CHARACTERISTICS OF EXTREME PRECIPITATION1

ABSTRACT: Records of extreme precipitation were investigated using the Discrete Autoregressive Moving Average (DABMA) process, which can explain long persistences of wet and dry spells that exist in daily precipitation data. The results show that the daily precipitation with strong autocorrelation is inclined to be better fit by a Discrete Autoregressive (DAB) model. On the other hand, those data with weak autocorrelations tend to be best fit by a Discrete Moving Average (DMA) model. It can also be concluded that based on the records from extremely wet and dry regions there is no geographic preference regarding the selection of the best model.     

USABILITY ASSESSMENTS FOR HYDROLOGIC FORECASTING DSS1

ABSTRACT: Usability assessments were used to obtain feedback on the development of a flood forecasting decision support system. The feedback was used to guide design of system functionality, interface, training, implementation, and operations. The usability process was user focused and was dependent upon implementation of a prototype system in an operational setting. This paper describes concepts and methods applied to collect reflective and objective data on DSS components and information outputs. The general structure of the usability assessments is discussed and results of assessments are summarized.     

荆江分蓄洪区防洪基础信息演示系统的构建和运行

荆江分蓄洪区适时分蓄超过荆江河道安全泄量的洪水,确保荆江大堤、江汉平原和武汉三镇的安全,为长江防洪做出了贡献。为有效开展分洪管理防洪决策信息支持,构建了一套分蓄洪区的防洪基础地理信息演示系统。分析了以往构建系统中需求分析和信息组织的不足,较为详细地进行了需求分析,科学地进行数据组织及数据库设计,并在此基础上,采用原型法进行系统设计。最后利用控件Mapobjects,将GIS功能嵌入Visual Basic 6.0编制的应用程序中,实现用户需求的各种功能。系统整合了分蓄洪区基础地理数据、水利设施以及安全建设等数据,较好地反映了荆江分蓄洪区的现实特点和意义。系统的运行得到湖北省荆江分蓄洪区工程管理局的肯定。     

荆江分洪区土地利用时空动态变化研究

通过1986、1996 和 2002 年3期 Landsat TM＼ETM 遥感图像,分析得到荆江分洪区 1986～1996年 和 1996～2002 年土地利用变化情况及土地利用转移矩阵。17年来,荆江分洪区土地利用结构和强度发生了重大的变化。主要表现为：城乡居民及建设用地通过吞食大量耕地、林地而得到迅速增加,年均增幅达到9.66％;林地大规模减少,主要向农业用地和建设用地转变;由于研究区域水旱轮作,水田、旱地年际变化很大,主要根据市场行情决定作物种植。水域和滩涂也逐年减少,年均减幅分别为1.85％和3.34％。土地利用变化的主要驱动因素是人口的增长和经济的发展以及政策制度的激励和导向作用。根据荆江分洪区在整个长江防洪工程中的总体地位,根据分洪区应有别于非分洪区的政策和法规,采取国家扶持和引导,制定合理的规划和经济发展政策,调整区内土地利用结构和控制人口增长,实现分洪和经济可持续发展。     

江湖洪水不同遭遇对城陵矶水位影响的实验研究

城陵矶位于长江干流和洞庭湖出流汇合处,因此影响城陵矶洪水位的因素除了河床淤积、洪水特性等以外,洞庭湖出流与长江干流的不同遭遇也起着非常重要的作用。采用模型实验的方法,研究了不同遭遇、不同流量、不同螺山水位下城陵矶河段水位的变化。结果表明：在城陵矶断面,当监利来水流量超过洞庭湖出流时,主流靠左岸;当监利来水流量少于洞庭湖出流时,主流靠右岸。洞庭湖出流与长江干流来水流量的不同遭遇对城陵矶断面水位的影响非常显著。当监利来水流量占螺山流量的百分比为55 %左右时,城陵矶断面水位最高,即此时长江干流来水流量和洞庭湖出流相互之间顶托消耗能量达到最大值。在中水流量下,当监利来水流量占螺山流量的百分比为55 %左右时,城陵矶断面左右岸水位差达到最小值。     

洞庭湖区农业环境与湖垸农业可持续发展模式

围湖垦殖形成了洞庭湖区湖垸农业形式,湖垸农业的形成加速了湖区人口的增长,人口的压力也促进了围垦。不断的围湖垦殖使耕地面积迅速增加。由于湖泊面积减少,湖垸农业处于外洪内涝的环境中。归纳了洞庭湖区的农业环境问题：洪涝灾害发生频率加大;水面减少,生物多样性降低;环境污染严重,湿地生态功能衰退;土壤退化和潜育化严重;血吸虫病死灰复燃等。结合已有经验,提出了湖垸农业可持续发展模式：认真实施生态保护工程,减少泥沙淤积;调整湖垸农业结构,建立可持续发展生态农业模式：避灾、减灾模式、水生经济植物模式、工业原料作物模式、林农复合经营模式、湖洲草地草食畜禽模式、麻基（油菜）渔塘农业模式等。     

防洪预报调度方式下水库下游防洪风险分析--以葠窝水库为例

水库实施的防洪预报调度方式是解决我国防洪和兴利之间矛盾的一条有效途径,其对水库上下游的防洪风险率的大小是决定其能否实施的关键.目前对此缺少一种定量计算方法.本文在分析防洪预报调度方式风险指标的前提下,根据水库洪水径流深与产流预报误差的分布规律,采用数值分析方法计算水库实施防洪预报调度方式时,相对于常规调度方式,产流预报误差对水库下游防洪风险率,并以实例论述了具体分析思路和计算过程.     

Land use/cover change effects on floods with different return periods: a case study of Beijing, China

In this study, an approach integrating digital land use/cover change (LUCC) analysis, hydraulic modeling and statistical methods was applied to quantify the effect of LUCC on floods in terms of inundation extent, flood arrival time and maximum water depth. The study took Beijing as an example and analyzed five specific floods with return periods of 20-year, 50-year, 100-year, 1000-year and 10000-year on the basis of LUCC over a nine-year period from 1996 to 2004. The analysis reveals that 1) during the period of analysis Beijing experienced unprecedented LUCC; 2) LUCC can affect inundation extent and flood arrival time, and floods with longer return periods are more influenced; 3) LUCC can affect maximum water depth and floods with shorter return periods are more influenced; and 4) LUCC is a major flood security stressor for Beijing. It warns that those cities having experienced rapid expansion during recent decades in China are in danger of more serious floods and recommends that their actual land use patterns should be carefully assessed considering flood security. This integrated approach is demonstrated to be a useful tool for joint assessment, planning and management of land and water.     

东北三省农作物洪涝时空风险评估

仅考虑空间差异的灾害风险评估已经满足不了灾害风险管理向精细化方向发展的要求,增加时间维度的时空风险评估分析有利于增强风险评估结果,对提升风险管理的准确性与针对性起着重要的作用.以东北三省为研究区,在气象数据、地形数据、农作物灾情数据和种植面积数据的支撑下,以县和月为单位的时空两个维度开展农作物洪涝时空风险评估研究.在方法上,采用反距离权重法(IDW),利用与县行政区最临近的3个气象站点的日降雨数据插值出县级行政区的日降雨数据;利用二元回归建立农作物洪涝受灾率与过程降雨量、县平均高程之间的农作物洪涝脆弱性函数;分县分月提取过程降雨量,构建非参数核密度的信息扩散模型拟合降雨量的概率分布;综合概率分布与脆弱性函数,计算出分县分月的农作物洪涝条件期望受灾率,实现风险时空差异表达.最后,制作出东北三省县级尺度下4至9月的农作物洪涝风险差异图,并对风险时空差异规律进行分析.     

Trauma and short-fuse weather warning perceptions

The purpose of this research was to assess the importance of psychological trauma in understanding reactions to short lead time weather warnings. The research consisted of two case studies, one in Denver, Colorado and the other in Austin, Texas. A total of 61 individuals with 9 or greater traumas were compared to 281 non-trauma exposed individuals. Results demonstrated significant differences on questions related to general beliefs about flash floods and warning perceptions as well as reported anticipated actions during a flash flood at home. Results suggest high trauma exposure may lead to more threat sensitivity and a higher probability of initiated action in a home-based flash flood.