长江亮出生态红牌

从去年11月三峡工程进行大江截流以来,这一年可以说成了中国的长江年。人们庆贺“腰斩长江”的欢呼声犹在耳际,长江便以洪水的形式发难了。自今年6月中旬至8月下旬,流域范围内的3次持续强降雨过程,在中下游干流形成了连续7次洪峰。数百万军民在千里长堤上与洪水拼死搏斗了两个多月。长江的水情日夜牵动着全国的视听。从世界屋脊到东海之滨,万里长江跨越中国地势的三大阶梯,在华夏大地上不舍昼夜川流不息。无论长度、流量、流域面积、人口和经济价值,还是历史与文明意义,长江都可以说是世界上最伟大的河流。说起百年长江,人们也许大…     

洞庭湖区水患成因及防治对策

洞庭湖区位于湖南省北部,包括益阳、常德、岳阳、长沙４市下辖的２９个县（市、区）和１５个国营农场。洞庭湖承纳湘、资、沉、澧四水,以下简称“四水”,集水面积２６万平方公里,长江干流枝江段以上集水面积１０４万平方公里,总计水面积达１３０万平方公里,分别为鄱阳湖和太湖的８倍、２６倍。年平均径流量３１２６亿立方米,分别为番阳湖和太湖的２倍、４６倍。多年来平均汛期（５月至１０月）入湖水量占年径流量总量的７５％,其中９２％来自长江。洞庭湖消纳长江洪水的３０％至４０％,使长江无数次洪患化险为夷,是调蓄长江洪水的…     

完善我国森林立法势在必行

通过对1998年长江、嫩江特大洪水的反思,指出了目前森林立法中存在的种种弊端,从而提出了完善我国森林立法的建议。     

垃圾围困葛洲坝

自6月下旬开始,长江上游及长江三峡库区普降大雨。目前,由洪水带来的各种垃圾聚集漂浮在葛洲坝上游江面,已严重威胁葛洲坝电厂机组以及船闸运行安全。据葛洲坝电厂负责人介绍,这些漂浮垃圾,给电厂造成的最大危害就是磨蚀水轮机叶片,妨碍发电机正常运行,以往甚至出现过发电机组被迫停机的情况。多年来,葛洲坝电厂虽投入大量资金,却始终不能根治。而当洪水退去时,垃圾、污水、淤泥等又极易滞留,造成严重的环境问题。有资料显示,每年汛期,长江干流漂浮物量为10～20万立方米,现在,这些以往困扰葛洲坝电站的垃圾漂浮带,已经开始向长江三峡大坝靠…     

青海：各拉丹冬冰川呈退缩趋势

据悉，受全球气候变暖的影响，备拉丹冬地区冰川总体呈明显波动退缩趋势。各拉丹冬地区是长江源头主要水源补给区，冰川的不断退缩将使得河流的季节性洪水和总体径流量减少，直接影响淡水资源的供给，对长江上游地区水资源状况、区域生态环境及经济社会发展将产生不利影响。     

长江崩滑忧思录

前年七八月间,记者就长江流域的滑坡、崩岸、泥石流。三害”频频发生事件进行过披露报道。两年后的今天．崩岸及滑坡频率仍在加大。今年长江过足进入汛期,而中下游的崩岸、坍塌．上游地区的频繁山体滑坡也呈现出早发和日趋严重的趋势。入春早汛忧心忡忡去冬今春以来,长江中下游及其以南地区气候异常,多数地区大雨、暴雨频降或阴雨连绵。长江干流的水位普遍达到了历史同期最高或者次高水平,湘江、赣江、信江及杭嘉湖地区都发生了洪水．衡阳、珠洲、长沙都出现了超警戒水位2米多的洪峰。l月ZI日,武汉关水位出现了18．93米的超常水位。…     

长江洪涝的警示

1998年夏天,一个令中国人民难忘的盛夏。中国大地上洪水肆虐,特别是长江,发生全流域的特大水灾,给沿岸各省区乃至全国带来的直接和间接损失难以估计。在军民团结一致,中华民族万众一心排除各种险情,制服洪魔,夺取抗洪抢险胜利的同时,上至国家领导,下到平民百姓,都不禁要发出这样的疑问：哺育中华民族的母亲河为什么会向自己的儿女如此示威？长江怎么了？是不是我们忽视了她？是不是我们虐待了她？中国因其地域辽阔,南北跨度大,洪涝灾害几乎年年有之,但今年水位长时间居高不下,长时间超警戒水位及历史最高水位。洪涝如此之凶,…     

长江水灾与长江流域生态破坏有直接关系

今年,我国遭受了历史上罕见的特大洪涝灾害,特别是长江,发生了全流域的大洪水,使国民经济和人民生活受到了严重影响。大洪水引起7人们的深刻反思,诸多的专家学者、有识之士在探究这次大洪水发生的原因后,认为这场洪涝灾害与流域生态破坏有直接关系。本刊为配合对这场洪涝灾害成因及其他问题的讨论,特开辟《洪灾专稿》临时栏目,以便集中、深入地对这一问题展开探讨和研究。今年入夏以来,超常雨量顺泄我国部分地区,长江、嫩江、松花江发生的特大洪水为近年来所罕见。人们在奋力抗洪的同时,不禁要问：天怎么了？有关专家对长江流域…     

长江上拉响了警报

题记：中国俗称滑坡为“走山”，称大规模的滑坡、崩坍为“山崩”，其主要发生在地质薄弱的断层带、植被受破坏的斜坡以及设计不周的工程点。本世纪最大的滑坡事件发生在中国海原（1920年），这次地震中丧生23．4万人，实际上大部分死于滑坡。1981年，四川盆地的洪水引发了6万多处滑坡和泥石流，灾民达北多万人。以往主要集中在我国西南山区和黄土高原的山崩、滑坡。近10年来．由于种种原因，在长江上游日渐频繁．近几年且有随大江东去之势。长江中下游的最新崩岸记录1996年，入汛之前，长江中下游频频发生滑坡、崩岸等灾情。有北门口崩岸一…     

2013年洪水灾害后大伙房水库的水质变化情况分析

主要论述了2013年大伙房水库的水质现状及洪水灾害后大伙房水库的水质变化情况,并与非洪水发生年份(2010年至2012年)进行比较,进一步确定总磷是洪水之后水质变化的主要因子,简要分析了洪水灾害后影响水质的污染物来源。     

FLOOD DAMAGES IN CHANGING FLOOD PLAINS: A FORENSIC‐HYDROLOGIC CASE STUDY1

ABSTRACT: Hydraulic modification of flood plains by human activity is the primary cause of rising flood damages throughout the world. As flood‐plain hydraulic roughness increases, so does the water level for a fixed flow rate. This raises the flood damage associated with a flood of given return period, and thus, magnifies the flood risk. This article presents an approach that integrates climatic, hydrologic, and hydraulic principles and presents models to discern the probable causes of flood damage in a basin that undergoes flood‐plain development. The article documents key factors that govern flood damage and presents a case study that illustrates the principles of forensic hydrology in an impacted flood plain. The study demonstrates flood level rise caused by hydraulic alteration of a flood plain between 1969 and 1995 and apportioned the increased water level among agricultural and structural factors located in the study area.     

DEVELOPMENT OF A GIS‐BASED FLOOD INFORMATION SYSTEM FOR FLOODPLAIN MODELING AND DAMAGE CALCULATION1

ABSTRACT: This work presents a flexible system called GIS‐based Flood Information System (GFIS) for floodplain modeling, flood damages calculation, and flood information support. It includes two major components, namely floodplain modeling and custom designed modules. Model parameters and input data are gathered, reviewed, and compiled using custom designed modules. Through these modules, it is possible for GFIS to control the process of flood‐plain modeling, presentation of simulation results, and calculation of flood damages. Empirical stage‐damage curves are used to calculate the flood damages. These curves were generated from stage‐damage surveys of anthropogenic structures, crops, etc., in the coastal region of a frequently flooded area in Chia‐I County, Taiwan. The average annual flood damages are calculated with exceedance probability and flood damages for the designed rainfalls of 2, 5, 10, 25, 50, 100, and 200 year recurrence intervals with a duration of 24 hours. The average annual flood depth in this study area can also be calculated using the same method. The primary advantages of GFIS are its ability to accurately predict the locations of flood area, depth, and duration; calculate flood damages in the floodplain; and compare the reduction of flood damages for flood mitigation plans.     

FLOOD CONTROL RESERVOIR OPERATIONS UNDER ENVIRONMENTAL RESTRAINTS1

ABSTRACT: A flood control reservoir protects valuable developments on the downstream flood plain by storing flood waters and releasing them at a rate that will reduce the downstream damage. The water surface level of the flood pool behind the dam can fluctuate considerably during the occurrence of a large magnitude flood causing the inundation of trees, low vegetation, and water based recreation facilities located in those areas of the flood pool area that are normally well above the water level. The amount of damage that will occur in the upper levels of the flood storage area will depend on the depth and duration of the inundation that occurs. This, in turn, is directly related to the operating policy for the reservoir. A dynamic programming optimization model of flood control reservoir operation is presented. This model determines the reservoir operating schedule that minimizes downstream flood damages. Various constraints are added to the model to account for the environmental impacts of long periods of flood storage.     

Impacts of Human Behavioral Heterogeneity on the Benefits of Probabilistic Flood Warnings: An Agent‐Based Modeling Framework

Flood forecasts and warnings are intended to reduce flood‐related property damages and loss of human life. Considerable research has improved flood forecasting accuracy (e.g., more accurate prediction of the occurrence of flood events) and lead time. However, the delivery of improved forecast information alone is not necessarily sufficient to reduce flood damage and loss of life, as people have varying responses and reactions to flood warnings. This study develops an agent‐based modeling framework that evaluates the impacts of heterogeneity in human behaviors (i.e., variation in behaviors in response to flood warnings), as well as residential density, on the benefits of flood warnings. The framework is coupled with a traffic model to simulate evacuation processes within a road network under various flood warning scenarios. The results show the marginal benefit associated with providing better flood warnings is significantly constrained if people behave in a more risk‐tolerant manner, especially in high‐density residential areas. The results also show significant impacts of human behavioral heterogeneity on the benefits of flood warnings, and thus stress the importance of considering human behavioral heterogeneity in simulating flood warning‐response systems. Further study is suggested to more accurately model human responses and behavioral heterogeneity, as well as to include more attributes of residential areas to estimate and improve the benefits of flood warnings.     

ANALYSIS OF UNCERTAINTY IN FLOOD PLAIN MAPPING1

ABSTRACT: Components contributing to uncertainty in the location of the flood plain fringe of a mapped flood plain are identified and examined to determine their relative importance. First-order uncertainty analysis is used to provide a procedure for quantifying the magnitude of uncertainty in the location of the flood plain fringe. Application of the procedure indicated that one standard deviation of uncertainty in flood plain inundation width was about one third of the mean computed inundation width for several flood population-flood geometry combinations. Suggested mapping criteria, which directly incorporate uncertainty estimates, are given. While these criteria are more suitable for use in developing areas than in flood plains that have had extensive development, the analysis procedure can be used to accommodate property owners who challenge the validity of estimated flood fringe boundaries. Use of uncertainty analysis in flood plain mapping should enhance the credibility of the final plan.     

A Faster and Economical Approach to Floodplain Mapping Using Soil Information

Flood inundation maps play a key role in assessment and mitigation of potential flood hazards. However, owing to high costs associated with the conventional flood mapping methods, many communities in the United States lack flood inundation maps. The objective of this study is to develop and examine an economical alternative approach to floodplain mapping using widely available soil survey geographic (SSURGO) database. In this study, floodplain maps are developed for the entire state of Indiana, and some counties in Minnesota, Wisconsin, and Washington states by identifying flood‐prone soil map units based on their attributes. For validation, the flood extents obtained from SSURGO database are compared with the extents from other floodplain maps such as the Federal Emergency Management Agency issued flood insurance rate maps (FIRMs), flood extents observed during past floods, and flood maps derived using digital elevation models. In general, SSURGO‐based floodplain maps (SFMs) are largely in agreement with other flood inundation maps. Specifically, the floodplain extents from SFMs cover 78‐95% area compared to FIRMs and observed flood extents. Thus, albeit with a slight loss in accuracy, the SSURGO approach offers an economical and fast alternative for floodplain mapping. In particular, it has potentially high utility in areas where no detailed flood studies have been conducted.     

FLOOD FREQUENCY ANALYSIS FOR EVALUATING WATERSHED CONDITIONS WITh RAINFALL-RUNOFF MODELS1

ABSTRACT: Many rainfall-runoff modeling studies compare flood quantiles for different land-use and/or flood mitigation scenarios. However, when flood quantiles are estimated using conventional statistical methods, comparisons may be misleading because the estimates often misrepresent the quantile relationship between scenarios. An alternate statistical procedure is proposed, in which rainfall-runoff modeling is used to evaluate an approximate relationship between flood quantiles for different scenarios. Monte Carlo experiments show that the proposed method produces flood quantile estimates that better reflect the differences between scenarios. The ratio between quantiles for different scenarios is more accurate, so comparisons of the scenarios using flood quantiles are more reliable.     

USE OF HISTORIC FLOOD INFORMATION IN ESTIMATING FLOOD PEAKS ON UNGAGED WATERSHEDS1

Regional procedures to estimate flood magnitudes for ungaged watersheds typically ignore available site-specific historic flood information such as high water marks and the corresponding flow estimates, otherwise referred to as limited site-specific historic (LSSH) flood data. A procedure to construct flood frequency curves on the basis of LSSH flood observations is presented. Simple inverse variance weighting is employed to systematically combine flood estimates obtained from the LSSH data base with those from a regional procedure to obtain improved estimtes of flood peaks on the ungaged watershed. For the region studied, the variance weighted estimates of flow had a lower logarithmic standard error than either the regional or the LSSH flow estimates, when compared to the estimates determined by three standard distributions for gaged watersheds investigated in the development of the methodology. Use of the simple inverse variance weighting procedure is recommended when “reliable” estimates of LSSH floods for the ungaged site are available.     

Flood control failure: San Lorenzo River,California

The San Lorenzo River on the central California coast was the site of a major US Army Corps of Engineers flood control project in 1959. By excavating the channel below its natural grade and constructing levees, the capacity of the river was increased in order to contain approximately the 100 year flood. Production and transport of large volumes of sediment from the river's urbanizing watershed has filled the flood control project with sand and silt. The natural gradient has been re-established, and flood protection has been reduced to containment of perhaps the 30 year flood. In order for the City of Santa Cruz, which is situated on the flood plain, to be protected from future flooding,it must either initiate an expensive annual dredging program, or replan and rebuild the inadequately designed flood control channel. It has become clear, here and elsewhere, that the problem of flooding cannot simply be resolved by engineering. Large flood control projects provide a false sense of security and commonly produce unexpected channel changes.     

FLOOD HAZARD STUDIES IN THE MISSISSIPPI RIVER BASIN USING REMOTE SENSING1

ABSTRACT. The Spring 1973 Mississippi River flood was investigated using remotely sensed data from ERTS-1. Both manual and automatic analyses of the data indicate that ERTS-I is extremely useful as a regional tool for flood management. Quantitative estimates of area flooded were made in St. Charles County, Missouri and Arkansas. Flood hazard mapping was conducted in three study areas along the Mississippi River using pre-flood ERTS-1 imagery enlarged to 1:250,000 and 1:100,000 scale. The flood prone areas delineated on these maps correspond to areas that would be inundated by significant flooding (approximately the 100 year flood). The flood prone area boundaries were generally in agreement with flood hazard maps produced by the U. S. Army Corps of Engineers and U. S. Geological Survey although the latter are somewhat more detailed because of their larger scale. Initial results indicate that ERTS-1 digital mapping of flood prone areas can be performed at 1:62,500 which is comparable to some conventional flood hazard map scales.