CONTROLLING the YELLOW RIVER 2000 Years of Debate On
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Technical Secretariat for the International Sediment Initiative IHP, UNESCO January 2019 Published by the United Nations Educational, Scientific and Cultural Organization (UNESCO), 7, place de Fontenoy, 75352 Paris 07 SP, France, © 2019 by UNESCO This publication is available in Open Access under the Attribution-ShareAlike 3.0 IGO (CC-BY-SA 3.0 IGO) license (http://creativecommons.org/licenses/by-sa/3.0/igo/). By using the content of this publication, the users accept to be bound by the terms of use of the UNESCO Open Access Repository (http://www.unesco.org/open-access/ terms-useccbysa-en). The present license applies exclusively to the text content of the publication. For the use of any material not clearly identified as belonging to UNESCO, prior permission shall be requested. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of UNESCO. ©UNESCO 2019 DESIGN, LAYOUT & ILLUSTRATIONS: Ana Cuna ABSTRACT Throughout the history of China, the Yellow was the major strategy of flood control. Two River has been associated with frequent flood extremely different strategies were proposed and disasters and changes in the course of its lower practiced in the past 2000 years, i.e. the wide river reaches. The river carries sediment produced and depositing sediment strategy and the narrow by soil erosion from the Loess Plateau and the river and scouring sediment strategy. Wang Jing Qinghai-Tibet plateau and deposits the sediment implemented a large-scale river training project on the channel bed and in the estuary. The in 69 A.D.. He completed and enhanced the erosion rate accelerated in the past 2000 years levees and built many diversion channels and due to climate change. The sedimentation rate weirs. He constructed many gates about 5 km increased from 1-3 mm per year to 30 mm per apart on the grand levees. The river was confined year from 00 A.D. to 1855, mainly due to human by the enhanced levees tens of kilometers apart, activities. From 1855-1985 human activities giving enough space for sediment deposition. greatly accelerated the sedimentation and the The riverbed silted up at a low speed of less than sedimentation rate rose to 50-100 mm per year. 1-cm per year. During great events, water and Over time, a perched river formed that frequently sediment were diverted through the water gates breached its levees. From 602 B.C. to 1949 the into diversion basins. In the following 800 years river experienced 1,593 levee bursts, flooding the river was tamed and no big flood disasters vast areas, in 543 years and claiming millions of occurred. human lives. The river shifted its main course (600-700 km long) by avulsion 26 times with the From 850 A.D. to 1500 A.D. the river woke again apex around Zhengzhou, resulting in devastating and became very active. Sedimentation on the calamities and numerous old channels, including riverbed resulted in high flood stages approaching 8 major shifts (5 natural and 3 human-caused) the crest of the grand levee. The Grand Levee with the river mouth alternating between the was breached once per 2 years during the period. Bohai Sea and the Yellow Sea. Because of its wild Closing the breached levee was a hard job for behavior, the lower Yellow River was dubbed “the the river training engineers and the technology sorrow of China”. The 700 km long lower reaches of levee defence was developed. Because of have moved across throughout the north China population growth, the flood diversion strategy plain leaving numerous old channels. was more difficult to implement. Pan Jixun proposed the strategy of narrowing the river Controlling the Yellow River has a history of and confining the flood within the mainstem more than 3,000 years. Levee construction channel, in order to raise the velocity and keep 4 the carrying capacity of the flood high, preventing control and flood mitigation. The wide river sediment from depositing and even promoting bed and depositing sediment strategy can essentially sediment scouring. He regulated the levee system, mitigate flood disasters and reduce levee breaches blocked many branches of the river and made for a long term period of time. The paper also the river flow in a single channel in the lower discusses the new challenges and new strategies reaches in the period 1565-1592. After Pan Jixun, for Yellow River training and management. The sediment deposition in the lower Yellow River Sanmenxia Project was the first large dam on the channel increased to 5-10 cm per year. The river Yellow River, and was regarded as a failure of migrated from south to north and captured the the modern river training, because the extremely Daqing River in 1855 due to the levee breach at high rate of sedimentation caused floods in the Tongwaxiang. Weihe River and the benefit from hydro power generation was reduced to the minimum. The last Since the 1950s the Yellow River Water chapter discusses the merits of the project, its role Conservancy Commission (YRCC) has been the in the river training strategy and the future fate of leading body for river training. Wang Huayun, the the dam. chief of the YRCC, proposed and implemented his training strategies in this period. The main Key words: Yellow River, Levee breaches, strategies are to reduce flood discharge with Avulsion, Wide river and depositing sediment reservoirs, enhance the capacity of the river strategy, Narrow river and scouring sediment channel by enhancing and reinforcing the levees, strategy, Sanmenxia Reservoir, Land creation. and retaining floodwater in detention basins. These strategies are referred to in short as: build a wide river and reinforce the levees, upper reaches storing, lower reaches discharging and two sides retaining. Wang’s strategy is almost the same as that proposed by Wang Jing. This paper analyzes the levee breaches and flood disasters in the past 2000 years and the compares results of the two extremely different strategies. The narrow river and scouring sediment strategy has only short term effects on levee breach 5 CONTENTS Abstract....................................................................................................................4 Contents...................................................................................................................6 1. Flood Disasters and avulsions of the lower yellow river.................................................9 1.1 The Yellow River Basin...........................................................................................10 1.2 Flood Disasters in History......................................................................................13 1.3 Avulsions of the Lower Yellow River.........................................................................18 1.4 Soil Erosion caused Frequent Levee Breaches.........................................................24 2. TWO THOUSANDS YEARS OF DEBATE ON CONTROL STRATEGIES..................................33 2.1 Controlling the Yellow River...................................................................................34 2.2 Debates on Control Strategies..............................................................................40 2.3 Modern Flood and Sedimentation Control Methods.................................................45 3 NEW CHALLENGES AND NEW STRATEGIES.................................................................55 3.1 New Flood Threat due to Human Activities..............................................................56 3.2 Water Resource Development Affecting Fluvial Processes .......................................62 3.3 Land Creation and Land Loss in the Yellow River Delta.............................................69 3.4 New Strategies....................................................................................................73 4. THE SANMENXIA PROJECT AND ITS MERITS...............................................................76 4.1 Sanmenxia Reservoir.............................................................................................77 4.2 Management of Reservoir Sedimentation................................................................81 4.3 Sedimentation of the Weihe River...........................................................................86 4.4 Equilibrium Sedimentation Model...........................................................................92 4.5 Changing River Patterns........................................................................................93 4.6 Erosion and Resiltation below Sanmenxia Dam.........................................................94 Conclusions..............................................................................................................97 References................................................................................................................98 6 7 8 1. Flood disasters and avulsions of the lower Yellow River 9 1.1. The Yellow River Basin The Yellow River shown in Fig. 1 has a drainage erosion and sedimentation that make the river area of 795,000 km² and a length of 5,464 km, channel extremely unstable. The river watershed making it the second longest river in China. The is mostly arid and semi-arid with a long-term river is divided into its upper reach, middle reach mean annual runoff depth of only 77 mm and and lower reach for convenience of management a total annual runoff 58 billion m³. The water and discussion. The upper reach extends from resource per capita of the watershed