SHIFTS OF RAIN BELTS IN EASTERN CHINA AND FLOODS OF THE YANGTZE RIVER BASIN IN 1849

雨带提前进入长江流域并提早撤回、降水异常增多是1849年该地区发生严重洪涝的直接天气原因.本文利用洪涝档案史等资料复原了该年主要的降雨过程和雨带推移过程、长江流域夏季的雨区和降雨强度的时空变化以及洪涝灾害的空间分布.结果表明:1)该年我国东部地区至少有6次主要降雨过程,20次暴雨过程.其中长江流域至少有3个主要连续降雨时段,13次暴雨过程.雨带5月18日～5月30日推进到长江下游地区,8月下旬撤回;2)长江流域夏季雨区主要沿江河分布,整体上有从江南向江北,从下游向中上游逐渐扩展的趋势,同时降雨强度逐渐增大,暴雨区域扩大;3)该年洪涝灾害集中分布在长江中下游沿岸,长江沿岸11个省(市)中有279个县(市)发生洪涝,占当年全部洪涝灾害县(市)的71％,降水异常偏多是发生洪涝的直接原因.     

福建德化霞碧滑坡渗流稳定性模拟分析

降雨入渗导致土体孔隙水压力的增大造成土体有效抗剪强度的降低,进而发生滑坡。本文建立滑坡饱和-非饱和渗流有限元模型,考虑孔隙水压力随时间和空间任意不规则分布,计算特定降雨量、降雨强度、降雨历时不同滞后时段基于渗流场的滑坡稳定性。     

基于统计理论的产流模型

提出了一个基于统计理论的产流模型,该模型考虑了降雨、土壤下渗能力及土壤蓄水容量的空间变异性。假定每个时段的降雨量在空间上可以用概率密度函数或分布函数描述,根据实测降雨资料通过统计拟合优度途径估计各时段降雨的空间概率分布;采用抛物线型函数分别描述土壤下渗能力和土壤蓄水容量的空间分布。按照超渗产流机制计算地表产流量,通过降雨量和土壤下渗能力的联合分布推导得到地表径流量的统计分布,进而得到平均产流量的解析表达式。下渗水量补充土壤含水量,假定满足田间持水量后形成地下径流,其产流量根据下渗量和土壤蓄水容量的空间分配曲线进行计算。以半湿润的黄河支流伊河东湾流域为例,对模型进行了验证和应用,并与新安江模型的结果进行了对比。结果表明,模型对所研究的半湿润区的洪水模拟预报有较好的模拟效果。     

利用雨雪分寸重建福州前汛期雨季起始日期的方法研究

阐述清代福州雨雪分寸记录的特点;并利用福州1961-2010年器测降水记录,分析福州3～7月降水特征,提出辨识福州前汛期雨季开始日期的指标。在此基础上,根据清代福州雨雪分寸记录的内容和形式,分类构建利用雨雪分寸辨识福州前汛期雨季起始日期的方法;依据日降雨分寸、降雨日期和强度、时段的降水日期（或时段起止日期）及降水日（次...     

基于模糊集理论的降雨不确定性传播影响研究

基于模糊集理论,耦合遗传算法,量化分析降雨的量级、空间分布和时程分配产生的不确定性对流量模拟的影响。雨量量级的不确定性使用模糊集概念表示,运用遗传算法对时段雨量在时间上进行随机解集,并通过在各子流域上采用不同的时间解集模式以同时考虑降雨时程分配和空间分布不确定性。应用TOPMODEL对资水流域新宁水文站洪水过程进行模拟研究,结果表明,雨量不确定性的传播对洪水预报的影响处于主导地位,降雨时空分布引起的不确定性对洪水模拟的影响次之。此外,通过对1 h和0.5 h解集结果的比较发现,本文中采用1 h作为模拟的时间步长已可以较充分反映雨量的时间变异性。     

基于Fisher判别算法的山洪灾害临界雨量指标计算

根据临界雨量指标的概念,将模式识别算法引入临界雨量计算中,提出了基于Fisher判别算法的临界雨量计算方法.首先确定特征时段,基于长系列山洪灾情记录将降雨数据分成成灾和非成灾两类,并分别统计特征时段雨量、计算其前期有效降雨,构建山洪灾害各特征时段雨量与前期有效降雨状态空间;建立基于Fisher判别算法的不同特征时段雨量...     

淮河流域极值降雨频率估计时空分布一致性检验和纠正

由于地面雨量站点空间不均及站点资料长度有限、相邻时段和相邻一致区的最优分布函数选择不同,造成降雨频率估计值出现交叉和空间不连续的现象,时空不一致的问题尚没有得到合理的解决。为了获取更加完善合理、时空一致的频率估计值,利用水文气象分区线性矩法计算出的频率估计值,通过误差分摊和二次空间插值及平滑技术对时空分布一致性进行检验和纠正,消除分布曲线的交叉和边界梯度的问题。研究结果表明:通过误差分摊纠正后,消除了交叉异常曲线,各个时段的频率估计值相互制约更加合理;通过空间二次插值纠正后,边界梯度和误差得到明显改善,各站点的频率估计值的经验频率与理论概率更接近,空间分布也更合理。多时段不同重现期下的频率估计值空间分布总体趋势一致,最大值主要分布在淮河流域的东北沂蒙山区,最小值分布在流域的北部平原地区,与站点的实际观测相一致,可为工程设计暴雨和洪水提供基础资料和重要水文依据。     

山东省崩塌、滑坡、泥石流灾害发育现状与趋势分析

山东省崩塌,滑坡,泥石流灾害具区域分布相对集中,形成条件大致相近,周期性变化规律,其诱发因素主要是地震和降雨,本文采用统计法和标准点密度法对灾害的时空分布特征作了分析,并根据地质背景条件及气象周期,地震活动规律预测了灾害的多发部位和多发时段。     

降雨对黄土路基边坡的冲刷规律

针对干旱半干旱地区分布的黄土,利用室内路基模型通过冲刷试验,研究路基降雨冲刷破坏的过程,并利用PFC进行流-固耦合模拟,旨在研究黄土路基遭受水流侵蚀的坡面冲刷规律,找出适用路基抗雨水冲刷稳定性的边坡坡率。路基模型的边坡坡率为1∶0.50、1∶0.70、1∶1.00、1∶1.50、1∶1.75五个等级,模拟的降雨强度按4.0 mm/min、5.0 mm/min、7.0 mm/min、8.5 mm/min、10.0 mm/min五个等级,降雨历时30 min,进行室内降雨冲刷试验和PFC颗粒流模拟试验。获得不同降雨强度和边坡坡率条件下,降雨0 min、1 min、10 min、20 min、30 min的室内降雨冲刷坡面性状图片和PFC软件模拟的颗粒位移量,降雨30 min后坡面冲蚀的泥沙量。结果表明,不同的边坡坡率、降雨强度、降雨历时影响路基边坡坡面的冲刷量,适宜干旱半干旱地区黄土路基边坡坡率为1∶1.50~1∶1.75。     

降水输入时段变化对新疆伊犁地区洪水模拟影响的定量分析研究

为定量分析降雨输入时段对新疆伊犁地区洪水模拟的影响,应用新安江模型,分别分析3组降雨输入时段对模型洪水求解精度的影响。分析结果表明:在静态参数下,随着降雨输入时段的增加,降雨均化作用增强,洪峰和洪量模拟相对误差递增,过程拟合的确定性系数逐步减小,模型模拟精度逐步降低;在动态参数下,降雨输入时段对洪水模拟精度影响逐步减弱,降雨均化作用对模拟精度影响逐步消减。研究成果对于新疆伊犁地区洪水模拟具有重要的参考价值。     

A method for flood hazard mapping based on basin morphometry: application in two catchments in Greece

Basin morphometric parameters play an important role in hydrological processes, as they largely control a catchment’s hydrologic response. Their analysis becomes even more significant when studying runoff reaction to intense rainfall, especially in the case of ungauged, flash flood prone basins. Unit hydrographs are one of the useful tools for estimating runoff when instrumental data are inadequate. In this work, instantaneous unit hydrographs based on the time-area method have been compiled along the drainage networks of two small rural catchments in Greece, situated approximately 25 km northeast of its capital, Athens. The two catchments drained by ephemeral torrents, namely Rapentosa and Charadros, have been subject to flash flooding during the last decades, which caused extensive damages at the local small towns of Marathon and Vranas. Hydrograph compilation in numerous locations along the catchments’ drainage networks directly reflected the runoff conditions across each basin against a given rainfall. This gave a holistic assessment of their hydrologic response, allowing the detection of areas where peak flow rates were elevated and therefore, there was higher flood potential. The resulting flood hazard zonation showed good correlation with locations of damages induced by past flood events, indicating that the method can successfully predict flood hazard spatial distribution. The whole methodology was based on geographic information software due to its excellent capabilities on storing and processing spatial data.     

Assessment of LULC and climate change on the hydrology of Ashti Catchment,India using VIC model

The assessment of land use land cover (LULC) and climate change over the hydrology of a catchment has become inevitable and is an essential aspect to understand the water resources-related problems within the catchment. For large catchments, mesoscale models such as variable infiltration capacity (VIC) model are required for appropriate hydrological assessment. In this study, Ashti Catchment (sub-catchment of Godavari Basin in India) is considered as a case study to evaluate the impacts of LULC changes and rainfall trends on the hydrological variables using VIC model. The land cover data and rainfall trends for 40 years (1971–2010) were used as driving input parameters to simulate the hydrological changes over the Ashti Catchment and the results are compared with observed runoff. The good agreement between observed and simulated streamflows emphasises that the VIC model is able to evaluate the hydrological changes within the major catchment, satisfactorily. Further, the study shows that evapotranspiration is predominantly governed by the vegetation classes. Evapotranspiration is higher for the forest cover as compared to the evapotranspiration for shrubland/grassland, as the trees with deeper roots draws the soil moisture from the deeper soil layers. The results show that the spatial extent of change in rainfall trends is small as compared to the total catchment. The hydrological response of the catchment shows that small changes in monsoon rainfall predominantly contribute to runoff, which results in higher changes in runoff as the potential evapotranspiration within the catchments is achieved. The study also emphasises that the hydrological implications of climate change are not very significant on the Ashti Catchment, during the last 40 years (1971–2010).     

高泉沟流域产流产沙的降水特征因子分析

高泉沟流域属于黄土丘陵沟壑区。运用灰色关联与相关系数分析法,分析影响该流域坡面产流产沙的降水特征因子。结果表明对黄土丘陵沟壑区产生径流贡献最大的因子是降雨量;对土壤侵蚀量贡献最大的因子是降雨量半小时雨强复合因子。因此,降雨量的多少是影响本区产流产沙最关键的因素。     

山区小流域洪水分布模式模拟与危险性评估

流域暴雨山洪过程时空异质性强,准确评估雨洪变化特性和洪水危险性对山洪灾害防治具有重要意义。以7个降雨特征指标和6个洪水特征指标刻画流域场次雨洪特性,采用中国山洪水文模型和洪水频率指标相结合,模拟和评估口前流域洪水过程及其危险性。结果表明：场次洪水洪峰模数、洪峰时间偏度、高脉冲历时占比、涨落洪速率与降雨总量、平均雨量、最大雨强、雨峰位置系数、基尼系数等降雨特征指标显著相关,三场致灾洪水过程的降雨均呈现量级大、强度大、历时短、暴雨中心偏中下游的特点;率定期和验证期的平均径流深相对误差均在9%以内,平均洪峰流量相对误差均在11%以内,平均峰现时间误差均在1.7 h以内,平均Nash-Sutcliffe系数为0.80和0.76;各场次洪水有0.0%～93.3%的河段流量达到一般危险及以上等级,三场致灾洪水过程的危险性等级最高,分别有80.0%、35.0%和1.7%的小流域河段流量达到高危险及以上等级。研究可为山区小流域暴雨洪水危险性评估、灾害响应和复盘等提供技术支撑。     

细沟形成对坡面产流产沙过程的影响

为探明细沟形成条件下不同土壤坡面水沙变化特性,利用室内模拟降雨试验,分析了塿土和黄绵土在细沟发育及已有细沟条件下的水沙过程变化规律。结果表明,塿土产流快,易形成细沟,细沟发育有明显的规律性,在坡面上呈平行状分布,细沟密度与坡度密切相关,细沟存在会延长产流时间;黄绵土产流慢,较难形成细沟,细沟发育随机性大。细沟发育对产流过程没有明显影响,土壤入渗快慢是两种土壤产流过程存在差异的主要原因。细沟发育程度加剧,会使塿土含沙量的增加速度加快,达到稳定含沙量的时间提前,坡面已有细沟只对稳定含沙量有明显影响,细沟密度增加会使稳定含沙量提高;黄绵土含沙量的变化主要取决于细沟发育过程中的随机性,当细沟侵蚀以崩塌作用为主时,含沙量会出现急剧增加,即使雨强较小,也会产生严重的土壤侵蚀。     

Impact of Rainfall Variability on River Hydrology: A Case Study of Southern Western Ghats,India

The Western Ghats plays a pivotal role in determining the hydrological and hydroclimatic regime of Peninsular India. The mountainous catchments of the Ghats are the primary contributors of flow in the rivers that sustains the life and agricultural productivity in the area. Although many studies have been conducted in the past decades to understand long term trends in the meteorological and hydrological variables of major river basins, not much attention have been made to unfold the relationship existing among rainfall and river hydrology of natural drainages on either side of the Western Ghats which host one of the unique biodiversity hotspots across the world. Therefore, an attempt has been made in this paper to examine the short term (last three decades) changes in the rainfall pattern and its influence on the hydrological characteristics of some of the important rivers draining the southern Western Ghats as a case study. The short term, annual and seasonal trends in the rainfall, and its variability and discharge were analyzed using Mann-Kendall test and Sen’s estimator of slope. The study showed a decreasing trend in rainfall in the southwest monsoon while a reverse trend is noticed in northeast monsoon. Correspondingly, the discharge of the west and east flowing rivers also showed a declining trend in the southwest monsoon season. The runoff coefficient also followed the trends in the discharge. The runoff coefficient of the Periyar river showed a decreasing trend, whereas the Cauvery river exhibited an increasing trend. A high-resolution analysis of rainfall data revealed that the number of moderate rainfall events showed a decreasing trend throughout the southern Western Ghats, whereas the high intensity rainfall events showed an opposite trend. The decline in groundwater level in the areas which recorded an increase in high intensity rainfall events and decrease in moderate rainfall events showed that the groundwater recharge process is significantly affected by changes in the rainfall pattern of the area.     

Sizing first flush pollutant loading of stormwater runoff in tropical urban catchments

This study aimed at investigating the first flush phenomenon from residential, commercial and industrial catchments. Stormwater was grab sampled and the flow rate was measured during 52 storm events. The dimensionless cumulative pollutant mass and runoff volume were used to determine the runoff volume needed to transport 50 and 80 % of total pollutant mass. Almost all the constituents did not satisfy this first flush definition except for total suspended solids (TSS) in the commercial catchment. The averages first runoff volume required to remove 50 and 80 % of the total pollutant mass were 37 and 67, 35 and 65, and 36 and 64 % for the residential, commercial and industrial catchments, respectively. It seemed that less runoff is required to transport the same amount of pollutant loadings in tropical urban catchments than in temperate regions. BOD, COD, NH₃-N, SRP and TP consistently showed strong first flush effects in all catchments. The first flush strengths of TSS, BOD, COD, NH₃-N and TP in the commercial catchment were strongly correlated with total rainfall, rainfall duration, max 5 min intensity, runoff volume and peak flow, but not with antecedent dry days. Management of the first 10 mm runoff depth would be able to capture about half of the total pollutant mass in stormwater runoff that would otherwise goes to drains.     

黄土边坡降雨侵蚀特征的物理模拟试验研究

黄土边坡的侵蚀破坏是引起黄土地区公路边坡自然灾害的主要诱因。通过建立室内边坡降雨冲刷物理模型, 进行黄土边坡侵蚀破坏的模拟试验, 再现边坡溅蚀、片蚀、沟蚀、坍塌的基本破坏过程, 并对坡面降雨冲刷的演变过程和侵蚀机理进行了细致的描述和分析。试验表明:在一定的降雨雨强下, 径流TSS(携砂能力)和单位面积侵蚀泥沙量随着试验坡度的增加逐渐增加, 而径流总量、侵蚀干泥沙量随着坡度的增加而相应变小。同时, 黄土边坡侵蚀冲刷过程中的主要侵蚀能力参数如坡面径流总量、汇流干泥沙量、侵蚀干泥沙量等与降雨雨强之间存在相应的关系。     

七大流域水文特性分析

我国东西和南北方向地理跨度大,水文特性差异明显。从气候特征、降雨和径流、暴雨和洪水等方面,分析七大流域的水文特性,总结降雨和径流在上下游、干支流等空间上以及年内和年际等时间上的分布规律,并分析暴雨和洪水在成因、发生时间、空间分布、过程等方面的规律,为径流和洪水成果计算提供了基础,也为水文成果的合理性检验提供了参考。     

人工集水面临界产流降雨量确定实验研究

通过在中国科学院寒区旱区环境与工程研究所皋兰生态农业试验站1998-1999年的降雨-径流观测实验,利用直线回归模型确定包括自然集水面在内的9种人工集水面的临界产流降雨量值(降雨阀值)。结果表明:在不受前期降雨影响下,自然黄土坡面、清除杂草自然黄土坡面和粘土夯实集水面的临界产流降雨量分别为8.5mm,8.0mm和4.1mm。在受前期降雨影响下,其临界产流降雨量分别为6.0mm,5.0mm和1.9mm。塑料膜、油毡、沥青和混凝土处理集水面的产流过程受降雨量和降雨强度的影响小,平均状态下其临界产流降雨量为0.1～1.5mm。塑料膜、油毡、沥青、塑料+小砾石和塑料+大砾石集水面的临界产流降雨量分别为0.13mm,0.21mm,0.17mm,0.98mm和0.85mm。混凝土集水面在干燥情况下的临界产流降雨量为1.48mm,在不干燥情况下的临界产流降雨量为1.16mm。