译言维基项目管理：清华大学王兆印教授英文教材《流域综合管理》第六章试译-1
目录 |
第六章：冲积河流的防洪和水沙管理 ——以黄河为例 CHAPTER 6 FLOOD DEFENSE AND WATER AND SEDIMENT MANAGEMENT - WITH PARTICULAR REFERENCE TO THE YELLOW RIVER
清华大学王兆印教授英文教材《流域综合管理》第六章试译 第六章：冲积河流的防洪和水沙管理 ——以黄河为例 CHAPTER 6 FLOOD DEFENSE AND WATER AND SEDIMENT MANAGEMENT - WITH PARTICULAR REFERENCE TO THE YELLOW RIVER
项目创建后，项目的主页面应该已经存在了，作为项目发起人，您需要对该页面进行完善。
项目主页面的基本格式为：
|
第六章：冲积河流的防洪和水沙管理 ——以黄河为例 6.1洪水灾害和防洪 黄河的管理可以作为冲积河流管理的例子。由于黄河携带了大量的泥沙，曾经是中国灾害最严重的河流，所以管理难度非常大。半个世纪以来，黄河被成功地固定在大堤内,但是新的问题又引起了社会的广泛关注。比如，为了满足持续增长的用水需求的引水引起了河流干涸；河漫滩的开垦和泥沙淤积使得在两年一遇的洪水水量下就可以达到历史最高水位。为了适应河流治理和管理所做的各种努力，河流综合管理显得比以前更加重要。
6.1.1黄河流域 黄河是中国的第二长河，全长5464 ，总流域面积为752，000 。黄河，是中华文明的摇篮，是世界上最具挑战性的一条河流。它的高含沙量经常造成侵蚀和泥沙淤积，使得河床非常不稳定。流域大部分属于干旱、半干旱地区，多年平均径流深只有77 ，总水量多年平均为580亿 ，人均水资源量为每年593 ，只有全国平均水平的四分之一。80年代之前年平均泥沙输移量为16亿吨，排名世界第一，最高的时候达到年39亿吨。平均含沙量为35 ，最高含沙量911 。最高年水量和最低年水量的比值为3.4，而最高的泥沙含量和最低泥沙含量的比值为10。60%以上的水和85%以上的沙都集中在每年7月到10月的汛期。 表6.1 黄河长期水沙量 表6.2 黄河下游洪水特征值 注意：小浪底——花园口指的是小浪底和花园口之间的流域来水量，不受黄河上水库的控制。 黄河下游的泥沙主要由粉沙（0.002—0.02 ）组成，其矿物质成分主要有石英、长石、方解石、伊利石。泥沙很容易就悬浮起来，而却观察不到床沙质的运动。如表6.1中是由40多年的观测值得到黄河的长期平均流量和平均泥沙量。表6.2所示的是防洪设计流量重现期。黄河的泥沙堆积在河口和华北平原，营造了多达250 000 的肥沃土地，形成了顶点在郑州的潘黄河三角洲。这片大约有1亿5千万人口居住土地，是中华民族的宝贵财富。图6.1表示了黄河流域和潘黄河三角洲。
图6.1:黄河和潘黄河三角洲，潘黄河三角洲上的黄河下游河道曾多次迁移（Wang and Liang, 2000）[ ]。
6.1.2历史上的洪灾 有史以来，黄河就和洪水、饥荒联系在一起了。黄河携带了从黄土高原由于土壤侵蚀而产生的大量泥沙并在河床和河口淤积。徐（1998年）[ ]借助于地图对比、文献研究、现代化数据处理和 衰减的手段研究了黄河下游的泥沙堆积速率。他把过去的13 000年分成为四个阶段，如图6.2a所示，1）从公元前11 000年到公元前3 000年是一个泥沙淤积速度低的时期，平均每年的淤积速度只有0.2 ；2）从公元前3 000年到公元600年，由于气候的变化，泥沙淤积加速。在这个时期泥沙淤积速度增加到每年0.5 ；3）公元600年到公元1855年，由于人类活动使泥沙淤积速度增加，平均年淤积量增加到1-3 ；4）从1855年开始，人类的活动对泥沙淤积速度的影响达到了一个极高的水平。泥沙淤积的速度达到5-10 每年。如图6.2所示，孙口横断面的测量值表明，黄河下游的泥沙淤积使河床和河漫滩区在过去的70年里抬高了5米。孙口是黄河下游典型的横断面，不宽不窄，处于黄河下游的中段。 最终，一条经常破坏大堤的悬河形成了。从公元前602年到1949年，黄河见证了1 593次决堤，大部分地方洪水泛滥543年，夺走了成千上万人的性命。洪水使黄河的主河道绕着顶点在郑州附近改道26次，带来了破坏性的灾难，留下了大量的古河，其中8次（5次是自然移动，3次是人为造成的）主要的迁移是在渤海和黄海交互的河口地带。因为其不受控制的行为，黄河下游被称为“中国的悲哀”。700 长的下游河道扫荡了华北平原，留下大量的古河道。图6.3显示了黄河从公元前602年到1855年的变迁、古河道和黄河塑造的陆地。
图6.2（a）是在四个不同时期内黄河下游的泥沙淤积速度（徐，1998）[2]；（b）1933-2002年期间泥沙淤积使孙口横断面的抬高。（孙口在郑州下游300 ，河口上440 ）
下面简略列举一下历史上最严重的洪灾：
1117年——黄河下游因大雨引发了一场大洪水，河堤多个地方决口，一百多万人在这场洪水中丧生。
1761年——从8月9日到8月18日连续下了10天雨，倾下100多亿 水，造成了一场罕见的洪水。黑港口到花园口的断面上，洪峰流量达到32 000 。河南、山东和安徽共26个乡受灾。
1843年——8月6日到8日，黄河中游发生一场暴雨，导致了这场历史上最大的洪水（1 000年一遇）。山县到三门峡河段的洪峰流量达到36 000 ，12天的总流量大于119亿 。潼关到小浪底的洪水水位是1 000年来的最高水位。26个乡，15 000个村庄受到洪灾，成千的人丧生。
1855年——从1796年到1855年，黄河的大堤决口22次，当时河流整治的主要任务是把决口堵上。上游的一场洪水在下游被一场大雨放大，1855年6月18日铜瓦厢（图6.1）决堤。洪水奔涌而出，淹没了8个乡，并最终抢夺了大庆河的河道。结果，黄河的主河道从南面移到北面汇入渤海。几千人在洪水中丧失性命，几百万人流离失所。
图6.3 黄河河道的迁移和废弃的河道 1933年——1933年8月5日到10日的大雨又让河水暴涨。黄河的支流青涧河流域的四天降水量达到255 。山县站记录的洪峰流量为22 000 。洪水引起54处堤防溃决，淹没了67个乡共8637 的地区，18293人丧生。
图6.4（a）由于人为炸开花园口大堤形成的洪水，洪水在平原上肆虐，最后流入淮河，这造就了54000km2的黄泛区。（b）这场洪水中，890 000人丧生，390万人流离失所。这张图显示的是1938年人们正在撤离他们被洪水侵袭的家乡。
1938年——1938年6月9日，中国军队为了阻止日本军队的入侵，炸开了花园口的大堤，河水倾斜而出，淹没了50 000 的范围，最后夺走了淮河的河道。结果，黄河主道又从北边移到了南边，此后八年都流入淮海，如图6.4a所示。890 000人丧生，390万人流离失所。黄河在没有固定河道的淮河河道内，在没有大堤的平原上流了八年。它携带的100亿吨泥沙淤积形成了54 000 有名的“黄泛区”，那里就像沙漠，低产而且植被稀少。如图6.4b所示，1938年人们正在撤离他们被洪水侵袭的家乡。
1958年——三门峡和花园口之间下了一场5天降水量达到198 的暴雨，花园口记录的洪峰流量为22 300 ，为了减少对下游的威胁，利用了东平湖滞洪区滞洪。黄河大堤没有决口，但是大堤内的漫滩区和滞洪区的1 700多个村庄受灾。
6.1.3 历史上的黄河整治 中国的防洪史基本上是人们和黄河洪水的斗争的历史，因为黄河的洪水是最具灾难性的。由于其高含沙量，黄河的治理也是最具挑战性的。黄河的治理有3 000年的历史了。大堤的修建是防洪的最主要的策略。2 200年以前，秦王朝统一全国，把防洪堤连成一个完整的堤防系统，黄河下游被限制在大堤内，但是由于泥沙淤积抬高了河床，使得黄河河道经常迁移。人们发展了各种策略来治理河流，其中最具影响力的是宽河理论和束河理论。宽河理论是指把河流固定在一个由大堤约束的河谷内，用分洪渠道分洪。汉王朝的大臣王景是这个策略主要的尝试者。另一个策略是束窄河流，把水流限制在主河槽内，提高了水流流速，从而使水流保持较高的挟沙能力，防止泥沙淤积甚至冲刷河道。明王朝的大臣潘季驯是这一策略最杰出的拥护者和实践者。
从公元前168年到公元69年，黄河非常活跃，多次发生洪水和改变河道。从公元前69年开始，王景贯彻实施了一个大规模的整治工程。他修筑并加高了河堤，建设了很多分洪渠道和线路。他的措施中有一个是在大堤内建设平行的小堤，沿着这些内堤，每个堤都建有距离为5 的闸门。河内的小堤比两岸的大堤要低，重大事故发生时，洪水会漫过河内小堤但是依然在大堤之内。当洪水量减少时，这些门就敞开，水就又可以流回到河道内。河道很宽，一般来说河是被约束两个相距上十公里的大堤之内。河床以每年1 的速度慢慢淤积。同时，黄土高原由原来的农业转为节约耕种，这样就减少了产沙量和进入河道内的泥沙量。在这之后的800年黄河相对平静，没有灾难性的洪水发生。（Li,1992）[ ]
从公元850年到公元1500年，黄河“苏醒”后又非常活跃。在这个时期，大堤每两年决口一次。对于河流治理的工程师们来说，堵塞溃决的大堤是一项非常艰苦的工作，因此堤防的防护措施也得到了发展。徐友征采纳了利用渠道和堰分洪的策略，并在1450年到1456年建成了沙湾滞洪工程。由于人口的增长，分洪的策略越来越难执行。潘季驯提出束窄河流，把洪水束缚在主河槽上，从而使水流流速增大，挟沙能力增大的策略，从而防止泥沙淤积，甚至可以促进河床泥沙的冲刷。从1565年到1592年，他规整了大堤系统，阻塞了一些分支，使黄河在下游只沿着一条河道流动。他的贡献使得黄河相对稳定。
束河的策略在潘季驯之后没有得到很好的贯彻，泥沙淤积速度达到每年5~10 。1885年，由于在铜瓦厢决口，黄河的主河道从南侧移到北侧并抢夺了大清河的河道。大改道后的前十年，由于没有坚固的堤防来处理这些水，政府又在到底是把河道改回去还是再修建一条新的堤防系统以稳定北侧河道上犹豫不决。最后，山东巡抚丁宝征决定利用省内资金，通过加固堤防，疏宽一些较窄的断面来稳定河道。从1864年到1888年，新的地方堤防系统修建完毕，从此黄河通过利津流入渤海。
二战期间，黄河在1938年又人为的移回南侧，河水在没有河堤的黄淮平原上流着。灾难性的后果使当地人们强烈要求政府要么把河道移回北侧，要么在黄河和淮河之间确定一条新的河道。1945年，政府和水利工程师们作过努力以堵上决口，把河移回北侧河道，但是失败了。1946年水利工程师们最终堵上了决口，又一次使黄河从北侧的河道穿过山东省入海。如图6.5是一张堵南侧大堤决口的图片，这也宣告了黄河在华中平原8年水灾的结束。
图6.5 溃决的黄河南侧大堤在1946年被堵上。这也结束了黄河在华中平原的8年水患。 从1950年开始，黄河水利委员会就是黄河治理的领导组织。在这时期内，黄河水利委员会主任王化云提出并实施了他的治河策略（Wang,1989）[ ]。国家花了10亿来防洪，减少了5000亿的洪水损失。河床轮廓已经保持了半个多世纪的稳定，只是由于河口向海内延伸从而使河床平行抬升（Zhang and Xie 1985）[ ]。最主要的措施是用水库来控制洪水流量，通过加固整治大堤来提高河道的行洪能力，向滞洪区分洪等。简单来说就是：上拦下排，两岸分治。 在黄河的治理过程中，有三个外国人的名字必须提到：恩戈尔斯，弗里曼和弗兰休斯（Yen,1999）[ ]。弗里曼1917年访问中国，建议在黄河下游从大堤开始修建相距大于6 丁坝。弗里曼的建议再次引发了大堤是应该靠近还是像当时那样远离河道的争论。恩戈尔斯在1931-1934年指导了中国经济委员会负责的物理模型试验。试验的结果显示，大堤远离河道主槽时将比靠近河道主槽产生更好的冲刷（Engels,1932年）[ ]弗兰休斯指导了另外一个模型试验，但是得到了不一样的结果。Yen指出，弗兰休斯的试验缺少边界条件，因此和恩戈尔斯的试验结果不符合（Yen,1999）[6]。 6.1.4治河理论 一些河流治理的理论如下： （1） 田蚡的顺其自然理论（两千多年前的汉王朝）
河流自然移动，人类没有必要去治理它。减少洪水灾害损失的唯一方法是撤离风险区让洪水自由流动。在田蚡的那个年代，黄河大堤发生过一次决口，河流流入华北平原达23年之久，这给人们带来灾难但同时也营造了肥沃的土地。
（2） 无堤河谷理论
这个理论认为河流应该在低地上流动，不必有河堤。如果原来的河道被淤死，它自己就会移到一条新的河道里。
（3） 人为移动理论 如果原来的河道被淤死，则人们应该把它导向一条新河。人们也可以利用河水来抵抗敌军的侵略，1112年和1938年就用过。 （4） 用分洪渠分洪 为了减少洪水的损失，分洪渠道是必要的。 （5） 滞洪区 利用滞洪区来滞留洪水，从而保证低处人们的安全。 （6） 束水攻沙理论 用大堤和丁坝束窄河道，堵塞河道的分支，把河流束缚在一条河道内从而增大流速，增强水流的挟沙能力，用来阻止泥沙淤积，冲刷河床（潘季驯）。 （7） 上拦下排，两岸分滞理论 最近50年防洪实践的指导性理论是：利用上游的水库减少洪水流量，通过加高加固堤防增加下游的输沙能力，利用两岸的滞洪区阻止罕见的洪水。简单的说，就是“上拦下排，两岸分滞”。
CHAPTER 6 FLOOD DEFENSE AND WATER AND SEDIMENT MANAGEMENT - WITH PARTICULAR REFERENCE TO THE YELLOW RIVER
Management of the Yellow River is presented as a case study for alluvial river management. The river is difficult to manage because it carries a heavy sediment load and used to be the most disastrous river in China. The river has been successfully kept flowing within the grand levees for a half century. But new problems have attracted attention of society, for example, the water diversion to meet increasing water demand caused drying up of the river, floodplain reclamation and sedimentation of the channel resulted in a historically high water stage. Integrated river management is more necessary than before to coordinate various efforts of river training and management.
6.1 FLOOD DISASTERS AND FLOOD DEFENCE
6.1.1 THE YELLOW RIVER BASIN The Yellow River shown in Fig. 6.1 has a drainage area of 795,000 km2 and a length of 5,464 km making it the second longest river in China. The long-term annual sediment load at Sanmenxia Station was 1.6 billion tons before 1980, with a highest annual load of 3.9 billion tons. The river ranks first of all the world’s rivers in terms of sediment load (Qian and Dai, 1980), although the sediment load has reduced greatly in the past 20 years. The long term (1950-1985) average sediment concentration was 40 kg/m3 and the highest sediment concentration was recorded at 911 kg/m3. The ratio of the highest annual runoff to the lowest is 3.4 and the ratio of the highest annual sediment load to the lowest is 10. More than 60% of the water and 85% of the sediment are transported in the flood season from July to October. The Yellow River, recognized as the cradle of Chinese civilization, is the most challenging river in the world. It carries the heaviest sediment load and often experiences erosion and sedimentation that make the river channel extremely unstable. The river watershed is mostly arid and semi-arid with a long term-average annual runoff depth of only 77 mm and total annual runoff 58 billion m3. The water resource per capita in the watershed is only about 500 m3, only one quarter of the average in China.
Fig. 6.1 The Yellow River basin, tributaries and important hydrological stations
The sediment load of the lower Yellow River is mainly composed of silt; its mineral composition is quartz, feldspar, calcite, and illite. The sediment is readily suspended and no distinct bed load motion can be detected. Table 6.1 lists long term average values of water discharge and sediment load of the river; they are obtained by averaging over 39 years (1950-1989) of recorded values. Table 6.2 lists the discharge of floods of various recurrence periods for flood control design. The river deposits sediment at the river mouth and on the north China plain and has created more than 250,000 km2 of fertile land forming the Pan Yellow River Delta with the apex at Zhengzhou. The land, on which about 150 million people are dwelling, is a great benefit to the Chinese people and nation.
Table 6.1 Average water and sediment load of the Yellow River in the period from 1950-1989 Hydrologic Station Huayuankou (Zhengzhou) Lijin (Dongying) Annual Runoff 43 billion m3 30 billion m3 Annual Sediment Load 1.6 billion tons 1.0 billion tons Average Sediment concentration 40 kg/m3 33 kg/m3 Median diameter of suspended sediment 0.019 mm 0.019mm Maximum day-average discharge 6,860 m3/s 5,400 m3/s
Table 6.2 Flood features of the lower Yellow River (Chen, 1999) Hydrological Station Catchment (km2) Peak discharge (m3/s) 5 days runoff (bm3) 12 days runoff (bm3) 100yrs 1000 yrs 100 yrs 1000 yrs 100yrs 1000 yrs Huayuankou 730,036 29,200 42,100 7.13 9.84 12.5 16.4 Xiaolangdi 694,155 29,200 42,100 6.24 8.70 10.6 13.9 Sanmenxia 688,421 27,500 40,000 5.91 8.18 10.4 13.6
6.1.2 FLOOD DISASTERS IN THE HISTORY Throughout the history of China, the Yellow River has been associated with floods and famine. The river carries sediment produced by soil erosion from the Loess Plateau, which deposits on the channel bed and in the estuary. Xu (1998) studied the sedimentation rate of the lower Yellow River applying map comparison, historical literature studies, modern data analysis, and 14C dating. He divided the past 13,000 years into 4 periods, as shown in Fig.6.2: 1) from 11,000 BC to 3,000 BC is a period of low sedimentation with an average sedimentation rate of only 0.2 cm per year; 2) from 3,000 BC to AD 600 is a period with accelerated sedimentation due to climate changes. The sedimentation rate increased to about 0.5 cm per year in this period; 3) from AD 600 to 1855 is a period with accelerated sedimentation caused by human activities. The average sedimentation rate increased to 1-3 cm per year; 4) since 1855 human activities have accelerated the sedimentation at an extremely high degree and the sedimentation rate has risen to 5-10 cm per year. The measured transverse riverbed profile at the Sunkou cross section in Fig. 6.3 shows that the sedimentation of the lower Yellow River raised the riverbed and floodplain by about 5 m in the past 70 years. Sunkou is a typical cross section in the lower Yellow River, which is not very wide and not narrow and is located at the middle of the lower reaches of the river.
Fig. 6.2 Sedimentation rate in the lower Yellow River during the 4 historical periods: 1) geological sedimentation; 2) sedimentation due to climate change; 3) sedimentation due to human activities; 4) accelerated sedimentation due to human activities (after Xu 1998);
Fig. 6.3 Sedimentation caused changes in the riverbed at the Sunkou cross section during the period 1933-2002 (Sunkou is 300 km downstream from Zhengzhou and 440 km upstream from the river mouth)
Over time, a perched river formed that frequently breached its levees. From BC 602 to 1949 the river experienced 1,593 levee bursts, flooding vast areas in 543 years and claiming millions of human lives. The river shifted its major course (600-700 km long) by avulsion 26 times with the apex around Zhengzhou resulting in devastating calamities and numerous old channels, including 8 major shifts (5 natural and 3 human-caused) with the river mouth alternating between the Bohai Sea and the Yellow Sea. Because of its wild behavior, the lower Yellow River was dubbed “the sorrow of China”. The 700 km long lower reaches have swept throughout the north China plain and left numerous old channels. Figure 6.4 shows the migration of the river from BC602 to 1855 and the old channels and the land created by the river.
Fig. 6.4 Migration of the Yellow River and the abandoned channels
The most disastrous floods are briefly summarized as follows: (IWHR and WUHEE, 1985)
1117-A high flood occurred in the lower Yellow River due to heavy rainfall and the river levee was breached at many places. More than one million people were killed by the flood. 1761-Ten days of rainfall from August 9 to 18 resulted in 10 billion m3 of runoff and caused a rare flood with a crest discharge of 32,000 m3/s in the section from Xiaolangdi to Huayuankou. Twenty-six counties in Henan, Shandong and Anhui Provinces were flooded. 1843-A rainstorm occurred in the middle reaches of the Yellow River on August 6-8 and generated the biggest flood in recorded history (1000 yr reoccurrence). The crest discharge in the reach from Shanxian to Sanmenxia was up to 36,000 m3/s and the total runoff in 12 days was over 11.9 billion m3. The flood stage in the reach from Tongguan to Xiaolangdi (Fig. 6.1) was the highest in 1000 years of history. Twenty-seven counties and 15,000 villages were flooded and thousands of people were killed. 1855-From 1796 to 1855 the Grand Levees were breached 22 times and the major task for the river training was to close the breaches in this period. A flood from the upstream magnified by a heavy rainfall in the lower reaches breached the grand levee at Tongwaxiang on June 18 ,1855. The river poured out and inundated 8 counties, and finally took over pirated the Daqing River Channel. Consequently, the Yellow River shifted its major course from south to north and flowed into the Bohai Sea. Thousands of people were killed by the flood and several million people lost their homes shelters and farmland. 1933-In 1933 the river swelled again by heavy rainfall during August.5-10. The 4 days of precipitation in the Qingjian River (a tributary of the Yellow River) watershed reached 255 mm. The crest discharge was recorded at 22,000 m3/s at Shanxian Station. The flood caused 54 levee breaches, inundated 67 counties with a total flooded area of 8,637 km2 and killed 18,293 people. 1938-On June 9, 1938 the embankment at Huayuankou was broken by the Chinese army attempting to stop invasion by the Japanese army. The river emptied itself through an inundated land area of about 50,000 km2, and finally captured the Huaihe River channel. Consequently, the river shifted its major course from north to south and flowed into the Yellow Sea for 8 years, as shown in Fig. 6.5. More than 890,000 people were killed and 3.9 million people lost their homes and farmland. The river flowed on the plain without any fixed channel and levees and in the Huaihe River channel for 8 years. It brought about 10 billion tons of sediment deposition and created the Huangfan flooded area of 54,000 km2, which is desert-like land with low productivity and poor vegetation. Figure 6.6 shows that people were escaping from their flooded homeland in 1938.
Fig. 6.5 Extent of the man-made flood caused by exploding the levee at Huayuankou in 1938. The flood water flowed on the plain and finally flowed into the Huaihe River, which created the 54,000km2 Huangfan desert;
Fig. 6.6 About 890,000 people were killed and 3.9 million people lost their homes and farmland. This figure shows people escaping from their flooded homeland (after YRCC, 2001).
1958 – A heavy rainstorm occurred in the drainage area between Sanmenxia and Huayuankou with 5 days of rainfall totaling 198 mm. The crest discharge at Huayuankou was recorded at 22,300 m3/s and the Dongping lake flood detention basin was used to reduce the threat to the lower reaches. The major levees were not broken but 1700 villages on the floodplain within the Grand Levees and in the flood-detention basin were flooded.
6.1.3 HISTORIC TRAINING OF THE RIVER The flood defense history of China is essentially a history of the people's struggle against Yellow River floods because the floods were disastrous and training of the river is most challenging due to the heavy sediment load. Training of the Yellow River has a history of more than 3,000 years. Levee construction was the major strategy of flood control. The Qin Emperor united the country and linked the flood defense levees into an entire levee system about 2,200 years ago. The lower Yellow River was confined within the levees but sediment deposition raised the riverbed and made the river frequent shift its course. People developed many strategies to harness the river, among them the wide channel and narrow channel theories had the most influence. The wide channel theory is to confine the river within a wide river valley with levees and divert floods with diversion channels. Wang Jing- a minister of the Han Dynasty (206 BC to 220 AD)- was the major practitioner of the strategy. The second strategy is to narrow the river and confine the flood within the stem channel in order to raise the velocity and keep the high carrying capacity of the flow, preventing sediment from depositing and even scouring the bed. Pan Jixun- a minister of the Ming Dynasty (1368-1944)- was the most outstanding advocate and performer of this strategy. In the Han Dynasty, Jia Rang proposed three river harnessing strategies: (1) widen the river channel and construct flood diversion basins to enhance the flood conveyance capacity of the river and mitigate flood disasters; (2) build gates and diversion channels, divert flood water through diversion channels into the Zhanghe River and other rivers; and (3) enhance and reinforce the levees every year. The main principle of Jia Rang was to give enough space for the river channel and flood flow. Any agricultural development should not occupy the flood plain, which was necessarily a flood way. From 168 BC to 69 AD, the river was active; it flooded and changed its course several times. Wang Jing implemented a large-scale training project in 69 AD. He completed and enhanced the levees and built many diversion channels and weirs. One of his strategies was to build inner levees parallel within the Grand Levees. Along the inner levees, he constructed many gates about 5 km apart. The inner levees were lower than the Grand Levees. During great events water flowed over the inner levees but was still controlled by the Grand Levees. As the flood receded, the gates were open allowing water to flow back to the inner channel. The channels were wide. Generally speaking the river was confined by the enhanced levees tens of kilometers apart. The riverbed silted up at a low speed of about 1-cm per year. In the meantime the major land use in the Loess Plateau changed from agriculture to husbandry, which reduced sediment yield and sediment load into the river. In the following 800 years the river was calmed and no big flood disasters occurred (Li, 1992). From 850 AD to 1500 AD the river woke again and became very active. The Grand Levee was breached once per 2 years during the period (IWHR and WUHEE, 1985). Closing the breached levee was a hard job for the river training engineers and the technology of levee defence was developed. Xu Youzheng adopted the strategy of diverting floods with channels and weirs and implemented the Shawan Flood Diversion Projects in 1450-1456. Because of the population growth, the flood diversion strategy was more difficult to implement. Pan Jixun proposed the strategy of narrowing the river and confining the flood within the stem channel in order to raise the velocity and keep high the carrying capacity of the flood, preventing sediment from depositing and even promoting bed sediment scouring. He regulated the levee system, blocked many branches of the river and made the river flow in a single channel in the lower reaches in the period 1565-1592. The river became relatively stable thanks to his effort. The strategy of narrowing the channel was not properly applied after Pan Jixun and the sediment deposition in the channel sped up to 5-10 cm per year. The river migrated from south to north and captured the Daqing River in 1855 due to the levee breach at Tongwaxiang. In the first 10 years after the major shift of the river course, the river flowed wildly and flooded frequently because there were no strong levee to accommodate the river water and the government hesitated to move the river back to the south or build a new levee system to stabilize the north channel. The governor of Shandong Province, Ding Baozheng, decided to stabilize the river by reinforcing the levees and widened a few narrow sections with local and state funds. From 1864-1888 the new dyke system was constructed and since then the river has flowed into the Bohai Sea via Lijin. Since the river was artificially shifted to the south in 1938 during the second World War, the river flowed over the plain without any levee between the Yellow River and the Huaihe River. It was disastrous and the local people appealed to the government to bring the river back to its north channel or to fix a channel between the Yellow and Huaihe Rivers. In 1945, the government and hydraulic engineers made an effort to close the breach and bring the river back to its north channel but failed. In 1946, hydraulic engineers finally closed the breach and made the river flow in the north channel across Shandong Province again. Figure 6.7 shows a photo of the closing of the breached south levee, which ended the 8 years flooding of the Yellow River water over the central China plain.
Fig. 6.7 The breached south levee of the Yellow River was finally closed in 1946, which ended the 8 years of flooding of Yellow River water over the central China plain. (after YRCC，2001)
Since the 1950s the Yellow River Water Conservancy Commission (YRCC) has been the leading institute for river training. Wang Huayun, the chief of YRCC, proposed and implemented his training strategies in the period (Wang, 1989). The nation has spent $1 billion for flood control and saved $500 billion in flood losses (Chen 1999). The riverbed profile has remained stable for half a century, with only parallel rising following the extension of the river mouth into the sea (Zhang and Xie, 1985). The main strategies are to reduce flood discharge with reservoirs, enhance the capacity of the river channel by enhancing and reinforcing the levees, and retending floodwater with detention basins. These strategies are referred to in short as: upper reaches storing, lower reaches discharging and two sides retaining. Three foreign names should be mentioned who worked on the training of the river: Engels, Freeman and Franzius (Yen, 1999). Freeman visited China in 1917 and proposed to build cross dikes extending from the existing levees of the lower Yellow River, which were more than 6 km apart, and to build new levees near the tips of the dikes, 800 m apart (Freeman, 1922). Freeman’s suggestion rekindled the century’s debate on whether the levees should be close or far apart as they were at the time. Engles conducted physical model experiments, authorized by the Chinese National Economic Council in 1931-1934. The test results indicated that with the levees set far apart, a somewhat better scour was produced in the main channel than when the levees were close to the main channel edges (Engels, 1932). Franzius conducted another physical model experiment and obtained different results. Yen (1999) indicated that Franzius’ experiments were conducted without tail gate regulation and the results are not reliable as those of Engels .
6.1.4 RIVER TRAINING THEORIES
Many river harnessing theories have been advocated. including:
(1) Naturalization theory proposed by Tian Fen (Han dynasty 2000 years ago)
It is the river’s nature to move and people cannot harness it. The only way to reduce flooding losses is to evacuate the area at risk and freely allow river flooding over the land. A levee breach occurred and the river flowed over the north China plain for 23 years during Tian-Fen time, which caused disasters to the people but also created fertile land. (2) Leveeless river valley theory In this theory the river should flow over low ground without levees. It will shift to a new low land if the old one is silted up. (3) Artificial migration theory If the old channel is silted up, people may guide the river to a new channel. People may also utilize the river to resist an invading enemy army, which was practiced in 1112 and 1938. (4) Flood diversion with branch channels Flood diversion channels are necessary to reduce flood damages. (5) Flood diversion basins Build flood diversion basins to retain flood water in order to protect people in the lower reaches. (6) Narrowing channel and enhancing sediment carrying capacity Narrow the channel with levees and spur dikes, cut branch channels, and confine the flood in one channel to enhance the flow velocity and the sediment carrying capacity of the flow, to prevent sediment deposition and scour the channel bed (Pan Jixun). (7) Upper reaches storing, lower reaches discharging and two sides retaining. The theory which has guided the flood control practices in the past 50 years are: Reducing flood discharge with reservoirs in the upper reaches, enhancing discharge capacity of the lower reaches channel by enhancing and reinforcing the levees; and retaining rare flood water with detention basins on the two sides of the river.
注意
|
|
关于页面编辑请参见编辑页面。
文章页面是一个项目的重要组成部分，作为项目发起人，您需要逐一创建每篇文章的页面，并将该篇文章的原文手动粘贴进该页面。
创建文章页面需要按照一定的规则来命名，一般按照
| 项目名：文章名 |
来命名文章页面。
创建所有的文章页面后，您应该在该项目主页面中创建指向这些页面的链接，并对这些链接进行排序，规范格式。
关于创建页面请参见创建新页面。
