 and water diversion from the south of Gucan depression to Sinkhole A03 reduced the flooding time to 66.71 h(2.8 d).Therefore,constructing the south drainage system,diverting water from the south Gucan depression to Sinkhole A03,and discharging water from Sinkhole A04 to the outlet of the Yudang underground river are crucial for further control of flood hazards in the Andang depression.
peak-cluster area in the Lijiang River basinkarst depressionkarst floodhydrological processflood control
万方数据
维普
