An Area‐Based Approach for Estimating Extreme Precipitation Probability

Accurate estimates of heavy rainfall probabilities reduce loss of life, property, and infrastructure failure resulting from flooding. NOAA's Atlas‐14 provides point‐based precipitation exceedance probability estimates for a range of durations and recurrence intervals. While it has been used as an engineering reference, Atlas‐14 does not provide direct estimates of areal rainfall totals which provide a better predictor of flooding that leads to infrastructure failure, and more relevant input for storm water or hydrologic modeling. This study produces heavy precipitation exceedance probability estimates based on basin‐level precipitation totals. We adapted a Generalized Extreme Value distribution to estimate Intensity‐Duration‐Frequency curves from annual maximum totals. The method exploits a high‐resolution precipitation data set and uses a bootstrapping approach to borrow spatially across homogeneous regions, substituting space in lieu of long‐time series. We compared area‐based estimates of 1‐, 2‐, and 4‐day annual maximum total probabilities against point‐based estimates at rain gauges within watersheds impacted by five recent extraordinary precipitation and flooding events. We found considerable differences between point‐based and area‐based estimates. It suggests that caveats are needed when using pointed‐based estimates to represent areal estimates as model inputs for the purpose of storm water management and flood risk assessment.     

唐代长安、洛阳作为都城和陪都的气候原因

本文从气候角度探讨唐代以长安为都城、以洛阳为陪都的缘由。唐代由于气候温暖湿润,降水量增大,水灾增多。洛阳因为经度地带性作用、降雨季节分配不均及洛阳河流的特殊情况。使得水灾情况比长安更严重：一是降水量大、水灾次数多,二是水势大、灾情重。尽管唐政府注意治水修堤坝,但中桥被冲毁、雨水断路乃至宫城被淹之事仍屡屡发生。长安虽然旱灾较洛阳严重,但水灾对都城的危害更直接、更严重,灭顶之灾的威胁使洛阳不宜作都城,所以建都长安。     

Rainfall,floods and river channel changes in the upper Hunter

Since 1946, there has been a significant increase in annual rainfall in the Hunter Valley, especially for stations in the western sector. Contemporaneous increases in rainfall intensities of frequent storms and flood peaks have also been recorded. From analyses of the data, together with a review of recent environmental changes in the Hunter Valley, it is concluded that human disturbance of the catchment has played no significant part in the increase in flood magnitude. Instead, the change in floods may be completely attributed to the variation in rainfall regime. The altered hydrologic regime combined with a decrease in sediment yield from extra-channel sources appears to be the primary cause of recent river channel changes.     

Tropical mesoscale rainfall patterns: the opening of the monsoon in the Townsville area,December 1988

Rainfall during six days of monsoonal activity in the 1988/89 wet season is examined in terms of the influence of synoptic scale winds on mesoscale rainfall activity over the Townsville coastal plain (3450 km²). The resulting rainfall patterns. which were based on observations from a dense mesoscale network of 133 gauge points. are presented as isohyetal maps of twenty-four hour totals for each day in the study period. The study has shown that the distribution of rainfall is related to the influence of synoptic scale wind vectors, which provide upper level steering of convective activity. In addition. the interaction between local winds and synoptic circulation is deemed important for inducing convergence and precipitation. Rainfall generated is then directed by the prevailing upper synoptic flow. Orographic effects also appear to be significant, in that rainfall distribution tends to favour slopes on the windward side of the synoptic scale winds. The rainfall patterns described are probably typical of many of those that occurred throughout the 1988/89 wet season, due to the likely persistence of these mesoscale precipitation mechanisms. Similar mechanisms are also likely to occur over the study area in other wet seasons and elsewhere in the seasonally wet and dry tropics.     

明清时期山西的城市洪灾及其防治

明清时期山西的城市洪灾普遍而严重,曾遭受洪水冲击的城市达到62座。地方社会的防治措施大致可以归纳为“拦”、“疏”、“蓄”三类。具体而言,“拦”,即在城郊修筑拦洪堤堰以障水,这是明清山西城市防洪的主要措施,其中某些城市堤堰的筑造技术值得关注;“疏”,即通过开凿水口、疏浚城壕及新凿河渠等手段,使洪水远离城区;“蓄”,就是在城内利用既有低洼之地或新凿陂池,以蓄积雨洪。以上举措并未能彻底改变山西城市洪灾普遍且严重的状况,探究起来,城市的地理坐落、生态环境破坏导致的水土流失、城市建成区的扩展等,是不容忽视的三大诱发因素。     

Local government perceptions of water related issues in rural Australia

Water supply has long been regarded as a limiting resource in the further development of Australia. Active management has been necessary in both more densely settled areas and in areas of moderate settlement density but low rainfall such as the Murray-Darling system. The recently released Water 2000 Report details current knowledge about the quality and distribution of these resources. Following on from this Report this article presents perceived problems with water quantity and quality (in particular, salinisation) obtained from a survey sent to rural local governments in late 1982. The survey requested information on the relevance of twenty-two land use issues, known from earlier work to be representative of common concerns throughout Australia. Public perceptions were remarkably similar to the results of the Water 2000 Report. Water quantity/quality and salinisation issues were the sixth and seventh most commonly cited issues throughout Australia, but were of much greater concern in specific areas. Tasmanian local governments reported major problems of water supply, those in southwest Western Australia exhibited a very high level of concern with dry land salinisation, local governments in the Murray-Darling Drainage Division reported concern with salinisation, droughts, floods and general water quality, while local governments in the Gulf of Carpentaria Drainage Division consistently cited flooding as being a major problem. Information from surveys such as this, and others where the respondents are the end-users, need to be combined with expert opinion in order to increase the effectiveness of the management of our water resources.     

Ecohydrology and Environmental Change to Lake Albacutya and Wyperfeld Park in North‐Western Victoria,Australia

Lake Albacutya is a well‐known intermittent lake in north‐western Victoria. The lake is near the termination of the Wimmera River. From time‐to‐time the lake fills and flow passes down Outlet Creek into Wyperfeld National Park. The wetlands associated with the lake have a high biodiversity value and are named in international treaties. This paper examines the hydrologic factors associated with lake filling and flow into Wyperfeld. The lake has filled approximately six times since 1880 and has partially filled on other occasions. Examination of rainfall data from 1875 at Horsham gave no indication of long term rainfall decline, and showed that rainfall at Horsham can be viewed as representative of rainfall in the Wimmera River catchment. However a double‐mass analysis showed that the relationship between the Wimmera River flow and rainfall has varied from 1890 to the present. Examination of data associated with six fillings of Lake Albacutya suggested that filling is a two‐year event requiring at least 550 GL of flow passing Horsham over the two years immediately associated with the flood. A simple model based on rainfall and this threshold reproduced observed characteristics of the data reasonably well. This suggested that the flooding frequency of Lake Albacutya has dropped from about one in 25 years in the natural state to a substantially lower frequency under current river conditions. The results also suggested that because of changes in the Wimmera River the last filling and flood into Wyperfeld in 1976 was far smaller than it would otherwise have been. This is consistent with field mapping of the flood in relation to River Red Gum (Eucalyptus camaldulensis Dehnh.) stands. Analysis of the health of these stands showed major dieback with the severity of this being roughly proportional to the distance from the 1976 flood boundaries. An examination of values associated with the lake and adjoining Wyperfeld National Park suggested that biodiversity and economic values are and will be compromised by the reduction in flooding. In particular, an internationally‐known provenance of Red Gum is at risk, and bird‐breeding opportunities have diminished.     

Recent Hydrological Changes in the Avoca River Catchment,Victoria

Since the early 1970s the Avoca River catchment has experienced a marked increase in all discharges, particularly high magnitude ones. This results from a change in the rainfall/runoff relationship, which is probably due to rising groundwater tables. Since 1973 the frequency of flooding in the lower Avoca, Loddon and Avon-Richardson catchments has increased markedly, placing pressure on downstream flood mitigation and irrigation works, as well as contributing to the degradation of environmentally sensitive wetlands. It also has the potential to exacerbate rising groundwater/salinity problems of the lower catchments. Human interference and changes in the rainfall regime are assessed to explain the nature of the apparent change in streamflows of the Avoca River catchment.     

敦煌莫高窟降雨分布及入渗特征研究

敦煌莫高窟文物具有唯一性和脆弱性,干燥环境是壁画和塑像长久保存的保障,降雨是病害发生诱因。为了弄清降雨对文物的损害机制,本研究通过气象监测数据分析和野外人工降雨模拟试验,分析莫高窟降雨分布特征和窟顶戈壁降雨入渗和产流规律,为开展洞窟内壁画病害发育机理分析和实施莫高窟洪水风险预控提供理论依据。25年气象监测数据分析表明,莫高窟区域多年平均降水量39mm,集中在5~8月,降雨类型主要为微雨和小雨,频现大于76%,大雨及暴雨均为突发性强降雨,频现仅为1.5%,常常伴随区域洪水的发生。降雨模拟试验结果表明,当平均降雨强度0.75mm/min,降雨历时160min时,入渗湿润锋迁移至深度80cm左右即趋于平衡。但是,高密度电阻率探测表明洞窟地层2~3m处,水分饱和度可达60%左右,极易带动可溶盐向壁画地仗层富集,致使病害发生发展。经计算,窟顶戈壁径流系数0.016,产流能力非常低。区域洪水主要来源于莫高窟周边戈壁及野马山地带降雨汇流。     

莫高窟108窟内空气温湿度的变化过程及其对窟内水汽和热量来源的启示

为了对108窟内不同位置的温度、湿度和空气压力进行监测,设置了12个点的传感器。监测结果表明,窟内温度存在着显著的昼夜和长期的变化,其中上层空气的温度变化尤其明显,而下层空气的温度变化则相对较小。在夏天,窟内的上层空气温度高于下层空气的温度。窟内空气的绝对湿度受外部环境严重影响,存在近似昼夜的变化。在分布上,窟内空气湿度在上层和前部高,而在下层和后部则较小。窟内存在着净的水汽输入过程,但水汽不是从洞窟的入口进入的。同样,窟内的空气压力也存在着明显的昼夜变化过程,并受外部环境的影响而升高或下降,窟内东侧的空气压力大于西侧的空气压力。这些结果一致说明,在108窟的东侧上层存在着水汽和热量的来源。研究结果为下一步的盐害防治工作提供了思路,具有重要的科学意义和应用价值。     

Managing flood risk in the UK: towards an integration of social and technical perspectives

In recent years, an apparent increase in the frequency and severity of floods in the UK has led to growing concerns about societal exposure and vulnerability to flooding, particularly in the context of climate change, floodplain development and changing insurance practices. Despite the important link between assessments of exposure to flooding (hazard assessments) and issues of societal vulnerability, this link has rarely been explored in detail and has often been reflected in policy terms by a highly technocratic approach to flood risk management. Indeed, more comprehensive studies have usually favoured rigid and deterministic definitions of vulnerability, in keeping with the wider technocratic paradigm pervading management institutions. In an attempt to redress the balance, this paper considers the role of hazard assessment and issues of societal vulnerability as mutually informative debates and advocates a movement away from the technocratic ideals currently favoured in the UK.     

‘Torrents of Terror’: the August 1998 Storm and the Magnitude,Frequency and Impact of Major Floods in the Illawarra Region of New South Wales

The Illawarra Region some 80 kilometres south of Sydney is characterised by a prominent coastal escarpment that rises to 700 m within 12 km of the coast and forms a locus for frequent, high intensity rainfall events. One of the most recent recorded events occurred on 17 August 1998 with rainfall intensities at several pluviometers exceeding 120 mm hr^‐1 over a duration of one hour, with up to 249 mm falling in 3.5 hours during the main storm burst. Detailed pluviometer data indicate that the storm was non‐stationary and moved down catchment producing a widespread zone of 120 mm hr^‐1 intensity rainfall over a 30 minute duration across mid‐lower catchment areas after similar intensity but longer duration rainfall in catchment headwaters. Slope‐area reconstructions of peak discharge indicate that small catchments on the escarpment within the zone of maximum intensity experienced close to 100% rainfall‐runoff relationships, with peak discharges correlated to short duration (<1 hr) peak rainfall intensities. Widespread erosion occurred particularly where urban development had encroached on natural water courses. Debris/hyperconcentrated flows originating from both anthropogenic and natural sediment sources caused damage to urban areas. This paper provides an overview of the spatial and temporal characteristics of the 17 August 1998 storm, the hydrologic and geomorphic response of the streams, and the nature of damage to urban areas. It reassesses the frequency of recent high‐magnitude rainfall/flood events in the region, discussing the relationships between rainfall intensities, estimates of flood magnitudes and stormwater channel capacities.     

Shoreline Change and Coastal Vulnerability Characterization with Landsat Imagery: A Case Study in the Outer Hebrides,Scotland

Abstract

Observation of cause–effect patterns of change in coastal environments provides insights into vulnerable areas and supports prediction and adaptation to flooding and erosion. Historic and periodic (6–8 year intervals) imagery from the Landsat archive is used to investigate transformations in the Atlantic coast of two Scottish islands over the period 1989–2011. Supervised classification of spectrally normalized images followed by change detection and spatial analysis reveals the patterns of change and the location of the most dynamic coastal areas. Quantitative measures of recent shifts and movement rates of relevant coastal lines, such as the lower limit of land-based vegetation, are assessed with the Digital Shoreline Analysis System. While very low rates are indicated for horizontal changes in the position of the lower limit of land-based vegetation (0.3?m?y^?1), specific areas have been subjected to high rates of coastal progradation as well as erosion (e.g. 2.5?m?y^?1 at Stilligarry). Information derived from satellite data supports the characterization of geomorphologically dynamic coasts at regional scales. With a rich and open access archive of imagery, a commitment to continuity, and compatibility with the Earth observation missions of other space programs, the Landsat mission offers useful and otherwise unavailable data for monitoring of coastal areas.     

建国初期山区土改中的群众动员——以陕南土改为例

建国初期山区土改的顺利进行,离不开成功的群众动员。为了在旧势力强大、信息闭塞的山区把广大群众普遍地动员起来,土改工作组广泛开展了阶级教育、"谁养活谁"的教育和翻身教育。群众一经动员起来形成轰轰烈烈的群众运动,难免出现混乱现象,针对这种情况,中共中央、国务院、各省或下发文件予以指导纠正,或派人赴山区检查制止,使不正确的做法得到及时纠正,保证了土改工作在广泛发动群众的基础上没有发生太大的偏差,得以比较顺利地完成。     

降雨时长对土壤结皮发育性能的影响研究

室外土遗址经常因遭遇降雨、水淹等发生结皮,造成土遗址表层性能改变,影响土遗址的进一步保护。以定量纯净黄土在等降雨大小下,通过控制不同降雨时长,试验了不同降雨时长下土壤结皮发育的过程,分别测试了降雨前后的结皮厚度、密度、硬度及孔隙结构。结果表明,在降雨量未达到饱和状态时,随降雨量增大,结皮层的厚度、密度、硬度迅速增大,表皮土壤颗粒被击碎,孔隙迅速减小;在降雨量达到饱和状态时,随降雨量增大,结皮层的厚度、密度、硬度缓慢增大,但表皮土壤裂缝迅速发育,由周围向中心形成同心圆状或辐射状裂隙。研究结论可为室外土遗址的保护提供参考。     

Response to Wet Season Rainfall of an Alluvial Aquifer System in the Lower Herbert Floodplain,Queensland, Australia

Australia is one of the world's largest exporters of raw sugar. The lower Herbert River floodplain, one of the four main cane growing areas in Queensland, is subject to extremes of rainfall. Some areas are prone to waterlogging, which can lead to reductions in cane and sugar yields. This paper examines the risk of waterlogging and the role of surface drains in the Ripple Creek area, a subcatchment of the lower Herbert River floodplain. Following above‐average rains at the onset of this study, a perched water table developed and remained for the duration of the 19 month study. The responses of the perched watertable and a deeper semi‐confined aquifer following rainfall are examined. The rapid response of the perched water table following rainfall is attributed to the shallow depth of the water table, with soil properties exerting a dominant influence on hydrograph response. In the second year of the study, after above‐average rainfall, the water table of the deeper aquifer was on average 1 m higher than during the former months of the study. This trend, however, did not occur in the perched water table, and this is attributed to the efficiency of the surface drainage network.     

贵州民国档案中所见“疑似石漠化”与今日石漠化分布状况的比较研究

通过对贵州省民国时期档案与相关资料的分析,依据各县"不能生产之石山"占该县总面积的百分比,把相关39县划分为四个程度不同的"疑似石漠化"地区:重度石漠化地区(≥50%)、中度石漠化地区(<50%≥20%)、轻度石漠化地区(<20%≥5%)和无明显石漠化地区(<5%)。民国时期,毕节地区东部、安顺市、黔西南地区、铜仁及其周边地区的石漠化现象最为严重,除了铜仁及其周边地区,其他地区的石漠化状况与今日的吻合。民国时期石漠化严重程度与人口密度分布呈正相关,反映人类活动是石漠化扩张的主要原因。民国时期石漠化严重地区与碳酸盐岩的分布高度吻合,反映了石漠化的自然成因。     

Buffon's Needle and the Probability of Intercepting Short-Distance Trips by Multiple Screen-Line Surveys

For transport planning purposes, information on origin-destination movements may be obtained by stopping traffic at the roadside and interviewing drivers. The roadside interview stations are usually located so that they lie on one of a number of lines (called screen lines) that cross from one side of the survey area to another. In this way, all movements with the origin on one side of a screen line and the destination on the other are intercepted. For regional surveys, a grid of screen-lines may be used. The movements intercepted are not, however, representative of all those in the region. That is because shorter-distance movements are underrepresented; the coarser the grid, the worse the effect. The extent of this underrepresentation is estimated in this paper by calculating the probability of intercepting a trip of given direct length, under the assumption that the screen lines constitute a uniform rectangular grid, and that trips of a given length are distributed over the region at random. The result is an extension to the Buffon needle problem. Ways in which such a result, obtained for an idealized situation, may be extended to apply to more realistic situations, are discussed: in particular it is shown how the trip-length frequency distribution of all trips may be estimated from that of intercepted trips, using a simple formula that is applicable to a much more general pattern of screen lines.     

Mapping Mesolithic and Neolithic cultures behaviours and interactions with nature and properties of rocks in Western France

Multivariate statistical methods are used to study recent Prehistory lithics from the Armorican Massif, allowing us to classify them in more or less distinct groups according to the structural and mineralogical qualities of rock types involved. Analyses are carried out on metamorphic, sedimentary and magmatic rocks making up lithics collected from 31 localities. The petrographic properties are determined by polarizing microscope (POM), while the mechanical properties are obtained by Vickers's indentation method (VI), compression/traction (CT) and ultrasound echography (UE). The results provide us with important information about the management of lithic raw materials used by various human and cultural groups during the Mesolithic and Neolithic of the Armorican Massif. The more commonly used materials show a homogeneous and stable distribution of regional technology styles. The rock types exhibiting mature and homogeneous structures possess the better qualities for knapping (fracture energy G_Ic) and use (edge toughness M₁), and are more involved in exchange. The application of Upward Hierarchical Classification (UHC) and Principal Component Analysis (PCA) allows us to identify the classes of materials as well as the causes of variations of rock type abundance within the lithic assemblages of the Mesolithic and the Neolithic. In this way, we can then also predict the discovery of archaeological artefacts in areas lacking any known indications of the exploitation of outcropping materials.     

Absolute chronology of fluvial events in the Upper Dnieper River system and its palaeogeographic implications

A set of 121 radiocarbon and OSL dates has been compiled from the Upper Dnieper River and tributary valleys, Western European Russia. Each date was attributed according to geomorphic/sedimentological events and classes of fluvial activity. Summed probability density functions for each class were used to establish phases of increasing and reducing fluvial activity. The oldest detected reduction of fluvial activity was probably due to glacial damming at LGM. Within the Holocene three palaeohydrological epochs of millennial-scale were found: (1) high activity at 12,000–8,000 cal BP marked by large river palaeochannels; (2) low activity at 8,000–3,000 cal BP marked by formation of zonal-type soils on -floodplains; short episodes of high floods occurred between 6,500—4,400 cal BP; (3) contrasting hydrological oscillations since 3,000 cal BP with periods of high floods between 3,000–2,300 (2,000) and 900–100 cal BP separated by long interval of low floods 2,300 (2,000)-900 cal BP when floodplains were not inundated — zonal-type soils were developing and permanent settlements existed on floodplains. In the last millennium, four centennial-scale intervals were found: high flooding intervals are mid-11–mid-15^th century and mid-17–mid-20^th century. Intervals of flood activity similar to the present-day were: mid-15–mid-17^th century and since mid-19^th century till present. In the context of palaeohydrological changes, discussed are selected palaeogeographic issues such as: position of the glacial boundary at LGM, role of changing amounts of river runoff in the Black Sea level changes, floodplain occupation by Early Medieval population.