GIS-based flood risk assessment in suburban areas: a case study of the Fangshan District,Beijing

Suburban areas have become rapid development zones during China’s current urbanization. Generally, these areas are also regional precipitation centers that are prone to flood disasters. Therefore, it is important to assess the flood risk in suburban areas. In this study, flood risk was defined as the product of hazard and vulnerability based on disaster risk theory. A risk assessment index system was established, and the analytic hierarchy process method was used to determine the index weight. The Fangshan District in Beijing, China, which is an example of a typical suburban area undergoing rapid urbanization, was selected for this study. Six factors were considered in relation to hazard, and three factors were considered for vulnerability. Each indicator was discretized, standardized, weighted, and then combined to obtain the final flood risk map in a geographical information system environment. The results showed that the high and very high risk zones in the Fangshan District were primarily concentrated on Yingfeng Street, Xingcheng Street, Xincheng Street, and Chengguanzhen Street. The comparison to an actual flood disaster suggested that the method was effective and practical. The method can quantitatively reflect the relative magnitude and spatial distribution patterns of flood risk in a region. The method can be applied easily to most suburban areas in China for land use planning and flood risk management.     

UAV-borne,LiDAR-based elevation modelling: a method for improving local-scale urban flood risk assessment

Natural Hazards - In this study, we present the first findings of the potential utility of miniaturized light and detection ranging (LiDAR) scanners mounted on unmanned aerial vehicles (UAVs) for...     

Seismic risk assessment of buildings in urban areas: a case study for Denizli,Turkey

This study aims to carry out a seismic risk assessment for a typical mid-size city based on building inventory from a field study. Contributions were made to existing loss estimation methods for buildings. In particular, a procedure was introduced to estimate the seismic quality of buildings using a scoring scheme for the effective parameters in seismic behavior. Denizli, a typical mid-size city in Turkey, was used as a case study. The building inventory was conducted by trained observers in a selected region of Denizli that had the potential to be damaged from expected future earthquakes according to geological and geotechnical studies. Parameters that are known to have some effect on the seismic performance of the buildings during past earthquakes were collected during the inventory studies. The inventory includes data of about 3,466 buildings on 4,226 parcels. The evaluation of inventory data provided information about the distribution of building stock according to structural system, construction year, and vertical and plan irregularities. The inventory data and the proposed procedure were used to assess the building damage, and to determine casualty and shelter needs during the M6.3 and 7.0 scenario earthquakes, representing the most probable and maximum earthquakes in Denizli, respectively. The damage assessment and loss studies showed that significant casualties and economic losses can be expected in future earthquakes. Seismic risk assessment of reinforced concrete buildings also revealed the priorities among building groups. The vulnerability in decreasing order is: (1) buildings with 6 or more stories, (2) pre-1975 constructed buildings, and (3) buildings with 3–5 stories. The future studies for evaluating and reducing seismic risk for buildings should follow this priority order. All data of inventory, damage, and loss estimates were assembled in a Geographical Information System (GIS) database.     

Preliminary flood risk assessment: the case of Athens

Flood mapping, especially in urban areas, is a demanding task requiring substantial (and usually unavailable) data. However, with the recent introduction of the EU Floods Directive (2007/60/EC), the need for reliable, but cost effective, risk mapping at the regional scale is rising in the policy agenda. Methods are therefore required to allow for efficiently undertaking what the Directive terms “preliminary flood risk assessment,” in other words a screening of areas that could potentially be at risk of flooding and that consequently merit more detailed attention and analysis. Such methods cannot rely on modeling, as this would require more data and effort that is reasonable for this high-level, screening phase. This is especially true in urban areas, where modeling requires knowledge of the detailed urban terrain, the drainage networks, and their interactions. A GIS-based multicriteria flood risk assessment methodology was therefore developed and applied for the mapping of flood risk in urban areas. This approach quantifies the spatial distribution of flood risk and is able to deal with uncertainties in criteria values and to examine their influence on the overall flood risk assessment. It can further assess the spatially variable reliability of the resulting maps on the basis of the choice of method used to develop the maps. The approach is applied to the Greater Athens area and validated for its central and most urban part. A GIS database of economic, social, and environmental criteria contributing to flood risk was created. Three different multicriteria decision rules (Analytical Hierarchy Process, Weighted Linear Combination and Ordered Weighting Averaging) were applied, to produce the overall flood risk map of the area. To implement this methodology, the IDRISI Andes GIS software was customized and used. It is concluded that the results of the analysis are a reasonable representation of actual flood risk, on the basis of their comparison with historical flood events.     

A GIS-based tool for flood damage assessment and delineation of a methodology for future risk assessment: case study for Annotto Bay,Jamaica

Natural Hazards - Flood risk assessments and damage estimations form integral parts of the disaster risk management in Jamaica, owing its vulnerability to hydrometeorological hazards. Although...     

城市江堤外移工程对防洪影响研究

以浙江省温州市瓯江江堤外移工程为例,应用二维潮流数学模型研究了堤线外移的不同工程方案对城市防洪的影响。该模型能够模拟瓯江与楠溪江交汇引起的复杂水流运动,以及多岛屿对水流流场的影响。验证计算表明,计算的潮位及18条垂线流速及断面流量过程与实测值吻合较好,误差均小于10%。因堤线外移的部分大多位于河道岸线的凹囊,适当外移可使河道岸线更趋平顺。100年一遇洪水时,瓯江大桥至鱼旗山堤线外移曲线方案1与直线方案2分别使屿头山-梅岙河段最高潮位壅高0.03～0.04m及0.04～0.08m。多年平均流量450m3/s时,方案2使塔山至鱼旗山断面垂线平均流速增加6%～22%,工程段以外河段流速变化较小;方案1缩窄的河宽和拦截过水面积明显小于方案2,相应引起流速变化也较小。     

广州东濠涌流域城市洪涝灾害情景模拟与风险评估

绘制直观与可靠的城市洪涝灾害风险区划图,为城市防洪排涝相关部门决策提供参考依据。以广州市东濠涌流域为研究区域,综合考虑城市降雨、径流、地形和排水系统特性,构建基于InfoWorks ICM的一维-二维耦合城市洪涝仿真模型,模拟暴雨重现期为1年、5年、50年情景下的洪涝过程并获取致灾因子数据。调研分析区域的孕灾环境、承灾体和防灾减灾能力概况,结合层次分析法、评价等级和阈值划分等进行洪涝灾害风险评估。结果表明:城市洪涝仿真模型在一维排水系统和二维地面淹没模拟上均有较好的精度和可靠性,保证了致灾因子数据的可靠性;风险区划图能较好地反映流域的风险分布;随着重现期增大,较高、高风险区的面积显著增加,为防洪排涝重点关注区域。     

一种大比例尺的滑坡风险区划方法——以延安市区黄土滑坡风险评价为例

介于区域性和单体滑坡之间,即对面积几十到上百平方千米的滑坡评价,适用于1∶5000~1∶25000之间的大比例尺,而如何对这类区域进行有效的滑坡风险评价是一个值得研究的问题。使用传统的基于GIS的单元栅格运算方法对这类区域进行滑坡风险评价,由于反映评价指标的基础数据精度与评价方法之间的不匹配,无论单元网格划分得如何精细,评价结果仍难达到精度要求。采用一种新的思路和方法,先期通过高精度数字高程模型(DEM)和Quick Bird遥感数据等多信息源,识别潜在的滑坡易发坡体,并初步圈画滑坡的危险区界线和进行承灾体信息解译,再逐一通过野外核查对以上信息加以验证、修正或取消,最后形成符合比例尺精度要求的风险评价图。实践证明,这是一种行之有效的进行大比例尺风险区划和评价的方法。     

Integrating risk perceptions into flood risk management: Trinidad case study

Natural Hazards - Flooding disasters are frequent and devastating events in Trinidad. Moderate amounts of precipitation burst riverbanks in central business districts, cities, and towns within the...     

Integrated methodology for flood risk assessment and application in urban communities of Pakistan

Flood disasters and its consequent damages are on the rise globally. Pakistan has been experiencing an increase in flood frequency and severity along with resultant damages in the past. In addition to the regular practices of loss and damage estimation, current focus is on risk assessment of hazard-prone communities. Risk measurement is complex as scholars engaged in disaster science and management use different quantitative models with diverse interpretations. This study tries to provide clarity in conceptualizing disaster risk and proposes a risk assessment methodology with constituent components such as hazard, vulnerability (exposure and sensitivity) and coping/adaptive capacity. Three communities from different urban centers in Pakistan have been selected based on high flood frequency and intensity. A primary survey was conducted in selected urban communities to capture data on a number of variables relating to flood hazard, vulnerability and capacity to compute flood risk index. Households were categorized into different risk levels, such as can manage risk, can survive and cope, and cannot cope. It was found that risk levels varied significantly across the households of the three communities. Metropolitan city was found to be highly vulnerable as compared to smaller cities due to weak capacity. Households living in medium town had devised coping mechanisms to manage risk. The proposed methodology is tested and found operational for risk assessment of flood-prone areas and communities irrespective of locations and countries.     

A methodology for urban micro-scale coastal flood vulnerability and risk assessment and mapping

Natural Hazards - Wind gusts are a major cause of damage to property and the natural environment and a source of noise in seismic networks such as the USArray Transportable Array. Wind gusts cause...     

Hurricane flood risk assessment for the Yucatan and Campeche State coastal area

Natural Hazards - In this study, the first ever Sea, Lake, Overland Surges from Hurricanes (SLOSH) grid was built for the Yucatan Peninsula. The SLOSH model was used to simulate storm surges in the...     

城市岩溶塌陷地质灾害风险评估--以贵州六盘水市为例

岩溶塌陷是我国岩溶区主要地质灾害.它和崩塌、滑坡、泥石流以及地面沉降、地裂缝等构成我国6大地质灾害类型.随着我国"地质灾害防治管理办法”的颁布和实施,不同灾种的风险评估已成为地质灾害防治管理的重要内容.针对城市岩溶塌陷风险评估问题,中国地质科学院岩溶地质研究所塌陷项目组结合多年岩溶塌陷研究的经验,研制开发了基于GIS技术的岩溶塌陷灾害管理与风险评估系统(GMRS).本文以水城盆地为例,全面介绍运用GMRS进行岩溶塌陷风险评估的内容、方法和步骤,最后,对风险评估的结果作了详细讨论.     

Vulnerability assessment of an urban flood in Nigeria: Abeokuta flood 2007

The paper presents the result of a vulnerability assessment of urban dwellers to a major flood hazard in Abeokuta, southwestern Nigeria in July 2007. This was achieved by means of questionnaire survey administered to 248 flood area residents. Flood vulnerability was assessed by examining exposure, susceptibility, and coping indicators in the study area. Findings of the study show that although about 50% of respondents had experienced floods, in Abeokuta or elsewhere in the past, majority (66%) did not anticipate a flood event of such magnitude to occur despite its location on a flood plain and, therefore, were unprepared for such hazard. Pre-warning of the flood event was generally lacking among flood area residents as only 8% of respondents indicated pre-warning, which was based on personal observations. Response to the flood hazard was mainly reactive for both private and public agents as flood risk reduction measures were not in place.     

Public perception of flood hazard and flood risk in Iceland: a case study in a watershed prone to ice-jam floods

Understanding and improving the public perception has become an important element in the management of flood risk worldwide. In Iceland, studying perception of flood hazard and flood risk is, however, in its early stages. This paper presents a case study on the public perception of flood hazard and flood risk in an Icelandic town prone to ice-jam floods. Awareness of the population regarding historical inundations, self estimation of flood risk and worry is considered. The factual knowledge of the residents is deconstructed in flood hazard parameters accessible to the lay population: number of events, dates, genesis and boundaries. The performance of the respondents is rated for each parameter and the influence of several predictors evaluated. The research shows three significant patterns: there is poor awareness and little worry about historical inundations in the area; experience of the past flooding events in town is the most effective source of knowledge; awareness, risk estimation and worry are not correlated.     

Geological risk assessment by a fracture measurement procedure in an urban area of Zacatecas,Mexico

Natural Hazards - Geological hazards represent medium- and long-term risks, when they affect urban infrastructure and residential areas as they become a source of danger for the population. In...     

Application of analytical hierarchy process (AHP) for flood risk assessment: a case study in Malda district of West Bengal,India

A field experiment was conducted from 2 May 2010 to 1 May 2012 in the Gurbantunggut Desert, the second largest desert in China, to investigate saltation activity and its threshold velocity, and their relations with atmospheric and soil conditions. The results showed that saltation activity occurred more frequently during 08:00–20:00 Local Standard Time in spring and summer, with air temperatures between 20.0 and 29.0 °C, water vapor pressures between 0.6 and 0.9 kPa, soil temperatures between 25.0 and 30.0 °C, and a soil moisture lower than 0.04 m³/m³. At 2 m height, the saltation threshold velocity varied between 11.1 and 13.9 m/s, with a mean of 12.5 m/s. Threshold velocity showed clear seasonal variations in the following sequence: spring (11.7 m/s) < autumn (12.7 m/s) < summer (13.6 m/s). Affected by soil conditions, aeolian sand transport was weak, with an average annual aeolian sand that transported across a section (1.0 m × 2.0 m) of less than 6.0 kg.     

Heavy metal pollution and human health risk assessment for exposure to surface soil of mining area: a comprehensive study

Climate change projections indicate an increase in intense rainfall events with consequent river flooding, which could lead to devastating natural disaster     

Earthquake risk assessment in urban fabrics based on physical,socioeconomic and response capacity parameters (a case study: Tehran city)

Determination of the priorities for improvement of vulnerable urban fabrics based on a comprehensive assessment is among the main desires of local governments in earthquake-prone countries like Iran. However, in most countries, the comprehensive and absolute estimation of seismic risk is not possible due to shortages of the required data. In this paper, a new method is proposed for estimation of the risk through combination of hazard, vulnerability and response capacity indicators. Also, new evaluation methods based on relative scheme are presented for simple quantification of indicators in urban areas suffering from limited or insufficient database. For this purpose, important vulnerability parameters at urban areas are classified into physical, human life and socioeconomic groups. New hazard factors are also defined to evaluate the risk through combination of each vulnerability indicator and its directly related hazard factor. In addition, the capacity of response activities is accounted for in the model using planning, resource, accessibility and evacuation capacity indicators. The post-earthquake reduction of response capacity is also measured by means of reduction factors. Then, total relative seismic risk index is defined and calculated at each urban division (or zone) by weighted combination of the mentioned risk and response capacity indicators. This index represents the state of the risk in each zone in comparison with the others. The proposed method is applied to assess the earthquake risk at 22 municipal districts of Tehran. The results show that physical, human life and overall risk indices in district 15 of the city are considerably greater than the others. Meanwhile, in socioeconomic aspects, district 6 has the highest risk. Also, the analysis of the results demonstrates the major contribution of the response capacity term to determine the mitigation priorities. Finally, the results are compared with JICA (2000), using the same data, to show the efficiency of the proposed model. It is shown that the introduced method can significantly improve the results of the risk estimation and mitigation priorities.