气候变化背景下珠江流域极端洪水事件的变化趋势

根据1951-2010年珠江流域23个典型断面流量资料,用P-III型分布曲线拟合洪水系列进行频率计算,分析了珠江流域极端洪水事件的变化趋势。结果表明：1980年以来,珠江流域极端洪水事件发生的频次明显增加,尤其是自1990年以来增加趋势显著;1981-2010年较1951-1980年珠江流域约70%典型断面极端洪水事件呈增加趋势,主要分布在西江、北江、粤西;而近30%的典型断面呈减少趋势,主要分布在东江和桂南。     

张北-尚义地震震前阶段中小地震速度谱周期特征的研究

从 Duda 和 Nortmann 提出的谱震级定义出发,利用北京台网中小地震速度数字化记录资料,采用14组0.5倍频程滤波器组,其中心周期为:0.04s、0.06s、0.08s、0.12s、0.18s、0.28 s、0.40s、0.60s、0.96s、1.28s、2.40s、3.80s、6.20s、10.00s,分别计算了各中小地震的速度 谱综合因子f值,结果显示张北-尚义地震震前阶段中小地震的三分向速度谱卓越频率向高频 方向偏离,综合因子 f 值逐渐增加,且蓝地震的发生有向主震震中靠拢的趋势。同时,研究认为 综合因子 f 值可以量化蓝地震的定义。     

基于格网的洪水灾害危险性评价分析——以巴基斯坦为例

洪水灾害已成为给当今人类带来严重损失的自然灾害之一,因此,灾害风险评价是区域经济持续发展的前提与条件。本文从致灾因子和孕灾环境两方面进行分析,综合考虑降水(累计降雨量和最大降雨量)、河流(河网密度)、地形(高程值和坡度值)、土地利用和植被(NDVI)共5种相关因子,以1km格网数据为基础,运用AHP(层次分析法)对巴基斯坦洪水灾害进行了危险性评价。结果表明:巴基斯坦洪水灾害危险性受降雨和地形的影响较大,其危险程度东南部大于西北部,并由东南部向西北部逐渐递减。     

Flood hazard and risk analysis in the southwest region of Bangladesh

Flood hazard and risk assessment was conducted to identify the priority areas in the southwest region of Bangladesh for flood mitigation. Simulation of flood flow through the Gorai and Arial Khan river system and its floodplains was done by using a hydrodynamic model. After model calibration and verification, the model was used to simulate the flood flow of 100‐year return period for a duration of four months. The maximum flooding depths at different locations in the rivers and floodplains were determined. The process in determining long flooding durations at every grid point in the hydrodynamic model is laborious and time‐consuming. Therefore the flood durations were determined by using satellite images of the observed flood in 1988, which has a return period close to 100 years. Flood hazard assessment was done considering flooding depth and duration. By dividing the study area into smaller land units for hazard assessment, the hazard index and the hazard factor for each land unit for depth and duration of flooding were determined. From the hazard factors of the land units, a flood hazard map, which indicates the locations of different categories of hazard zones, was developed. It was found that 54% of the study area was in the medium hazard zone, 26% in the higher hazard zone and 20% in the lower hazard zone. Due to lack of sufficient flood damage data, flood damage vulnerability is simply considered proportional to population density. The flood risk factor of each land unit was determined as the product of the flood hazard factor and the vulnerability factor. Knowing the flood risk factors for the land units, a flood risk map was developed based on the risk factors. These maps are very useful for the inhabitants and floodplain management authorities to minimize flood damage and loss of human lives. Copyright © 2005 John Wiley & Sons, Ltd.     

DIAGNOSIS ON LOW FREQUENCY COMPONENT OF ENSO VARIABILITY—PART Ⅱ:ORIGIN OF THE COMPONENT

Diagnosis is undertaken on the origin for the low-frequency component (LFC) of ENSOvariability in the context of 1979—1990 OLR and u-wind datasets.Evidence suggests that ① apower spectrum-yielded maximum,significant statistically,is derived from the OLR monthlyanomalies in a 3—5-year period range over the tropical central/western Pacific;②compositeanalysis of the signals of the monthly anomaly low frequency component (period>3 years)confirms further the dynamic features of the component as documented in Part Ⅰ:③serving asforcing on ENSO,the related monsoon region represents the source area of the component;④theone-point correlation maps of unfiltered OLR monthly anomalies with zonal wind on a lagged,asimultaneous and a leading basis show clearly the close relation between the u wind-associatedeastward travelling low-frequency wave and the low-frequency oscillation of low-latitude central/western Pacific large-scale convection and the east-moving mode is likely to be excited by theoscillation at a 3—5-year period range.It follows that the large-scale convection oscillation showsup as the origin of the eastward waves,i.e.,ENSO LFC.     

同时满足多个阻尼反应谱的人造地震动时程合成

应用Ｍ．Ｈｉｒａｓａｗａ和Ｍ．Ｗａｔａｂｅ（１９９２）提出的方法,进行了相应的数学推导：即以满足某个阻尼比的反应谱的人造地震动作为初始时程,采用奇异值分解法,通过解线性方程组求出校正时程,并多次叠以逐步辐近     

洪水保险债券的运作机制与发展思路

由于传统(再)保险,难以将洪灾风险进行有效的分散,因此,有必要寻求有效的金融工具将洪灾风险向资本市场转移。在建立洪水保险债券的概念框架基础上,阐述了与普通债券及传统再保险的区别。从经济学和精算学的角度对洪水保险债券进行分析,揭示了洪水保险债券定价机制。通过研究洪水保险债券的运作模式,分析了我国洪水保险债券的发行条件与发展思路,指出洪水保险债券为我国防洪减灾提供了可资借鉴的崭新方法与工具。     

水库汛期限制水位控制理论与观念的更新探讨

传统的水库汛限水位的控制,只利用了洪水的统计信息,使水库在汛期要时刻预防设计与校核洪水事件的发生,致使一些水库在汛期不敢蓄水而汛后又无水可蓄,造成洪水资源的浪费。提出水库汛限水位动态控制的新理念及其综合推理模式,适应当前预报技术的发展水平,考虑降雨径流洪水预报与一定时间内的短期降雨预报,排除不可能发生的洪水事件,预报可能发生的洪水,实施水库汛限水位的动态控制。但预报不可避免地存在误差,当小概率预报误差事件发生时,仍可采取弥补措施以确保大坝的防洪安全。     

基于数值模拟的强震区典型泥石流堵江模式分析

受512汶川强震影响,大量崩滑体出现在震中岷江流域,伴随极端降雨天气它们逐步转化为泥石流灾害。2011年7月3日,受强降雨影响震中附近高家沟暴发泥石流,完全摧毁沟口地物,并且部分堵塞岷江,严重威胁高速公路隧道入口及国道。为了减少强震区泥石流堵江带来的损失,本文选取强震区岷江流域高家沟泥石流作为研究对象,采用数值模拟的方法,模拟不同降雨强度下（5a、20年、50a、100年）高家沟泥石流的运动特征,进而分析其不同程度的堵江模式。经过野外验证2011a73高家沟泥石流数值模拟精度可达81.4%,模拟结果表明,高家沟泥石流5年一遇降雨条件下没有松散堆积物冲出,20年一遇降雨条件下虽有部分松散堆积物进入岷江但未形成堵江,50年一遇降雨条件下则出现部分堵断岷江现象,100年一遇降雨条件下则完全堵塞岷江。该研究结果将为今后强震区泥石流堵江判识及监测预警提供科学依据。