Mountain Effect and Differences in Storm Floods between Northern and Southern Sources of the Songhua River Basin

In this study, the differences in annual rainstorm changes in the Second Songhua River Basin and the Nenjiang River basin and their causes were compared from the perspective of mountain effects. The following results were drawn: (1) Altitude effect is the primary factor leading to increased rainstorms in the southern source; (2) Slope effect primarily leads to differences of the weather systems in the two sources, and thus cause the difference of the rainstorms; (3) Slope effect is responsible for the greater fluctuation in the observed floods in the southern source. These landform differences eventually lead to the differences in the characteristics of floods in the southern and northern sources. Commensurability method was used to identify the period of rainstorms in the southern and northern sources. The results showed that although rainstorms do not appear at the same time in the two sources they are characteristic of a 10 years' period in both areas. These results can serve as hydrological references for flood control and long-term flood disaster predictions.

Google Earth-based dynamic visualization system for storm surge flood routing

To describe the dynamic process of flood routing intuitively and realistically when storm surge disaster occurs,a method for ArcGIS data and Google Earth(GE) data integration is proposed,which realizes the importing and integrating of basic geographic information into GE. Based on SketchUp and AutoCAD software,threedimension(3D) visualization of seawall and other tidal defense structures is achieved. By employing Microsoft Foundation Class Library(MFC),the related system modules and storm surge flood routing dynamic visualization system are developed. Therefore,dynamic visualization of flood routing process and interactive query of submerged area and inundated depth are implemented. A practical application case study of Tianjin Binhai New Area provides decision-making support for coastal seawall planning and storm surge disaster prevention and reduction.

Assessment of Land Erosion and Sediment Accumulation Caused by Runoff after a Flash-Flooding Storm Using Topographic Profiles and Spectral Indices

This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectral indices (SI), and principal component analysis (PCA). To achieve our objectives, topographic attributes and profiles were retrieved from ASTER-V2 DEM. PCA and nine SI were derived from two Landsat-OLI images acquired before and after the flood-storm. The images data were atmospherically corrected, sensor radiometric drift calibrated, and geometric and topographic distortions rectified. For validation purposes, the acquired photos during the flood-storm, lithological and geological maps were used. The analysis of approximately 100 colour composite combinations in the RGB system permitted the selection of two combinations due to their potential for characterizing soil erosion classes and sediment accumulation. The first considers the “Intensity, NDWI and NMDI”, while the second associates form index (FI), brightness index (BI) and NDWI. These two combinations provide very good separating power between different levels of soil erosion and degradation. Moreover, the derived erosion risk and sediment accumulation map based on the selected spectral indices segmentation and topographic attributes and profiles illustrated the tendency of water accumulation in the landscape, and highlighted areas prone to both fast moving and pooling water. In addition, it demonstrated that the rainfall, the topographic morphology and the lithology are the major contributing factors for flash flooding, catastrophic inundation, and erosion risk in the study area. The runoff-water power delivers vulnerable topsoil and contributes strongly to the erosion process, and then transports soil material and sediment to the plain areas through waterpower and gravity. The originality of this research resides in its simplicity and rapidity to provide a solid basis strategy for regional policies to address the real causes of problems and risks in developing countries. Certainly, it can help in the improvement of the management of water regulation structures to develop a methodology to maximize the water storage capacity and to reduce the risks caused by floods in the Moroccan Atlas Mountain (Guelmim region).

产流模式空间分布对城市雨洪过程模拟的影响

通过耦合网格产流计算模型(GRGM)和暴雨洪水管理模型(SWMM)汇流计算模块构建了GRGM-SWMM模型。以贾鲁河中牟水文站控制流域(包括郑州市中心城区)为研究区,基于18场实测暴雨洪水资料探究了产流模式空间分布对洪水过程模拟精度的影响。结果表明:研究区超渗产流模式空间分布面积占比高达72%,城市下垫面仍以超渗产流模式为主;相较于仅考虑超渗产流计算的SWMM,考虑超渗、蓄满和混合等不同产流模式空间分布的GRGM-SWMM模型场次洪水产流量、流量过程模拟精度明显提高,产流量模拟相对误差平均降低33.26%、决定系数平均提高0.089,流量过程模拟均方根误差平均降低5.13 m^(3)/s、纳什效率系数和决定系数分别平均提高0.227、0.207。

沿海地面沉降对风暴潮作用下洪水淹没影响的析因试验

地面沉降会加剧沿海地区潮灾风险。基于验证良好的MIKE 21水动力模型预测珠海市未来地面沉降和风暴潮影响下洪水淹没情况,引入并设计析因试验以量化地面沉降和风暴潮对洪水淹没的单独效应、主效应和交互效应。结果表明:珠海市地面沉降在平沙镇东北至白蕉镇西南呈条带状分布,对洪水淹没存在空间“放大效应”。地面沉降和风暴潮交互作用会加剧鸡啼门水道和泥湾门水道两侧洪水向内陆演进的趋势;与内陆相比,沿岸农田和水产养殖区的淹没对地面沉降更为敏感。交互作用时两个因素的单独效应均增强,二者对洪水淹没存在正向协同交互作用。未来100年地面沉降情景下,地面沉降主效应约为风暴潮主效应的1.11~29.49倍,这表明地面沉降在淹没效应中占主导地位,在预测未来风暴淹没时须考虑地面沉降的影响。

基于MIKE FLOOD模型的湟水河上游洪水风险评估

湟水河上游段属于典型的山区性河段,河道比降大,暴雨洪水的突发性强,洪水流量大,历史短,具有巨大的破坏力,严重考验着河流的防洪能力。通过MIKE FLOOD耦合模型建立一二维水动力学模型评估现有防洪工程的防洪能力,预测了湟水河上游遭遇10年、50年、100年一遇洪水时的洪水风险情况,并且根据预测结果提出了相应的工程改进建议,为该地区的防洪救灾提供了技术支撑;同时根据计算结果也表明MIKE FLOOD耦合模型在山区性河流的风险评估中具有良好的适用性。

南京城市下垫面对夏季暴雨云团特征的影响

为了理解城市下垫面对降雨的影响机制,选取南京地区2次不同天气背景的降雨过程,利用中尺度气象模式和暴雨云团追踪算法开展数值试验,揭示城市下垫面对暴雨云团形态、结构和演进特征的影响机制。结果表明:当天气强迫较弱时,城市热岛效应增强大气边界层对流活动,暴雨云团进入城市后快速坍塌,云团数量减少,空间覆盖增大,降雨在城区增加;当天气强迫较强时,城市冠层影响暴雨云团特征,城市地区出现大量面积小、移动缓慢且空间结构“尖瘦”的暴雨云团,降雨在城区和城市下风向增加。城市下垫面对暴雨云团特征的影响与降雨前期天气强迫有关,更新了城市对降雨影响机制的传统认识,为城市地区暴雨临近预报和设计暴雨方法提供了科学支撑。

海平面上升情景下沿海城市极端雨潮复合洪涝危险性评估——以海口市为例

以海口市为例,利用1960—2017年的66场台风资料,包括台风日降雨和风暴潮的极值水位,建立复合洪涝组合情景。基于多个情景,对海口市在海平面上升背景下极端雨潮复合洪涝灾害的潜在风险进行深入研究。结果表明:1)在台风事件中,风暴潮为复合洪涝灾害的关键致灾因子,受灾最严重的地区主要位于南渡江入海口和北部滨海地区;2)在最大雨潮复合洪涝组合情景中,海口市受淹面积估计为148km^(2),相较于最小雨潮复合洪涝组合情景增加了约15倍,淹没区域中一半以上的区域积水深度超过1 m;3)在极端雨潮复合情景下,海甸岛、新埠岛及江东新区一带的滨海地区受到海平面上升影响最显著。根据RCP8.5情景预测,到2100年,海口市受极端复合洪涝灾害的影响区域预计达到约203km^(2)。

台风风暴潮与上游洪水耦合作用下温州飞云江感潮河段潮水位模拟研究

在全球气候急剧变化的背景下,沿海地区风暴潮发生的频率与受灾程度逐渐增加,特别是受风暴潮与上游流域洪水共同影响下的河口感潮河段区域。尽管现有风暴潮模型也引入多种不同的边界设置,但提供的边界条件有限,且无法满足当前国内复杂水工程的概化需求。为此,文章以飞云江流域为研究对象,通过耦合上游流域水动力模型IFMS与海洋风暴潮模型ADCIRC模式,充分发挥二者各自的优势,构建河口感潮河段洪水演进模型,实现飞云江感潮河段潮水位时空模拟。该模型不仅有效地考虑了河口海洋处风暴潮上溯对感潮河段区域洪水演进的影响,也考虑了流域上游洪水对该区域的影响。首先,采用2016年台风“鲇鱼”对模型进行验证,模拟结果与实测系列吻合度较高,误差满足基本要求。然后,对台风“杜苏芮”和“卡奴”影响下的瑞安、马屿、碧山六桥及洞头4个潮位站的洪水过程进行模拟,结果显示4个站点的洪峰误差值均低于0.30m,纳什系数大于0.80,表明该模型能较好地反映高低潮位变化,可应用于河口感潮河段防灾减灾中。最后,还分析了上、下游边界的驱动作用对感潮河段3个站点(瑞安、马屿、碧山六桥)潮水位预测的影响,证明了下边界对3个站点的潮水位预报影响比上边界的影响大。研究成果不仅为河口感潮河段洪水模拟提供了一种新方法,而且通过分析给出提升模型模拟精度的方向。

基于流溪河模型的任河流域城口段暴雨洪水模拟

为准确、有效地预报任河流域城口段暴雨洪水,以DEM、土地利用和土壤类型数据为基础,利用流溪河模型构建任河流域3级河道模型,选取20190627暴雨洪水手动优选模型参数,借助20170923、20180919暴雨洪水验证模型适用性;考虑降雨移动方向,利用优选模型模拟12 h降雨量为30、60、90、120、150 mm等5种情景洪水流量,分析各情景模拟特征。结果表明,参数优选后,20190627暴雨洪水洪峰误差减至2.79%,峰现时间提前5 h,模型模拟效果显著提升。20170923、20180919两次暴雨洪水洪峰误差小于20%、峰现误差小于3 h,满足模拟精度要求,流溪河模型可用于研究区暴雨洪水模拟。多情景下,30、60 mm降雨洪峰流量均小于150 m3/s;从90 mm降雨开始,洪峰流量急剧增加,增长率高达94.17%;降雨由上游往下游移动时洪水曲线至少出现1次峰值,反之洪水曲线仅有1次峰值,降雨量每增加30 mm,峰现时间提前1 h。流溪河模型在任河流域具有较好适用性,多情景模拟结果可为城口县设置暴雨洪水防治措施提供多视角支持。

有效不透水面分布对城市雨水径流的影响

城市区域不透水面分布错综复杂,汇流路径多样,不透水面有效性及其产流机制成为城市水文学的热点问题。研究以北京市主城区为对象,构建了基于汇水路径的有效不透水面的识别方法,拟合出总不透水面与有效不透水面的经验公式,定量识别了不透水面有效性对北京市主城区雨水径流的影响。结果表明:考虑不透水面有效性能显著提升模型模拟精度,针对不同城市化阶段,在各种重现期降雨情景下设置不同有效不透水面比例并进行模拟,发现有效不透水面对低重现期降雨产流过程的影响远大于高重现期降雨产流过程,且城市化前期有效不透水面增加会导致较大洪峰增长率,而城市化后期影响减小。研究可为优化城市地面格局,减缓城市洪涝灾害损失提供科学参考。

考虑Copula-LM-HMS耦联的台风情境下大坝洪水漫顶风险率计算

气候变化下台风风暴潮出现频次增加,形成的暴雨洪水对水库大坝安全产生极大威胁。由于部分地区实测流量资料缺少,基于雨量资料的随机模型与水文模型耦合模拟洪水过程线的研究亟待发展。针对现有小流域流量资料缺少问题,研究了基于降雨随机模型与水文模型的Copula-LM-HMS耦联模型,来模拟入库洪水并计算水库大坝洪水漫顶风险率。该模型通过Copula函数与拉丁超立方-蒙特卡罗抽样(Latin Hypercube-Monte Carlo Simulation)生成流域多组7日降雨数据,并通过变倍比放大法缩放处理得到相应降雨序列,利用HEC-HMS水文模型模拟洪水过程线并结合调洪演算得到坝前最高水位,同时考虑风浪作用来模拟台风情景下的库水位变化情况,计算大坝洪水漫顶风险率,并分析不同组合条件对洪水漫顶风险率的影响。余姚市四明湖水库实例分析表明,构建的Copula-LM-HMS耦合模型计算得到的拦河坝在未来台风情境下无漫顶风险,自溃坝最小漫顶风险为0.22%,最大漫顶风险达到2.68%;洪水漫顶风险与降雨分布及起调水位有关,同时风浪作用对洪水漫顶风险影响较大。基于耦合模型进行中小流域洪水漫顶风险率计算,不仅能考虑降雨系列之间的相关性、流域地形特征与实际调洪规则,还可延长无流量资料地区水库大坝应对台风情境下洪水风险的预报期,为保证水库大坝应对未来气候变化影响下的运行安全提供参考。

临泽县黑山口河“2022-08-13”暴雨洪水调查研究

文章对黑山口河“2022-08-13”暴雨洪水成因进行了分析研究,确定黑山口河此次洪峰流量为59.8 m3/s,重现期为百年一遇,调查研究了该暴雨洪水特性,为临泽县合黎山区针对强降雨、局部大洪水等突发性自然灾害的应急处置提供了数据支撑。

Influence of Land Use/Cover Change on Storm Runoff—A Case Study of Xitiaoxi River Basin in Upstream of Taihu Lake Watershed

Land use/cover change (LUCC) is one of the main boundary conditions which influence many hydrologic processes. In view of the importance of Taihu Lake Watershed in China and the urgency of discovering the impacts of LUCC on storm runoff, two flood events under five land cover scenarios in the Xitiaoxi River Basin of the upstream of Taihu Lake watershed were simulated by distributed hydrologic modeling system HEC-HMS. The influences of each land cover on storm runoff were discussed. It was concluded that under the same rainstorm the ascending order of runoff coefficient and peak flow produced by the 5 different land covers were woodland, shrub, grassland, arable land, and built-up land; the descending order of swelling time were woodland, shrub, grassland, arable land, and built-up land. Scenario of built-up land was the first to reach peak flow, then arable land, grassland, shrub, and woodland. There were close relationships between the runoff coefficients produced by the 5 different land covers. The degrees of impacts on runoff coefficient of land cover change modes were sorted by descending: woodland to built-up land, shrub to built-up land, grassland to built-up land, arable land to built-up land, woodland to arable land, shrub to arable land, arable land to grassland, shrub to grassland, grassland to arable land, and woodland to shrub. Urbanization will contribute to flood disaster, while forestation will mitigate flood disaster.

Rainfall occurrence and its relation to flood damage in China from 2000 to 2015

China is highly susceptible to flood disasters and subjected to great damage every year.Furthermore, the flood frequency has exhibited an increasing trend in recent years. Most flood events,including flash floods and river flood, are induced by rainfall. This study investigates annual variations of rainfall occurrence over China during the period from 2000 to 2015 at the national and regional scale using daily rainfall data from the Tropical Rainfall Measuring Mission. The Mann-Kendall test is performed for trend detection, and statistical data of flood damage published by China's government,including destroyed crop area, damaged buildings,direct economic loss, percentage of GDP(gross domestic product), and death toll are correlatively analysed with rainfall occurrences. The results show that storm rain events show the greatest variation among three rainfall types(moderate rain, heavy rain and storm rain). The variation coefficients of rainfall over Northeast China, North China, and Northwest China are the highest, whereas that for Southwest China is the smallest. Moderate rain, heavy rain over Central China, and moderate rain over Southwest China exhibits decreasing trends, whereas the remaining exhibit increasing trends. The correlation between the rainfall occurrences and these flood damage indices at the national scale shows that only direct economic loss has a strong positive correlation with rainfall occurrences, and the other indices have weaker correlations. The correlation is strong in three north regions, except for death toll in Northwest China. In contrast, the correlation between flood damage and rainfall is weak in East China, Central China, Southwest China, and South China. Overall,death toll is strongly correlated with the number of damaged buildings, implying that flood fatalities in China are likely associated with building collapse, and are dominated by specific extreme events. This study can provide a scientific reference for flood management in China.

Application of SWAN+ADCIRC to tide-surge and wave simulation in Gulf of Maine during Patriot's Day storm

The southern coast of the Gulf of Maine in the United States is prone to flooding caused by nor＇easters. A state-of-the-art fully-coupled model, the Simulating WAves Nearshore （SWAN） model with unstructured grids and the ADvanced CIRCulation （ADCIRC） model, was used to study the hydrodynamic response in the Gulf of Maine during the Patriot＇s Day storm of 2007, a notable example of nor＇easters in this area. The model predictions agree well with the observed tide-surges and waves during this storm event. Waves and circulation in the Gulf of Maine were analyzed. The Georges Bank plays an important role in dissipating wave energy through the bottom friction when waves propagate over the bank from offshore to the inner gulf due to its shallow bathymetry. Wave energy dissipation results in decreasing significant wave height （SWH） in the cross-bank direction and wave radiation stress gradient, which in turn induces changes in currents. While the tidal currents are dominant over the Georges Bank and in the Bay of Fundy, the residual currents generated by the meteorological forcing and waves are significant over the Georges Bank and in the coastal area and can reach 0.3 m/s and 0.2 m/s, respectively. In the vicinity of the coast, the longshore current generated by the surface wind stress and wave radiation stress acting parallel to the coastline is inversely proportional to the water depth and will eventually be limited by the bottom friction. The storm surge level reaches 0.8 m along the western periphery of the Gulf of Maine while the wave set-up due to radiation stress variation reaches 0.2 m. Therefore, it is significant to coastal flooding.

暴雨洪涝灾情快速监测评估技术框架体系与应用:以2022年6月北江流域洪水灾情分析为例

【目的】暴雨洪涝灾情快速评估在洪灾应急救援和灾后恢复重建中发挥着重要作用,但仍面临诸多挑战。为快速监测和评估洪涝灾情,建立一套集成天空地网多源信息与多种技术的暴雨洪涝灾情快速监测评估技术框架体系,【方法】以2022年6月北江暴雨洪灾为例,综合利用雨量、河道水位、网络淹没图片和视频、卫星遥感影像、地面调研测绘和无人机低空航测等多源数据、水文模型和地理空间分析技术,通过实地调研测绘和无人机航测,结合遥感影像、水力学模型和地理空间分析技术,快速识别本次洪水淹没深度范围、分析淹没区内的受灾人口、房屋、农田等基本灾情,在洪水灾情分析的实战中检验集成天空地网多源信息的暴雨洪涝灾情快速监测评估技术。【结果】结果显示:清远市新增的淹没面积为478 km^(2),其中淹没农田307 km^(2)(64%),淹没区内有74119栋房屋和167306人;韶关市新增的淹没面积为90 km^(2),其中淹没农田46 km^(2)(51%),淹没区内有15629栋房屋和78037人。【结论】结果表明:无人机航测结合地面RTK高程和洪痕测绘,将在洪涝灾情快速调查评估中发挥越来越重要的作用;卫星影像可快速揭示洪水淹没区的总体格局,但受云层遮档和过境时间的影响,难以获取最大淹没范围;洪涝淹没区公众提供的各类网络众包信息是最直接和现时的洪涝灾情信息,需要认真核实和充分利用;结合河道等各类实测水位,HAND模型可以快速估算出淹没深度范围,有很大的推广应用价值。通过对本次北江洪涝灾情的快速模拟和初步分析,充分展示了各类前沿技术在洪涝灾情快速识别中的独特作用,可为洪涝灾情应急监测方案设计和技术准备提供参考。

基于GIS构建邯郸市某区SWMM雨洪模型的方法研究

以河北省邯郸市某区雨水管网为例,通过建立GIS管网、划分子汇水区、构建地面高程图、绘制土地利用类型图及计算模型参数,借助GIS空间数据及融合理论和SWMM产流、汇流理论搭建雨洪模型,模拟4种不同重现期的降雨情境,验证模型的准确性,分析模型运行后雨水管网排水能力。结果表明,该方法建立模型的准确性高、适用性强,连续性误差均在5%以内,可直观反映雨洪情况。