AN ASSESSMENT OF FLOOD VULNERABILITY ZONES IN THE NIGER DELTA,NIGERIA

This study deals with an assessment of flood vulnerability zones in the Niger Delta region by using a hydrological technique based on some measurable physical characteristics of flooding and vulnerability factors. On the basis of these factors, 18 settlements randomly selected across the three ecological zones in the region were assessed. Three flood risk zones emerged from the analysis. These are severe flood risk zones, moderated flood risk zones and low flood risk zones. Strategies for mitigating the hazard of flooding in the region are recommended.     

高密度沿海地区洪涝风险评价与适应性规划策略 ——以深圳湾地区为例

气候变化背景下，高密度沿海城市受 到风暴潮和极端降雨引起的洪涝灾害冲击。文 章基于韧性理论构建城市空间洪涝风险指标 体系，制定该评价框架的实施路径；基于水文 软件Mike21、GIS平台及其空间网络分析插件 sDNA，复合“天鸽”台风风暴潮与极端降雨情 景，整合深圳湾地区的路网和土地利用进行危 险性、暴露度、脆弱性和适应能力等多源数据； 通过GIS栅格计算得到各要素层分析及洪涝风 险评价可视化地图，结果显示，潮、洪、涝突破 刚性标准加剧了危险性，高密度城市环境增大了 危险区域的暴露度，路网和土地利用布局具有 一定脆弱性，需完善应急疏散和避难场所规划以增强适应能力；根据评价地图识别高风险片区，从路网和土地利用等城市空间物质要素出发， 提出应对洪涝灾害的适应性规划策略。     

Flooding of municipal solid waste landfills — An environmental hazard?

Municipal solid waste (MSW) landfills pose a long-lasting risk for humans and the environment. While landfill emissions under regular operating conditions are well investigated, landfill behaviour and associated emissions in case of flooding are widely unknown, although damages have been documented. This paper aims at developing a methodology for determining the proportion of MSW landfills endangered by flooding, and at evaluating the impact flooded landfills might have on the environment during a flood event.The risk of flooding of MSW landfills is assessed by using information about flood risk zones. Out of 1064 landfills investigated in Austria, 312 sites or about 30% are located in or next to areas flooded on average once in 200 years. Around 5% of these landfills are equipped with flood protection facilities. Material inventories of 147 landfill sites endangered by flooding are established, and potential emissions during a flood event are estimated by assuming the worst case of complete landfill leaching and erosion. The environmental relevance of emissions during flooding is discussed on the basis of a case study in the western part of Austria. Although environmental hazards need to be assessed on a site- and event-specific basis, the results indicate that flooded MSW landfills represent in general small environmental risks for the period of flooding. The longer term consequences of flooding are discussed in a next paper.     

海峡科技生态城·竖向标高规划设计探讨

紧密结合海峡科技生态城防洪排涝规划设计,通过园区竖向标高规划设计实践,提出滨海园区竖向规划的一般步骤及技术路线,运用防洪排涝规划分析论证了园区的竖向规划与洪水、涝水、海潮的关系,论述了园区竖向规划确定的思路和办法,如:海堤御潮,高水高排,涝水蓄排兼顾等。     

厦门海沧新城内湖湖水调蓄分析

本文从海沧新城防洪规划,新城城市设计,内湖景观规划出发,通过对内湖排水计算,提出湖水调蓄方法,并强调内湖涵闸管理对内湖景观功能与防洪功能实现的重要性。     

Stratification and fine sediment transport mechanisms in a semi-enclosed tidal lagoon (Pagham Harbour, West Sussex)

Preliminary analysis of data collected at a macrotidal semi‐enclosed lagoon (Pagham Harbour, UK) has revealed useful information about long‐term patterns of siltation and some of the related mechanisms. Sediment surface‐level measurements made over 2 years at different sites within Pagham Harbour have shown a steady siltation, in common with earlier measurements, which is moderated by seasonal effects due to erosion by locally generated waves. Furthermore, inspection of vertical profiles of salinity and turbidity over individual tidal cycles has revealed that the degree of sediment transport on the flood tide is related to the vertical salinity gradient. Thus, at the Ferry Pool site, which is characterised by episodic pumped discharges from a nearby sewage treatment plant, landward sediment transport is enhanced by the high degree of salinity stratification observed during the flood tide. The mobility of the sediment, and the greater distribution of softer, less well‐consolidated sediment deposits, is greater here than at the other significant freshwater inflow at the Salthouse site, where the fresh water flow is instead moderated by a tidal flap gate. Preliminary analyses suggest that the higher the salinity stratification, the greater the landward sediment transport during the flood tide. Such analyses could help inform future policy on the methods of land drainage to macrotidal lagoons, and on the potential for managed realignment at such sites.     

Re-assessing the flood risk in Scotland

This paper presents a review of changes in flood risk estimation on Scottish rivers resulting from re-analysis of flood records or from the application of new methods. The review arises at a time when flood damages have received recent prominence through the occurrence of a number of extreme floods in Scotland, and when the possible impacts of climate change on flood risk are receiving considerable attention. An analysis of the nine longest available peaks-over-threshold (POT) flood series for Scottish rivers reveals that, for thresholds yielding two events per year on average, annual POT frequencies on western rivers have increased in the 1980s/1990s to maximum recorded values, while in the east, values were highest in the 1950s/1960s. These results support the results of flood modelling work based on rainfall and temperature records from the 1870s, which indicate that, in western catchments, annual POT frequencies in the 1980s/1990s are unprecedented. No general trends in flood magnitude series were found, but an unexpected cluster of extreme floods is identified as having occurred since 1988, resulting in eight of Scotland's 16 largest gauged rivers producing their maximum recorded flows since then. These shifts are related to recent increases in the dominance of westerly airflows, share similarities with the results of climate change modelling, and collectively point to increases in flood risk in many parts of Scotland. The paper also reviews advances in flood risk estimation arising from the publication of the UK Flood Estimation Handbook, developments in the collection and use of historic flood estimation and the production of maps of 100-year flood areal extent. Finally the challenges in flood risk estimation posed by climate change are examined, particularly in relation to the assumption of stationarity.     

中国矿震受区域应力场影响的探讨

对中国矿震受区域应力场影响问题,探讨了矿震与固体潮之间的相关性,发现矿震发生与月球固体潮有较好的相关性;探讨了矿震与其附近区域天然地震在时间上的相关性,发现天然地震较矿震具有滞后性;探讨了矿震空间分布规律,发现在平面分布上发生矿震的矿井也属于天然地震的多发地带,而且几乎都分布在构造活动性强的地震带内;在深度分布上,存在着发生矿震的临界深度。矿震的发生受区域应力场的影响,区域应力场是影响矿震发生的重要因素。     

Implementation of the floods directive in selected EU member states

To reduce the flood risk at European scale, the Floods Directive (FD) became into force in 2007. Each member state had transposed the directive in national laws and guidelines, generating a quite spotted situation. This work is intended to compare and briefly assess the implementation process on rivers in selected European countries by means of the available literature and a specific questionnaire. Different structures, methodologies and data conditions used for preliminary flood risk assessment, flood hazard maps, flood risk maps and flood risk management plans are here presented and analysed. To minimise the flood risk, the technical differences between the EU countries need to be reduced in the next implementation cycles of the FD.     

Modeling water flow and bacterial transport in undisturbed lysimeters under irrigations of dairy shed effluent and water using HYDRUS-1D

HYDRUS-1D was used to simulate water flow and leaching of fecal coliforms and bromide (Br) through six undisturbed soil lysimeters (70 cm depth by 50 cm diameter) under field conditions. Dairy shed effluent (DSE) spiked with Br was applied to the lysimeters, which contained fine sandy loam layers. This application was followed by fortnightly spray or flood water irrigation. Soil water contents were measured at four soil depths over 171 days, and leachate was collected from the bottom. The post-DSE period simulations yielded a generally decreased saturated water content compared to the pre-DSE period, and an increased saturated hydraulic conductivity and air-entry index, suggesting that changes in soil hydraulic properties (e.g. via changes in structure) can be induced by irrigation and seasonal effects. The single-porosity flow model was successful in simulating water flow under natural climatic conditions and spray irrigation. However, for lysimeters under flood irrigation, when the effect of preferential flow paths becomes more significant, the good agreement between predicted and observed water contents could only be achieved by using a dual-porosity flow model. Results derived from a mobile-immobile transport model suggest that compared to Br, bacteria were transported through a narrower pore-network with less mass exchange between mobile and immobile water zones. Our study suggests that soils with higher topsoil clay content and soils under flood irrigation are at a high risk of bacteria leaching through preferential flow paths. Irrigation management strategies must minimize the effect of preferential flow to reduce bacterial leaching from land applications of effluent.     

增强现实技术于洪水风险沟通中的应用

气候变迁,特别是洪水问题给地处三角洲的城市带来了与日俱增的风险。作为应对手段,提出一种整合性的洪水风险管理方法,该方法确保了洪水风险沟通在洪水风险管理战略中的重要地位。洪水的可视化作为洪水风险沟通的一种工具,在改变人们对洪水风险的观念方面有着强大的作用。它可以通过互动的方式,使当地的利益相关者了解洪水的剩余风险和未来风险。其中增强现实技术作为一种可视化手段,它的快速发展与应用为风景园林设计、规划与教育等领域提供了崭新的交互方式。首先,探讨增强现实技术(AR)在洪水风险沟通中的应用现状,并重点关注增强现实技术的2个关键应用领域:对现场决策的支持和针对高层次设计的可视化与对景观干预的评估。随后,展示一种基于增强现实技术所开发的应用,该款创新性的应用为洪水风险沟通提供了一种轻量化的可视化手段。     

Flow measurement with multi‐instrumentation in a tidal‐affected river

Flow measurements in a tidal‐affected river provide important information of cyclic flow pattern characteristics in temporal and spatial variations. Reliability and accuracy of measured flow data can provide for numerical model calibration and verification. In the present study, we measured tidally affected river flow in the Danshui River of northern Taiwan during the 2008 summer and fall. The measured flow data, produced by both state of the art and conventional instruments including particle tracking velocimetry (PTV), acoustic Doppler profiler (ADP), horizontal acoustic Doppler current profiler (H‐ADCP) and Price‐type current metre (PCM) were compared and correlated during several tidal cycles. The mean flows by ADP were similar to that by PCM and highly correlated with those by PTV and H‐ADCP. Index velocity rating between ADP and H‐ADCP separately computed during the flood and ebb tides shows good correlation for the ebb tide and poor correlation for the flood tide due to subsurface maximum velocity in the middle‐ to near‐bottom layers.     

The impact of flood risk on the price of residential properties: the case of England

This paper examines the impact of flood risk on the value of English residential properties. We find that a location within a flood zone significantly lowers property values even if we control for the proximity to a watercourse, the history of flooding and neighbourhoods effects. Although the flood risk discount is more compelling for waterfront properties, it is still highly significant for dwellings further from the water. The markdown arises around 2004–2005, which coincides with the publication of detailed flood maps by the UK Environment Agency and with a more risk-based pricing of flood insurance policies. As expected, the effect of flood risk on house prices is stronger in the months following major flood events but, interestingly, it almost disappears in a hot market when buyers have arguably less negotiating power.     

Hochwasserschutzdeiche – aktuelle Entwicklungen zur Verbesserung der Hochwassersicherheit

River dikes – actual developments for improvement in flood safety. For centuries dikes have been constructed along rivers as protection against flooding at high water levels and they still exist today over long stretches. In the course of time numerous changes have occurred concerning the materials to be used and the inner structure when building dikes, so that a dike constructed in several zones according to today's technical standards generally holds out under prolonged hydraulic stress. Many related questions arise with regard to the subject of flood safety. In this article specific examples of current developments are taken and illustrated with reference to the assessment, prognosis and improvement of the stability of flood protection dikes, in particular of old dikes.     

Uncertainty in risk of highway bridges assessed for integrated seismic and flood hazards

Probabilistic risk assessment for bridges under natural hazards is of great interest to engineers for the development of risk mitigation strategies and implementation plans. The present study evaluates risk of an existing highway bridge in California, USA, under the integrated impact of regional seismic and flood hazards. A sensitivity study combining tornado diagram and first-order second moment reliability analyses is conducted to screen significant uncertain parameters to which bridge response is mostly sensitive. A rigorous uncertainty analysis, employing random sampling and Monte Carlo simulation techniques, is performed to obtain variations in fragility and risk curves of the bridge. Observed variations in risk curves at various risk levels are quantified through 90% confidence intervals and coefficients of variation (COV) of risk. It is observed that uncertainty in the estimated risk increases due to the presence of flood hazard at the bridge site, although mean risk does not vary with flood hazard level. Research outcome signifies that the variation in risk due to parameter uncertainty and varied flood hazard level should not be ignored to ensure bridge safety under the stated multi-hazard condition.     

The sensitivity of fluvial flood risk in Irish catchments to the range of IPCC AR4 climate change scenarios

In the face of increased flood risk responsible authorities have set out safety margins to incorporate climate change impacts in building robust flood infrastructure. Using the case study of four catchments in Ireland, this study subjects such design allowances to a sensitivity analysis of the uncertainty inherent in estimates of future flood risk. Uncertainty in flood quantiles is quantified using regionalised climate scenarios derived from a large number of GCMs (17), forced with three SRES emissions scenarios. In terms of hydrological response uncertainty within and between hydrological models is assessed using the GLUE framework. Regionalisation is achieved using a change factor method to infer changes in the parameters of a weather generator using monthly output from the GCMs, while flood frequency analysis is conducted using the method of probability weighted moments to fit the Generalised Extreme Value distribution to ~ 20,000 annual maximia series. Sensitivity results show that for low frequency events, the risk of exceedence of design allowances is greater than for more frequent events, with considerable implications for critical infrastructure. Peak flows for the five return periods assessed were found to be less sensitive to temperature and subsequently to potential evaporation (PET) than to rainfall. The average width of the uncertainty range for changes in flood magnitude is greater for low frequency events than for high frequency events. In all catchments there is a progressive increase in the peak flows associated with the 5, 25, 50 and 100-year return periods when moving from the 2020s to the 2080s.     

COMPENSATING FLOOD RETENTION ON PRIVATE LAND IN AUSTRIA: TOWARDS POLYCENTRIC GOVERNANCE IN FLOOD RISK MANAGEMENT?

Flood retention, in particular controlled flood retention, plays an increasingly prominent role in the portfolio of flood risk management strategies. Though a highly effective measure to reduce the risk of flooding for vulnerable areas, flood retention is land-intensive and infringes on landowners’ property rights. Implementation efforts are thus often hampered by the lack of availability of land as well as by the growing demands of (agricultural) landowners for compensation of flood retention services. The proliferation of flood retention not only changes riparian land uses but also results in a shift of authority, power, and agency to lower levels of government as well as to non-governmental actors, including the private landowners who provide the land for flooding but also those who benefit from flood retention. By the example of a compensation scheme for the controlled flood retention in Altenmarkt, an alpine municipality in Austria, this paper explores these nascent forms of governance through the lens of polycentricity. Along five core propositions in polycentric theory, the paper evaluates the governance implications of flood retention compensation in Austria and discusses the possibilities and limitations of flood retention for enhancing landscape resilience in riparian areas.     

波浪作用下钢管桩连接平台前后动力响应的试验研究

对波浪作用下东海大桥附近海上风电场钢管桩基础在连接平台前后的动态反应进行了原位测试。通过放置在桩顶的加速度传感器测得桩顶的加速度时程曲线,将加速度时程曲线进行2次积分得到桩顶的位移时程曲线。对比实测结果,涨潮期间所测得的桩顶位移大于平潮期;钢管桩与平台连接后,在波浪作用下的位移小于连接前。运用Morison方程计算出桩身的所受的波浪力,并采用m法对桩身的变形进行计算,对比现场实测值,计算所得结果小于测试结果。     

Schutz flussnaher Trinkwasserfassungen bei Flussraum-Aufweitungen in voralpinen Schotterebenen

In alpine and peri-alpine flood plains, rivers can lose water to the ground water (infiltrating conditions), or gain water from it (exfiltrating conditions). Since sediments within these flood plains are highly permeable, drinking water wells near infiltrating rivers are often highly efficient. To reduce flood risks, engineers couple hydraulic flood protection measures with an enhancement of lateral connectivity. Eventually, the residence time of the infiltrating ground water is reduced and the fraction of infiltrated water rises. Floods lead to the breakthrough of freshly infiltrated water. This can lead to groundwater contamination, if the river is loaded with wastewater. Where measures of hydraulic engineering are necessary, drinking-water wells must therefore be protected from contamination. We discuss three cases of contamination risk: i) low risk under exfiltrating conditions or where river and ground water interaction is weak, ii) increased risk during or after hydraulic operations under infiltration conditions; and iii) generally high risk at wells with low residence times and high fractions of infiltration water. We suggest that the risk is reduced when a thick unsaturated zone separates the river from the well (> 10?m), compared to direct water loss through saturated media. For wells at risk, we propose technical protection measures to reduce the danger.     

Climate-related uncertainties in urban exposure to sea level rise and storm surge flooding: a multi-temporal and multi-scenario analysis

Climate change-induced sea level rise and intensified storms pose emerging flood threats to global coastal urban areas. While such threats have been mapped, their uncertainties from different climate scenarios and longer planning horizons have yet to be addressed from both an exposure assessment and a stakeholder outreach perspective. Therefore, we chose the highly urbanized San Francisco Bay Area as an example to project its flood areas every 20 years between 2000 and 2100, under 24 varied climate scenarios with two greenhouse gas (GHG) concentration levels. We then assessed flood exposure by intersecting the flood areas with demographic and socioeconomic distributions, developed areas, lifeline infrastructures, and emergency responders in low elevation (<10 m) coastal zones. Our median estimates under the low GHG scenarios indicated that 10–38% of the items assessed above are flood-exposed in 2000–2020, with this exposure increasing to 20–54% during 2080–2100. The median estimates under the high GHG scenarios for the same periods are 0–35% and 40–67%, respectively. The expected uncertainties, or standard deviations, of the exposures for a given item assessed above under the low and high GHG scenarios are 1–2% in 2000–2020 and 7–10% in 2080–2100. Despite our modeling capability for a range of climate scenarios over the long term, some stakeholders, particularly those in the private sector, prefer near-term results with lower uncertainties. This implies the need for coastal urban areas to cope with climate-related uncertainties and to focus on the long term when developing strategies and policies for climate change adaptation.