黄河于150 ka BP切穿三门峡,东流入海.黄河泥沙90%来自黄土高原.黄土高原土地利用和植被的变化对黄河输沙有决定性的影响.15万年以来,黄河进入华北平原的泥沙约70 000×108 t,其中10 ka BP以前占80%.10 ka BP以后的输沙量中,最后104...黄河于150 ka BP切穿三门峡,东流入海.黄河泥沙90%来自黄土高原.黄土高原土地利用和植被的变化对黄河输沙有决定性的影响.15万年以来,黄河进入华北平原的泥沙约70 000×108 t,其中10 ka BP以前占80%.10 ka BP以后的输沙量中,最后1040年黄土高原滥垦时期占60%.黄河泥沙的归宿,建造华北大平原占73%,流入海洋占26%.现在,黄河每年流入北黄海的泥沙不足0.2×108 t,其输运主要受海洋环流系统的影响.现在黄海每年向东海输运悬浮沉积物0.2×108～0.3×108 t,主要为废黄河三角洲及水下三角洲受侵蚀再悬浮的黄河泥沙.1996-2000年黄河下游连年断流,利津站的年径流量和输沙量只有1950-1979年30年平均的19%左右.今后20～30年内,由于气候变暖、工业、城市等引黄水量增加,黄河的入海泥沙量仍将偏少.展开更多
The Yellow River cut through Sanmenxia Gorge and discharged into the sea via the North China Plain in 150 ka BP; since then, around 86 000 × 108 t sediment has been transported passing Sanmenxia Gorge. Based on l...The Yellow River cut through Sanmenxia Gorge and discharged into the sea via the North China Plain in 150 ka BP; since then, around 86 000 × 108 t sediment has been transported passing Sanmenxia Gorge. Based on land use and land cover changes in Loess Plateau and other available evidence, an estimate of the Yellow River sediment budget is presented here： about 72% of the sedimentary material was trapped in the North China Plain and the remainder（i.e., 26%） escaped to the sea. At the present stage, 〈 0.2×108 t/a suspended sediment of the Yellow River enter the northern Yellow Sea. The transport pattern is determined mainly by the shelf current system. Annually 0.2×108–0.3×108 t of suspended particles are carried to the East China Sea; the materials are derived mainly from coastal and subaqueous delta erosion associated with the abandoned Yellow River on the Jiangsu coast. Since 1972, the lower Yellow River started to have a situation of continuous no-flow. During 1996–2000, the annual water flow and sediment discharge are only 19%, as compared with normal years（i.e., average for 1950–1979）. In response to global warming and increase of water diversion from the Yellow River for industrial and urban use, the sediment flux of the Yellow River to the sea will most likely remain small in the next two to three decades.展开更多
Efforts to restore urban rivers require an understanding of human-influenced changes in channel substrates. This study uses three naturally-occurring oxbows in a 3.5 km reach of Swan Creek, flowing through the City of...Efforts to restore urban rivers require an understanding of human-influenced changes in channel substrates. This study uses three naturally-occurring oxbows in a 3.5 km reach of Swan Creek, flowing through the City of Toledo, Ohio (USA) to reconstruct historical changes in channel substrate. Human impacts in the watershed were: 1) land clearance for agriculture (peaking in 1900-1920) and for suburban housing tracts (peaking in 1945-1970), followed by 2) the post-1940 creation of more efficient urban run-off systems from streets, parking lots, housing developments, and shopping centers. Historical aerial photographs and maps from 1935, 1940, 1950, 1963, 1974, and 1994 were georeferenced using ground control points, input to ArcGIS, and have root mean square error (RMSE) ranging from 0.19 - 0.77 m (average RMSE = 0.47 ± 0.20 m) when compared to the 2006 digital ortho quarter-quadrangle (DOQQ) image used as the basis for comparison. Results showed that channel sinuosity continually increased from 1.88 (1935) to 1.99 (2006). Two oxbows probably formed in 1913, and the third formed in 1940. Sediment cores and trenches were used to recognize historical channel substrates. Age control was provided by <sup>14</sup>C geochronology and labels on food packaging materials found in flood layers. Grain-size analysis of channel substrates shows a historical coarsening-upward trend: the largest clast size interval (f<sub>5</sub>) changes from +0.78f in pre-1935 channels, to -1.15f in pre-1940 channels, to -1.69f in the 2006 channel. These results indicate recent urban runoff created fluvial pavements and increasing channel mobility as the stream removes legacy sediment from intrabasinal sediment storage.展开更多
The Wenchuan Earthquake caused a large number of avalanches and landslides at different scales. It is extremely significant to evaluate the sediment in the earthquake river basins. Along the 38 km long upper Mianyuan ...The Wenchuan Earthquake caused a large number of avalanches and landslides at different scales. It is extremely significant to evaluate the sediment in the earthquake river basins. Along the 38 km long upper Mianyuan River 196 landslides and avalanches happened during the earthquake, which have formed 25 landslide dams and quake lakes. The total volume of sediment erosion due to earthquake was about 115 million m3, which is 75 times higher than the soil erosion in normal years. Only a part of the solid material could be transported by the river water flow as suspended load and bed load. The total volume of bed load deposit in the river and the quake lakes was 1.43 million m3. Moreover the quake lakes had also trapped 0.12 million m3 suspended load. Only 0.18 million m3 of fine sediment had been drifted through the quake lakes and transported into the lower reaches of the Mianyuan River. The wide range of size distributions of sediment from earthquake erosion caused the extreme difference in the amounts of sediment erosion and transportation. Most of the sediment from earthquake erosion can be only transported for a short distance by landslides and debris flows. Less than 0.2% of the total volume of sediment from earthquake erosion may be transported into large rivers. Therefore, earthquake erosion has little effect on the sediment transportation and fluvial processes in the large rivers.展开更多
文摘黄河于150 ka BP切穿三门峡,东流入海.黄河泥沙90%来自黄土高原.黄土高原土地利用和植被的变化对黄河输沙有决定性的影响.15万年以来,黄河进入华北平原的泥沙约70 000×108 t,其中10 ka BP以前占80%.10 ka BP以后的输沙量中,最后1040年黄土高原滥垦时期占60%.黄河泥沙的归宿,建造华北大平原占73%,流入海洋占26%.现在,黄河每年流入北黄海的泥沙不足0.2×108 t,其输运主要受海洋环流系统的影响.现在黄海每年向东海输运悬浮沉积物0.2×108～0.3×108 t,主要为废黄河三角洲及水下三角洲受侵蚀再悬浮的黄河泥沙.1996-2000年黄河下游连年断流,利津站的年径流量和输沙量只有1950-1979年30年平均的19%左右.今后20～30年内,由于气候变暖、工业、城市等引黄水量增加,黄河的入海泥沙量仍将偏少.
文摘The Yellow River cut through Sanmenxia Gorge and discharged into the sea via the North China Plain in 150 ka BP; since then, around 86 000 × 108 t sediment has been transported passing Sanmenxia Gorge. Based on land use and land cover changes in Loess Plateau and other available evidence, an estimate of the Yellow River sediment budget is presented here： about 72% of the sedimentary material was trapped in the North China Plain and the remainder（i.e., 26%） escaped to the sea. At the present stage, 〈 0.2×108 t/a suspended sediment of the Yellow River enter the northern Yellow Sea. The transport pattern is determined mainly by the shelf current system. Annually 0.2×108–0.3×108 t of suspended particles are carried to the East China Sea; the materials are derived mainly from coastal and subaqueous delta erosion associated with the abandoned Yellow River on the Jiangsu coast. Since 1972, the lower Yellow River started to have a situation of continuous no-flow. During 1996–2000, the annual water flow and sediment discharge are only 19%, as compared with normal years（i.e., average for 1950–1979）. In response to global warming and increase of water diversion from the Yellow River for industrial and urban use, the sediment flux of the Yellow River to the sea will most likely remain small in the next two to three decades.
文摘Efforts to restore urban rivers require an understanding of human-influenced changes in channel substrates. This study uses three naturally-occurring oxbows in a 3.5 km reach of Swan Creek, flowing through the City of Toledo, Ohio (USA) to reconstruct historical changes in channel substrate. Human impacts in the watershed were: 1) land clearance for agriculture (peaking in 1900-1920) and for suburban housing tracts (peaking in 1945-1970), followed by 2) the post-1940 creation of more efficient urban run-off systems from streets, parking lots, housing developments, and shopping centers. Historical aerial photographs and maps from 1935, 1940, 1950, 1963, 1974, and 1994 were georeferenced using ground control points, input to ArcGIS, and have root mean square error (RMSE) ranging from 0.19 - 0.77 m (average RMSE = 0.47 ± 0.20 m) when compared to the 2006 digital ortho quarter-quadrangle (DOQQ) image used as the basis for comparison. Results showed that channel sinuosity continually increased from 1.88 (1935) to 1.99 (2006). Two oxbows probably formed in 1913, and the third formed in 1940. Sediment cores and trenches were used to recognize historical channel substrates. Age control was provided by <sup>14</sup>C geochronology and labels on food packaging materials found in flood layers. Grain-size analysis of channel substrates shows a historical coarsening-upward trend: the largest clast size interval (f<sub>5</sub>) changes from +0.78f in pre-1935 channels, to -1.15f in pre-1940 channels, to -1.69f in the 2006 channel. These results indicate recent urban runoff created fluvial pavements and increasing channel mobility as the stream removes legacy sediment from intrabasinal sediment storage.
文摘The Wenchuan Earthquake caused a large number of avalanches and landslides at different scales. It is extremely significant to evaluate the sediment in the earthquake river basins. Along the 38 km long upper Mianyuan River 196 landslides and avalanches happened during the earthquake, which have formed 25 landslide dams and quake lakes. The total volume of sediment erosion due to earthquake was about 115 million m3, which is 75 times higher than the soil erosion in normal years. Only a part of the solid material could be transported by the river water flow as suspended load and bed load. The total volume of bed load deposit in the river and the quake lakes was 1.43 million m3. Moreover the quake lakes had also trapped 0.12 million m3 suspended load. Only 0.18 million m3 of fine sediment had been drifted through the quake lakes and transported into the lower reaches of the Mianyuan River. The wide range of size distributions of sediment from earthquake erosion caused the extreme difference in the amounts of sediment erosion and transportation. Most of the sediment from earthquake erosion can be only transported for a short distance by landslides and debris flows. Less than 0.2% of the total volume of sediment from earthquake erosion may be transported into large rivers. Therefore, earthquake erosion has little effect on the sediment transportation and fluvial processes in the large rivers.
