Radial growth response of Hedera helix to hydrological changes and climatic variability in the Rhine floodplain

This paper presents a dendrochronological study of Common Ivy in alluvial environment. Our objective was to analyse the response of ivy plants to hydrological and climatic variations. The study was carried out in three forests: Rhinau, which is regularly flooded; Erstein, where floods were eliminated with the canalization of the Rhine River in 1967 and Heiteren, an upland forest. Multivariate models performed for each forest showed that the response of ivy to temperature, precipitation and water table level depended on the hydrological history of the site. In the flooded forest of Rhinau, ground water depth in June and July, that is at the time when floods usually occur, was one of the main factors stimulating growth while in Erstein, rises of the ground water levels stimulated growth only when they occurred in winter, that is when the water table is normally the lowest in the year. In the driest forest of Heiteren, growth was stimulated by hot summer temperatures coupled with rainfall from May to July. In the two riparian forests ivy displayed a positive response to increasing temperatures in February and March. The ability to take advantage of early temperature increases may be a particularly important aspect of ivy ecology in deciduous forests. Copyright © 2008 John Wiley & Sons, Ltd.     

嫩江下游洪水演进及对洪泛区植被影响分析

为揭示嫩江下游洪水演进规律及对洪泛区植被的影响,利用MIKE FLOOD建立了嫩江江桥—大赉河段的一、二维水动力耦合模型,选取1998年与2013年汛期实测资料对河段糙率进行了率定与验证,并模拟了典型河段4种不同重现期洪水的演进过程。在此基础上基于2000—2019年MODIS卫星的MOD13Q1数据集,获取了不同洪水频率淹没范围内的植被指数(NDVI、EVI),评估了嫩江下游不同重现期洪水扰动对植被的影响。结果表明:模型在率定期与验证期的模拟效果符合甲级预报精度,模型模拟精度较高;不同重现期内的植被指数具有较强的季节变化规律,且洪水对植被具有明显的破坏作用,但这种破坏作用在嫩江流域周期性相对较短,表明该地区植被的可恢复性较强;同时受洪水频繁淹没程度影响,不同重现期的植被指数符合中度干扰假说。     

The flood of the century on the River Oder: effects on the 0+ fish community and implications for floodplain restoration

In summer 1997, the flood of the century occurred on the River Oder in the Czech Republic, Poland and Germany. Effects of the summer flood on the 0+ fish community were evaluated at the Lower Oder in the Polish–German National Park. Fish were collected from different mesohabitats before the flood, at rising water levels and after the flood using Point Abundance Sampling by electrofishing. Flooding caused changes in local 0+ fish assemblages and partly affected the physical habitat structure. Two sandbars were formed by breaches in the dike system, replacing the former uniform river embankments. Under post‐flood conditions, diversity was increased in nearly all mesohabitats. ‘Wash‐out’ of 0+ fish was highest in poorly structured mesohabitats. Effects of the summer flood on eurytopic species were the most pronounced. We suggest that the progeny of rheophilic species were affected to a lesser extent by flooding because of their adaptation to variable flow conditions. Furthermore, rheophilic 0+ fish were able to colonize the newly created mesohabitats and, thus, benefited from the increased habitat heterogeneity after the flood. In this context, implications for floodplain restoration are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of flooding regime upon the decomposition of Eichhornia azurea (Sw.) Kunth measured on a tropical,flow‐regulated floodplain (Paraná River,Brazil)

Decomposition of macrophytes is an important process in river‐floodplain systems, especially in the Upper Paraná River floodplain, given that this ecosystem receives high inputs of detritus from this vegetation. Release of nutrients by decomposition is essential in this floodplain because it is located downstream from a reservoir chain where nutrients are being trapped. Water level fluctuations are considered one of the most important aspects that affect macrophyte decomposition. Anthropogenic alterations, such as the control of flooding regimes, observed in this floodplain, could change the dynamic of this process. To evaluate the influence of the hydrological cycle upon the decomposition of Eichhornia azurea (an aquatic macrophyte that has high biomass values in this ecosystem), litter bags with senescent leaves and petioles of this plant were submitted to four different flooding treatments, which differed in time of flooding and exposure to dry conditions. The decomposition rates and the detritus chemical composition (nitrogen and phosphorus concentrations) were measured over 113 days. There were significant effects of the flooding treatments and time upon all parameters. The materials that decomposed with flood conditions showed the greatest decomposition rates. The quality of the detritus seems to be highly linked with the flooding regime, showing highest releases of phosphorus in the submerged treatments. It was shown that floods, even the short duration ones, increase the decomposition velocity and the nutrient cycling relative to dry conditions. Thus, investigations that assess the nutrient budgets on the Upper Paraná River floodplain and the role of nutrients in its productivity should consider the detritus compartment and the effects of flood regimes upon its dynamics. Copyright © 2006 John Wiley & Sons, Ltd.     

Impact of a 100‐year flood on vegetation,benthic invertebrates,riparian fauna and large woody debris standing stock in an alpine floodplain

This paper investigates the impact of a 100‐year flood in May 1999 on community composition and large woody debris standing stock in an alpine floodplain (Isar, Germany). Detailed pre‐flood data sampled from 1993 to 1998 are compared with the situation directly after the flood. In those parts of the Isar floodplain mainly covered with pioneer vegetation prior to flooding, the coverage of unvegetated gravel bars increased by 22% following the flood. However, the flood did not remove larger amounts of older successional vegetation stages (willow thickets, floodplain forest). No significant changes in the benthic invertebrate fauna were recorded. The lowest densities of riparian ground beetles (Carabidae) within the study were recorded one month after the flood. Two months later, the ground beetle densities increased to the highest values ever recorded, indicating the ground beetle's high potential for recolonization. These results highlight the degree of resilience of both the aquatic and the riparian invertebrate fauna. The flood also caused a significant increase in large woody debris standing stock; in one section the number of logs increased tenfold and the volume increased by a factor of 20, leading to the assumption that most woody debris in alluvial flood‐plains is provided by catastrophic events. Copyright © 2004 John Wiley & Sons, Ltd.     

梅溪流域城镇化进程对山前平原区洪涝过程的影响

为探究城镇化进程引起土地利用类型变化对山前平原区洪涝过程的影响,以梅溪流域下游平原区的洪濑镇为例,分析了2002—2018年梅溪流域上游山区和下游平原区的土地利用类型变化,并基于多情景数值模拟,研究了流域尺度内土地利用类型变化对山前平原区洪涝过程和地表淹没状况的影响。结果表明：随着梅溪流域耕地和林地面积减少、城镇建设用地增加,上游山区的径流系数和峰值流量均增大,下游山前平原区的淹没状况更加严重;上游山区的城镇建设用地增加使山区骤发洪水峰值流量增大、峰现时间提前,主要影响地表平均最大淹没水深和平均峰现时间;下游平原区的城镇建设用地增加使内涝发生的时间提前,主要影响地表平均淹没历时。     

Influence of the flood regime on the reproduction of fish species with different reproductive strategies in the Cuiabá River,Upper Pantanal,Brazil

This study evaluated the influence of the flood regime of the Cuiabá River on the reproductive dynamics of fish species with different reproductive strategies. Sampling was carried out at ten sites in the basin, between March 2000 and April 2004. The reproductive strategies evaluated were long‐distance migrant (LM), short‐distance migrant (SM), sedentary with parental care (PC) and sedentary or SM with internal fertilization (IF). Period, duration and intensity of floods were the flooding attributes considered. Duration and time of spawning were evaluated using the index of reproductive activity (IRA), and inferences concerning reproductive allocation were based on the analysis of gonad weight. Reproductive success was evaluated based on the annual catch of young‐of‐the‐year of each species. Reproductive dynamics and flood regime were closely correlated; the reproductive peaks of fishes using all four strategies always preceded flood peaks. Intense floods favoured gonadal development of LM and PC, but were less important for IF. In relation to juvenile survival, the occurrence of floods appeared to be crucial for the strategies of LM, PC and IF, because such floods increased fish survival in the period of initial development. In contrast, SM appeared to be less dependent on floods for reproduction. These results indicate that, except for SM, floods have an important role in the recruitment of species using other reproductive strategies, and influence spawning success as well as juvenile survival. Copyright © 2008 John Wiley & Sons, Ltd.     

黄河凌汛和伏汛引水对库布其沙漠北缘生态格局及其耗水变化影响研究

为减轻黄河几字弯防凌防汛压力,内蒙古将凌汛和伏汛现水引入了库布其沙漠北缘,使下垫面生态格局发生变化的同时,区域水文循环过程也受到影响,尤其是下垫面耗水过程。为深入明晰库布其沙漠北缘生态格局及其耗水变化的驱动内因,本文利用遥感影像分析了引水前后生态格局演变特征,基于遥感蒸散发理论详细阐明区域耗水时空变化机制,并评价变化背景下气象因子(气温、降水、湿度与风速)与区域耗水的相关程度。结果表明：①黄河凌汛和伏汛水显著影响了库布其沙漠北缘生态格局,引水后沙地面积占比由72.5%缩至15.8%,湖泊、湿地占比从零增至27.5%、4.5%;②基于METRIC模型与Dalton蒸发理论计算陆面蒸散发和水面蒸发的相对误差分别为9.2%、9.3%,区域耗水结果具有较高可信度,引水前(2013年)、引水初(2016年)、引水后(2020年)作物生长季(4—10月)蒸散发为156.22、231.12和528.58 mm,凌汛和伏汛引水对区域耗水影响持续增强;③黄河凌汛和伏汛引水改变了蒸散发与气象因子(气温、降水、风速、湿度)相关关系,蒸散发与气温、湿度的正相关性持续增大,呈正相关关系的区域占比由引水前73%、28%分别增至95%、76%。     

丹江口水利枢纽对汉江中下游防洪影响分析

1968年建成的汉江丹江口水利枢纽在防洪保护下游人民生命财产安全、维护社会稳定等方面产生显著社会效益的同时，还带来了巨大的经济效益。截至1990年，仅防洪、发电、灌溉三项效益已达101亿元，相当于原投资的8，5倍。尤其是根据分期设计洪水拟定防洪调度，又可为枢纽年增加发电量2．44亿kw·h。在分析研究流域暴雨洪水特性的基础上，论述枢纽对汉江中下游防洪的影响。根据流域特性，在保证下游防洪安全前提下制定合理的分期调度规程，减少弃水，增加水头，可显著提高枢纽的综合效益。     

黄河下游滩区享受蓄滞洪区运用政策补偿可行性研究

2000年国家出台了《蓄滞洪区运用补偿暂行办法》,对处理蓄滞洪区运用后的群众受灾补偿和灾后重建发挥了很好的作用。黄河下游滩区具有明显的蓄滞洪区的性质和功能,几十年来,滩区的蓄滞洪功能的发挥为黄河安澜起到了巨大的作用。依照《办法》,有必要对黄河下游滩区享受蓄滞洪区政策补偿的可行性进行研究。     

黄河中游地区淤地坝减洪减沙及减蚀作用研究

本文对黄河中游河龙区间及泾河、北洛河、渭河流域淤地坝的减洪减沙及减蚀作用进行了深入地分析和研究。提出了淤地坝减洪量、拦泥量和减蚀量的计算方法；对淤地坝的减蚀量进行了分析和计算。分析研究结果表明：作为多沙粗沙区核心地区的河龙区间，1970～1996年淤地坝减洪减沙量分别占水土保持措施减洪减沙总量的59.3%和64.7%，其减洪减沙作用十分明显。1970～1996年，河龙区间及泾河、北洛河、渭河流域淤地坝年均减沙达1.138亿t，可为黄河下游减少淤积0.285亿t；可减少冲沙用水22.8亿m3；节约清淤费用85.5亿元。淤地坝建设的生态效益、社会效益和经济效益十分显著。为此，建议黄河中游黄土高原地区应以淤地坝建设为重点，全面推进水土保持生态建设。     

论黄河下游滩区生产堤对防洪的影响

黄河下游修建的生产堤，对保护滩区农业生产曾起到过积极的作用，但由于生产堤的存在，缩窄了河道的过洪断面，削弱了河道滞洪排洪能力，使同流量洪水水位抬高，洪峰流量沿程衰减量变小，洪水传播的时间缩短，严重影响了下游水文报的精度，给防洪决策带来十分不利的影响，因此，必须彻底破除黄河下游滩区存在的生产堤。     

黄河下游宽滩区滞洪沉沙功能与减灾效应二维评价模型及其应用

黄河下游宽滩区既是大洪水行洪滞洪沉沙的通道,又是滩区群众赖以生存和发展的家园,如何合理运用宽滩区是长期备受关注和争议的话题。本文在水沙统筹、空间统筹和时间统筹原则的指导下,建立了黄河下游宽滩区滞洪沉沙功能与减灾效应二维评价指标体系,构建了基于Pareto最优解的黄河下游宽滩区滞洪沉沙功能与减灾效应二维评价模型,利用1958、1982、1992和1996年4场洪水实测资料,对该模型的合理性进行了验证。应用上述模型对黄河下游宽滩区不同运用方式的12组二维数学模型计算方案进行了评价,结果表明,洪水量级对减灾效应影响显著;相同洪水条件下设防护堤并控制闸门运用(有闸)或分区运用(5滩、10滩)方案能在滞洪沉沙功能和减灾效应之间取得更好的平衡,可作为未来滩区优化运用的决策参考。     

黄河洛河渭河在三门峡库区洪水遭遇预测方法的探讨

本文采用自然正交函数分析法对黄河、洛河、渭河洪水在三门峡库区遭遇进行分析探讨,得出只要预测未来时间系数就可预测未来洪水相遇的可能性大小,并得到了比较可靠的结果,在三门峡库区及其它河流的洪水遭遇分析具有重要的实用价值.     

上海苏州河市区段防汛墙的加固改造

苏州河市区段两岸的防汛墙建设年代久远,建设标准低,存在巨大的安全隐患,迫切需要对现有防汛墙进行加固改造。在分析水文、地质和防汛墙现状的基础上提出加固改造方案,分别采取拆除新建型、墙前加固型、墙后加固型和骑跨式加固型等型式,根据地形选取不同的断面,结合苏州河沿线景观规划,以保证防汛安全为基础,兼顾生态环境和亲水平台建设,形成沿河公共开放空间。     

地面沉降对永定河中下游防洪安全影响分析

地面沉降是我国平原地区的重要地质灾害之一,严重的地面沉降使堤防、闸等防洪工程设施同步下沉。永定河流域地面沉降主要分布在中下游地区,该地区的地面沉降降低了永定河流域防洪工程的防洪、防潮标准,削弱了防灾功能,直接影响天津市和河北省广大地区的防洪安全。为分析地面沉降对永定河系行洪安全影响,本文通过对不同时期测量基准点资料及地形图资料进行比对,分析永定河中下游地区沉降趋势,并采用一、二维嵌套的非恒定流洪水演进数学模型,对永定河泛区行洪能力进行复核。     

福州地区大学新校区防洪排涝体系综合运用分析

福州地区大学新校区防洪排涝体系基本建成,该体系不仅能保证防洪排涝安全,而且可改善水环境。本文就该体系的综合运用从防洪、排涝以及生态景观用水等三个方面进行了分析,并提岀了几点建议,以期充分发挥其综合效益。     

黄河中游水沙频率关系研究

扼要指出进行黄河中游水沙频率关系研究的必要性,并通过对黄河中游部分连续泥沙观测序列的独立同分布性的检验,验证了建立黄河中游泥沙频率曲线的可行性以及泥沙序列对P-Ⅲ型分布曲线的适应性。在此基础上建立了黄河中游水沙序列的理论频率曲线,分析了黄河中游的水沙频率之间的关系,给出了一定泥沙频率条件下所对应的洪水发生的频率范围,对年径流量和输沙量的频率组合进行了量化,对水沙丰枯组合进行了确定,最后提出了有待于进一步研究的问题。     

黄河调水调沙对焦作河段的影响及防汛对策

黄河调水调沙在加大下游河道排洪能力的同时,也使焦作河段河道受到冲刷,河道工程的出险概率增加,给防汛工作带来了新的问题。在强化执法、增强防汛意识的基础上,应采取完善河道工程规划,提高领导决策能力,加强防汛队伍建设,应用新技术、新材料、新工艺等一系列措施,保证河道行洪安全。