DEEP THOUGHTS OF LAND UTILIZATION ABOUT THE RARELY SEVERE FLOODING DISASTERALONG THE MIDDLE AND LOWER REACHES OF THE CHANGJIANG RIVER IN 1998

In the summer of 1998, a rarely severe flooding disaster occurred in the whole basin of the Changjiang(Yangtze) River, which caused enormous losses. By 22nd of August, 29 provinces, autonomous regions and municipalitieswere involved, 21. 2 million ha of land were inundated, 223 million people were affected, 3004 people were killed and4. 97 million buildings were collapsed. The estimated direct loss of the country accounted to 166. 6 billion yuan (RMB).The main reason of the disaster is the unusual climate but the unreasonable land utilization the aggravated the disaster.This paper consists of two parts. One part analysed the unreasonable land utilization, including the neglect of forest landprotection, which caused the forest land area to decrease by 440 thousand ha in the whole country every year, the enclosing of lakes for cultivation, which decreased the area of lakes located along the banks of the Changjiang River from 17 200km2 at the beginning of the founding of the People’s Republic of China to 6531 km2 in 1983, the changing of functions oflakes, which reduced the volume of storage exceedingly, for example, only 5 spots of lakes were used for storing water inWuhan City, and the slow progress of the construction of flood diversion and storage area, which would cause huge lossesonce flood was diverted. The other part explored the strategy of land utilization on the supplying of land for flood controlprojects, such as embankment, drainage installation, flood diversion and storage area, and on tapping the potentialsthrough narrowing and amalgamgting the range of rural residential quarters and small towns, reclaiming reserved resources, transforming middle and low productive fields, attaching importance to land arrangement and recultivation, and adjusting contracted fields partially, to ensure the sustainable and stable growth of the region.

Natural Disasters of the Lower Reaches of Yellow River during the Longshan Period——The Natural Background of Dayu's Flood Control

It is very important to study the archaeological culture and origin of civilization in ancient China.The changes of the channels in the lower reaches of the Yellow River in the prehistoric period are part of the natural environmental background of the development of the ancient civilization in that area to be explored.This paper presents a series of legends,indications,scientific evidence,and macroscopic geographical background information of the evolution in the lower reaches of the Yellow River during the Longshan period.At first the river flowed from Northern Henan and Hebei to southwestern Shandong Province and Northern Anhui–Jiangsu provinces,and the mainstream of the Yellow River changed from the southeast to return to the north and flowed into the Bohai Sea in the late Longshan Period.During this period,floods were frequent.Various ethnic groups in the northern China plains suffered natural disasters and made great migrations which also contributed to the ethnic exchanges and integration.The people of the Central Plains made more dynamic adjustments in the relationship between mankind and the land by primitively escaping from the water and self–defensively controlling the rivers then to maintaining the local ecological environment by large–scale flood control measures,which promoted the settlement of Shandong,Henan,Jiangsu and Anhui provinces,the urban cultural development,and social evolution.Based on these events,the culture symbol of Dayu's Flood Control could be formed.

Research and Application of Rainstorm Disaster Risk Assessment along the Middle and Lower Reaches of Yangtze River

We explored and studied rainstorm disaster impact grade. Firstly,we selected average precipitation,precipitation intensity,coverage and duration during rainstorm process,and economic losses,the number of deaths and total casualties in rainstorm disaster situation as the pre-assessment indexes of rainstorm process impact grade along the middle and lower reaches of Yangtze River. Then,normalized and dimensionless processing of each index was conducted. By using gray correlation method,we established rainstorm process grade and rainstorm disaster impact grade. At last,we conducted regression analysis of relevancy degree between rainstorm process grade and rainstorm disaster situation grade,and established a linear relationship between the two,thereby getting a rainstorm disaster pre-assessment method. On this basis,using rainstorm hazard factors in independent sample,we carried out pre-assessment test of disaster impact grade. The results show that this pre-assessment method is quick and easy,and the effect is better.

Flood risk control of dams and dykes in middle reach of Huaihe River

Three stochastic mathematical models for calculation of the reservoir flood regulation process, river course flood release, and flood risk rate under flood control were established based on the theory of stochastic differential equations and features of flood control systems in the middle reach of the Huaihe River from Xixian to the Bengbu floodgate, comprehensively considering uncertain factors of hydrology, hydraulics, and engineering control. They were used to calculate the flood risk rate with flood regulation of five key reservoirs, including the Meishan, Xianghongdian, Nianyushan, Mozitan, and Foziling reservoirs in the middle reach of the Huaihe River under different flood frequencies, the flood risk rate with river course flood release under design and check floods for the trunk of the Huaihe River in conjunction with relevant flood storage areas, and the flood risk rate with operation of the Linhuaigang Project under design and check floods. The calculated results show that （l） the five reservoirs can withstand design floods, but the Xianghongdian and Foziling reservoirs will suffer overtopping accidents under check floods; （2） considering the service of flood storage areas under the design flood conditions of the Huaihe River, the mean flood risk rate with flood regulation of dykes and dams from Xixian to the Bengbu floodgate is about 0.2, and the trunk of the Huaihe River can generally withstand design floods; and （3） under a check flood with the flood return period of 1 000 years, the risk rate of overtopping accidents of the Linhuaigang Project is not larger than 0.15, indicating that it has a high flood regulation capacity. Through regulation and application of the flood control system of the Linhuigang Project, the Huaihe River Basin can withstand large floods, and the safety of the protected area can be ensured.

Engineering Strategies on Flood Control in Middle Reach of Yangtze River, China

Flood disaster has been a serious hidden danger since the ancient time. The essential cause for the fact that floods have not been eliminated for hundreds of years is that time honored strategies do not suit the cases of flood prevention. In the view of geological environmental analyses of flood formation and from the synthesis of experiences gained in flood control in the past hundreds of years, sluggish draining of flood, silt sedimentation in channel and building levee blindly constitute the main cause of intractable flood for a long time in the middle reach of the Yangtze River. Draining away silt and water is the only way to stamping out flood disaster. Opening up artificial waterways for flood diversion, draining away the silt of channel into the polders, and storing the flood water are important engineering measures for the flood control and damage reduction.

Flood and Waterlogging Disaster Damage Evaluation in Middle-Lower Yangtze River by 3S technology

The evaluation method, model and process for the flood and waterlogging disaster condition by GIS,RS and GPS technology and the method for setting up disaster condition database, dyke database and historical disaster damage database are presented. An index of flood damage degree(FDD) used to evaluate the relative degree of disaster loss and divide flood and waterlogging area is suggested. The value of flood damage degree can be calculated as follows :taking the various disaster losses of sample area in a base year as standard value and computing the ratios of various disaster loss values in different areas and years to the standard flood disaster loss values, then summing up the weighted ratios. The computed results are the value of flood damage degree in the every year. The macroscopic flood disaster distribution can be evaluated by the values of flood loss degree.

Large-scale atmospheric singularities and summer long-cycle droughts-floods abrupt alternation in the middle and lower reaches of the Yangtze River

The daily precipitation data at 720 sta- tions over China for the 1957―2003 period during summer (May―August) are used to investigate the summer subseasonal long-cycle droughts-floods abrupt alternation (LDFA) phenomenon and a long-cycle droughts-floods abrupt alternation index (LDFAI) in the middle and lower reaches of the Yangtze River (MLYRV) is defined to quantify this phenomenon. The large-scale atmospheric circula- tion features in the anomalous LDFA years are ex- amined statistically. Results demonstrate that the summer droughts-to-floods (DTF) in the MLYRV usually accompany with the more southward western Pacific subtropical high (WPSH), negative vorticity, strong divergence, descending movements develop- ing and the weak moisture transport in the low level, the more southward position of the South Asia high (SAH) and the westerly jets in the high level during May―June, but during July―August it is in the other way, northward shift of the WPSH, positive vorticity, strong convergence, ascending movements and strong moisture transport in the low level, and the northward shift of the SAH and the westerly jets in the high level. While for the summer floods-to-droughts (FTD) in the MLYRV it often goes with the active coldair mass from the high latitude, positive vorticity, strong convergence, ascending movement develop- ing and the strong moisture transport in the low level, and the SAH over the Tibetan Plateau in the high level, but during July―August it is often connected with the negative vorticity, strong divergence, de- scending movements developing and the weak moisture transport in the low level, the remarkable northward shift of the WPSH, the SAH extending northeastward to North China and the easterly jets prevailing in the high level over the MLYRV. In addi- tion, the summer LDFA in the MLYRV is of significant relationship with the Southern Hemisphere annual mode and the Northern Hemisphere annual mode in the preceding February, which offers some predictive signals for the summer LDFA forecasting in the MLYRV.

GEOGRAPHIC ENVIRONMENT CHANGE AND FLOOD CATASTROPHE IN HUAIHE RIVER BASIN DURING LAST 2000 YEARS

During the last 2000 years,flood and waterlogging catastrophes took place quite frequently in the Huaihe River Basin.In the authors’opinion,these natural calamities have a very close relation to the evolution of Hongze Lake.Formed initially within a man-made dyke that was built in the Han Dynasty about 2000 years ago, Hongze Lake brought out headward accumulation developing in the middle reaches of the Huaihe River, with its continuous aggravation on lake-bottom and consequent water-level rise. It was estimated that,on an average,there were 3400×104t sediment per kilometre per year deposited on the river bed from Lutaizi to Bengbu.Therefore,the rising of water-level and the drainage difficulty in the middle reaches of the Huaihe River aggravated local flood and waterlogging catastrophe here.

长江安徽段江湖连通性及生物通道恢复研究

江湖阻隔是导致长江中下游江湖复合生态系统衰退的最主要原因,江湖连通和生物通道恢复是流域生态修复的重要措施之一。通过现场调查等方法研究了华阳河湖群、菜子湖、升金湖和安庆西江古道等与长江干流的阻隔现状及连通性特征,在此基础上探讨了技术和管理层面存在的问题并提出对策建议。结果发现:依托涉水工程建设开展恢复河湖生物通道的做法可以有效缓解江湖复合生态系统的衰退,尤其是以“过鱼设施建设、季节性灌江纳苗、生态水网建设”相结合的生物通道恢复方案具有技术可行性。相关成果可为长江中下游江湖连通性及生物通道恢复、国家水网建设提供有益的参考。

The relationship between water level change and river channel geometry adjustment in the downstream of the Three Gorges Dam

In this study, data measured from 1955–2016 were analysed to study the relationship between the water level and river channel geometry adjustment in the downstream of the Three Gorges Dam（TGD） after the impoundment of the dam. The results highlight the following facts：（1） for the same flow, the low water level decreased, flood water level changed little, lowest water level increased, and highest water level decreased at the hydrological stations in the downstream of the dam;（2） the distribution of erosion and deposition along the river channel changed from ＂erosion at channels and deposition at bankfulls＂ to ＂erosion at both channels and bankfulls;＂ the ratio of low-water channel erosion to bankfull channel erosion was 95.5% from October 2002 to October 2015, with variations between different impoundment stages;（3） the low water level decrease slowed down during the channel erosion in the Upper Jingjiang reach and reaches upstream but sped up in the Lower Jingjiang reach and reaches downstream; measures should be taken to prevent the decrease in the channel water level;（4） erosion was the basis for channel dimension upscaling in the middle reaches of the Yangtze River; the low water level decrease was smaller than the thalweg decline; both channel water depth and width increased under the combined effects of channel and waterway regulations; and（5） the geometry of the channels above bankfulls did not significantly change; however, the comprehensive channel resistance increased under the combined effects of riverbed coarsening, beach vegetation, and human activities; as a result, the flood water level increased markedly and moderate flood to high water level phenomena occurred, which should be considered. The Three Gorges Reservoir effectively enhances the flood defense capacity of the middle and lower reaches of the Yangtze River; however, the superposition effect of tributary floods cannot be ruled out.

变化条件下长江下游地区防洪问题与韧性提升对策

长江下游地区圩区广布、城镇众多、水网稠密,汛期受长江上中游来水、长江口及沿海高潮和本地暴雨共同威胁。目前,该地区形成了以江河湖海堤防为基本屏障,以水库、湖泊和蓄滞洪区为洪涝调蓄空间,以长江及区域主要河道为洪涝行泄通道,各类闸站相配套的防洪治涝工程体系。但近年来长江流域大洪水事件表明,长江下游防洪工程薄弱环节仍然明显,蓄泄矛盾突出,空间统筹治理和工程协同调度不足,灾害风险预防管控存在盲区,同时还面临着气候水文和经济社会条件双重变化的复杂形势。为强化长江下游地区洪涝灾害风险集成调控、提升应对大洪水的韧性,需在稳固长江干流防洪屏障和行洪主通道的基础上,科学优化各水系洪涝蓄泄格局、加快补齐防洪基础设施短板、促进洪涝治理空间均衡协调、加强洪涝灾害风险管控预防、提升防洪管理智慧化水平。同时,还应针对长江下游地区重大防洪科技问题开展系统深入研究。

考虑径流过程矢量化的机器学习洪水预报模型

准确的超前洪水预报有利于开展防洪减灾工作和优化水资源调度。本文提出一种针对场次洪水的径流过程矢量化方法(Runoff Process Vectorization, RPV),并耦合3种机器学习(Machine Learning, ML)模型构建了RPV-ML洪水预报系列模型。以黄河中上游孤山川、佳芦河和祖厉河3个典型流域为研究区,分别基于43、28、37场洪水的降雨径流数据,按照洪水场次7∶3的比例进行模型训练和验证。研究表明:(1)相同预见期条件下RPV-ML模型在孤山川、佳芦河和祖厉河流域洪水预报纳什效率系数更高、均方根误差和洪峰相对误差更低,RPV-ML模型比ML模型具有更好的预报性能,在预见期为4~6 h时优势更显著;(2) RPV-ML和ML模型预报精度会随着预见期增加逐渐下降,但RPV-ML预报精度呈现缓慢下降趋势,具有更好的鲁棒性;(3)基于RPV改进的时间卷积网络(Temporal Convolutional Network, TCN)可以更好地克服预报误差问题,RPV-TCN模型在3个流域预报性能最好。

上海市洪涝灾害损失对长江下游地区的辐射影响

随着区域经济一体化程度的加深,跨区域产业关联损失已成为灾害损失评估不容忽视的一部分,准确量化洪涝灾害损失的辐射影响对于制定防灾减灾措施、减少洪涝灾害损失具有重要作用。在系统评估了不同暴雨重现期情景下上海市减停产损失的基础上,采用两区域投入产出模型,测算和分析了长江下游地区不同省(直辖市)的区域内乘数效应、区域间溢出效应和区域间反馈效应,量化了上海市洪涝灾害损失对长江下游地区的辐射影响。结果表明,暴雨重现期10 a、20 a、30 a、50 a、100 a时,上海市的减停产损失分别为14.01亿元、19.83亿元、25.58亿元、33.82亿元和46.24亿元;在长江下游地区,上海市与浙江省的经济相互影响强度最大,且跨区域产业关联损失以溢出效应为主导;上海市发生洪涝灾害时,跨区域波及效应将导致长江下游地区损失增加26.24%。因此,在城市之间联系日益紧密的情况下,不仅要关注洪涝灾害对自身的影响,同时也要采取有效措施减少地域之间的波及影响,以便更有效地开展防灾减灾工作。

长江中游干流河段洲滩民垸行蓄洪能力研究

长江中下游洲滩民垸具有巨大行蓄洪能力,对保障重点地区防洪安全起重要作用。但是,洲滩民垸点多面广,地形数据缺乏,无法充分利用并有效构建数学模型分析行蓄洪作用。基于长江中下游高分辨率遥感影像数据,构建长江中游干流河段洲滩民垸数字高程模型,以生产水位-面积-容积关系成果,分区分类研究洲滩民垸的行蓄洪能力。结果表明:长江中游干流洲滩民垸行蓄洪能力强,但空间分布差异大,其中,荆江河段洲滩民垸面积及蓄洪容积占比最高,在面临大洪水时调度运用多。研究成果能够直观有效呈现长江中游干流洲滩民垸的行蓄洪能力,为洲滩民垸的调度运用打牢数据基础,为科学准确制定防洪决策提供有力支持。

黄河宁蒙河段凌情灾害成因分析及防御措施研究

随着经济社会的高速发展,对黄河的防凌安全提出了更高的要求,研究凌情灾害成因及防御措施变化显得尤为重要。通过分析,影响宁蒙河段凌情变化的因素主要包括热力条件、水动力条件和河道边界条件。通过梳理1989年以来宁蒙河段典型凌灾情况,发现造成冰凌灾害的严重凌情多受剧烈天气过程、河道流量变化、复杂河道条件等因素影响。为避免宁蒙河段凌汛灾害,针对热力因素,应及早开展凌汛期气温凌情预报工作;针对水动力因素,应优化凌汛期水库群和分凌工程联合调度;针对河道边界条件,应提前拆除临时阻水建筑物,保证河道畅通,协调空军部队在险情发生时及时轰炸破冰,并加快黑山峡水利枢纽建设,恢复和长期维持较大的中水河槽过流能力,为宁蒙河段防凌防洪提供基本条件。

2024年2月初贵州东部及长江中下游低温雨雪冰冻天气的基本特征及成因

2024年2月初贵州东部及长江中下游出现低温雨雪冰冻天气,恰逢春运高峰,给春运、能源保供及人民生活造成严重影响。为揭示此次低温雨雪冰冻天气的异常特征,利用国家气象信息中心实况观测资料、美国国家环境预报中心和国家大气研究中心(NCEP/NCAR)再分析资料以及怀化双偏振雷达资料对此次天气的基本特征和成因进行了分析。结果表明:(1)2024年春节前贵州东部、湖南中北部、湖北东部南部及安徽西部北部出现4~6d严重冰冻灾害,冰冻灾害主要由两轮低温雨雪天气造成,首轮低温雨雪出现在2月1-4日,降水相态具有多样性,尤其是3日雨雪最为明显,以强降雪及强冻雨为主,导致积雪和积冰快速增长。第二轮低温雨雪出现在5-6日,贵州东部、湖南中北部以冻雨为主,湖北等长江沿线以雨夹雪和降雪为主,积冰得以维持或继续增长。(2)亚洲中高纬度位势高度距平呈西低东高分布,且南支槽活跃,为低温雨雪冰冻天气提供了重要天气背景。南支槽前强盛的西南急流沿锋面爬升形成倾斜上升气流,增强了锋后的降水强度,造成第一轮强低温雨雪天气;而后南支槽减弱,但南支锋区仍维持,中低层急流和地面静止锋均维持,造成了第二轮持续低温雨雪天气。(3)受华南静止锋和云贵静止锋形成及维持的影响,锋后逆温范围宽广,且长江以南地区暖层显著,造成长江南北不同相态的降水。同时长江南北的温湿场在垂直方向上有较大差异,长江以北地区以强降雪为主时,温湿场上表现为深厚的冷湿特征,具有典型的冰相结构;长江以南地区以强冻雨为主时,温湿场上具有“强暖湿-冷湿”特征。(4)2月3-4日长江南北地区均出现快速跃增的雨水、冰水和雪的混合比,形成了强湿雪和强冻雨;长江以南地区低层过冷水3日夜间以小雨滴和大雨滴方式共存5日夜间则是由小雨滴构成。

瑞丽江中游水位变化趋势与河床演变关系分析

瑞丽江河道水资源丰富,河道落差大,适合水电开发,目前已按规划建成多个水电站,认识瑞丽江水位的变化规律和趋势可为瑞丽江水电开发、管理提供依据。本文以干流中游腾龙桥水文站为例,利用Mann-Kendall检验法分析1968—2022年瑞丽江水位变化规律,基于断面实测数据分析瑞丽江河段河床演变规律,并探讨瑞丽江水位变化与河床演变之间的关系。结果表明:1968—2022年瑞丽江年均水位在2004年前呈缓慢上升趋势,2005年后持续下降,经检验为显著下降趋势,至2022年仍处于下降阶段。汛期、枯水期水位自2004年后呈明显下降趋势,同流量枯期水位变幅大于汛期。1968—2022年典型纵横断面表明瑞丽江河床下切严重,下切深度达3.6 m。来水来沙及河床演变是汛期水位变化的主要原因,枯水期水位下降主要原因则为河床下切。

基于MK检验和小波谱分析的赣江上游旱涝变化特征研究

近年来在全球碳排放转型的大背景下,气候变化成为相关学者研究的热点问题。其中全球变暖带来的区域降水变率的不稳定性对社会可持续发展产生了重要影响。因此,为研究长时间尺度下的赣江上游地区环境变化规律,在相关气候要素中,选择旱涝变化作为衡量指标,利用MK检验和小波谱分析方法对近五百年旱涝变化趋势以及周期性特征进行研究。结果表明,赣江上游地区明清以来的近五百年旱涝变化趋势较为明显,总体上涝灾处于增加态势;通过小波谱分析得出,赣江上游地区旱涝演变具有一定的周期性,尤其是不同尺度下的演变周期具有异质性。本研究可以为区域可持续发展研究提供长时间尺度的气候演变规律历史相似型,并为旱涝灾害研究提供基础数据。

MIKE21在淮河中游某码头工程防洪影响分析中的应用

为分析淮河中游某码头建设前后对河道防洪的影响,基于MIKE21构建了码头建设河段工程前后二维水动力模型,对码头工程建设对河道水位、流速等影响情况进行模拟分析,计算结果表明,码头工程建设后,水位最大降低0.21m,流速最大增加0.175m/s,河道主泓流场分布基本稳定,对河道防洪影响较小。同时本文也提出针对所处河道凹湾的码头,工程建设时要做好港池喇叭口位置的岸坡防护措施以及与下游河道岸坡平顺衔接。

基于Sentinel-1A的2016年长江中下游重灾区洪水遥感监测及灾情评估

基于Sentinel-1A雷达成像系统,对2016年5月18日—8月10日长江中下游流域洪水灾害最为严重的区域(115°~117°E,28°~31°N)的整个洪水周期进行了时序动态监测,掌握整个流域的洪水水情状况,并快速提取了洪水淹没范围,对受灾地区的灾情进行评估。据监测结果,整个研究区受灾面积总计达2 096.95 km2,受灾最为严重的区域位于大型湖泊、水库周围地势相对平坦低洼的区域;在各县级行政单元中,安徽省南部的县城受灾最为严重,宿松县受淹面积最大,达290.09 km2,占全县面积的12.12%;在各地表覆被类型中,耕地和居民地受洪水灾害影响最大,占总受淹面积的80.33%,受淹耕地总计947.45 km2,受灾居民地总计76.06 km2,其中,旱地受洪灾影响最严重的区域位于安徽省怀宁县(150.95 km2),占所有受灾旱地面积的22.55%,水田受洪灾影响最为严重的县为安徽省宿松县(90.58 km2),占所有受灾水田面积的32.57%;居民地受洪灾影响最为严重的为安徽省怀宁县(12.85 km2),占所有受灾居民地总面积的16.89%。