Analysis of Forecast and Early Warning of Flood in Medium and Small Rivers

Flooding of small and medium rivers is caused by environmental factors like rainfall and soil loosening.With the development and application of technologies such as the Internet of Things and big data,the disaster supervision and management of large river basins in China has improved over the years.However,due to the frequent floods in small and medium-sized rivers in our country,the current prediction and early warning of small and medium-sized rivers is not accurate enough;it is difficult to realize real-time monitoring of small and medium-sized rivers,and it is also impossible to obtain corresponding data and information in time.Therefore,the construction and application of small and medium-sized river prediction and early warning systems should be further improved.This paper presents an analysis and discussion on flood forecasting and early warning systems for small and medium-sized rivers in detail,and corresponding strategies to improve the effect of forecasting and early warning systems are proposed.

Responses of Nutrients to the Precipitation Variation and Land Use in Subtropical Monsoonal Small Mountainous Rivers:A Case Study of Baixi Watershed

Small mountainous rivers are characterized by large instantaneous fluxes and susceptible to extreme weather events,which can rapidly transport materials into the sea and have a significant impact on the ecological environment of estuaries and bays.In order to investigate the seasonal characteristics of nutrients in small mountainous rivers in the subtropical monsoon region and the output pattern to the sea during heavy precipitation,surveys on the mountainous rivers were carried out in Baixi watershed in August 2020(wet season),March 2021(dry season)and June 2021(Meiyu period).The results showed that the dissolved inorganic nitrogen(DIN)of the rivers has an average concentration of 752μg L^(−1)in the wet season and 1472μg L^(−1)in the dry season.The concentrations of dissolved inorganic phosphorus(DIP)in wet season and dry season were 63μg L^(−1)and 51μg L^(−1),respectively.Influenced by the changes of land use in sub-watersheds,DIN concentrations in the mainstream increased from 701μg L^(−1)in the upper reaches to 1284μg L^(−1)in the middle reaches.Two rainstorms during the Meiyu period in the watershed caused the pulse runoff in the river.The maximum daily runoff reached 70 times that before rains.The maximum daily fluxes of DIN and DIP were 109 and 247 times that before rains,respectively.In view that the watershed experienced several rainstorms in the wet season,the river,with pulse runoff,carries a large amount of nutrients into the sea in a short time,which will have a significant impact on the environment of Sanmen bay and its adjacent sea.

Influence of the interaction of calcium carbonate particles with surfactants on the degree of water pollution in small rivers

Introduction:The influence of the interaction of calcium carbonate(CaCO3)and surface-active substances(SAS;surfactants)with different chain lengths and cationic and anionic hydrophilic centers has been analyzed.Results:Laboratory simulations indicate reduced negative influences on cationic SAS nitrification/self-purification processes in the presence of anionic species.This suggests the role of complex ionic formation[anionic SAS*cationic SAS]as a cause of this effect.UV-Vis spectra of lauryl sulfate(LS)and of cetyltrimethylammonium(CTMA),as well as of their mixtures in ratios of 2:1 and 1:1,treated by fine particles of CaCO3,display decreased amounts of SAS in analyzed solutions and their presence on the surface of CaCO3 nanoparticles.UV-Vis spectra reveal the decomposition of the complex[anionic SAS(SAS-An)*cationic SAS(SAS-Ct)]in solutions when CaCO3 is added.CTMA can be bonded by LS through hydrophobic chains,on the surface of CaCO3 particles.Therefore,CaCO3 modifies the nature of LS and CTMA interactions.This leads to an increased degree of toxicity of cationic SAS in aquatic environment.The amounts of CTMA in aqueous solutions are diminished in the presence of ammonium ion NH4+(2 mg/L).In the presence of two orders higher concentration of ammonium ion,this effect strongly increases,making the association obvious.The structure of cationic SAS does not influence this effect.The obtained results have been confirmed both by timed natural aquatic sample analysis and laboratory simulations using water from Moldovan small rivers(Isnovat,Raut,and Bic).Conclusions:UV-Vis spectra and laboratory simulations demonstrate the change due to the addition of calcium carbonate.Simulations and laboratory tests of water samples from Isnovat,Bic,and Raut Rivers,establish the cationic SAS negative influence on treatment and self-purification processes.

Ecological Environment Problems and Countermeasures of Small and Middle-sized Rivers in Shandong Province

Water uses in small and middle-sized rivers, and non-ecological treatment model has deteriorated local environment in Shandong. The research reviewed ecological environment status quo of small and middle rivers and concluded existing problems. Finally, ecological treatments were proposed based on treatments at home and abroad in order to improve eco-environment of rivers and build better Shandong.

The effect of wind on the dispersal of a tropical small river plume

Wanquan River is a small river located in Hainan, a tropical island in China. As the third largest river in Hainan, the river plume plays an important role in the regional terrigenous mass transport, coastal circulation, and the coral reef＇s ecosystem. Studies have shown that wind forcings significantly influence river plume dynamics. In this study, wind effects on the dispersal of the river plume and freshwater transport were examined numerically using a calibrated, unstructured, finite volume numerical model （FVCOM）. Both wind direction and magnitude were determined to influence plume dispersal. Northeasterly （downwelling-favorable） winds drove fresh- water down-shelf while southeasterly （onshore） winds drove water up-shelf （in the sense of Kelvin wave propagation） , and were confined near the coast. Southwesterly （upwelling-favorable） and northwesterly （off： shore） winds transport more freshwater offshore. The transport flux is decomposed into an advection, a vertical shear, and an oscillatory component. The advection flux dominates the freshwater transport in the coastal area and the vertical shear flux is dominant in the offshore area. For the upwelling-favorable wind, the freshwater transport becomes more controlled by the advection transport with an increase in wind stress, due to enhanced vertical mixing. The relative importance of wind forcing and buoyancy force was investigated. It was found that, when the Wedderburn number is larger than one, the plume was dominated by wind forcing, although the importance of wind varies in different parts of the plume. The water column stratification decreased as a whole under the prevailing southwesterly wind, with the exception of the up-shelf and offshore areas.

Causes and Laws of Floods in Small and Medium Rivers in Jiangxi Province

The main causes of floods in small and medium rivers in Jiangxi Province are meteorological factors,rainstorm factors and topographic factors.Based on the data of more than 600 floods from 19 hydrological stations in small and medium rivers in Jiangxi Province,the characteristics of floods in small and medium rivers are analyzed. The results show that the floods in small and medium rivers in Jiangxi Province had characteristics of strong seasonality,high frequency and strong suddenness,and were mainly local floods;rainstorm floods during May-June lasted for a long term,and had double peaks,multi-peaks or a single peak with a long duration. During July-September,floods usually had a single peak,and the duration was relatively short.

Sources and distributions of terrigenous organic matter in a mangrove fringed small tropical estuary in South China

The sources and distributions ofterrigenous organic matter （OM） were investigated in a small tropical estu- ary in the Hainan Island, South China. Plants, suspended particulate matter （SPM）, and surface sediments samples in the estuary and coast were collected. Bulk properties [organic carbon （OC%）, total nitrogen （TN%）, stable carbon isotope （613C） and grain size] and lignin phenol concentrations were measured. OC% of mangrove plants was （43.44-2.1） %, which is similar to the values reported for mangrove plants in other re- gions. OC% of sediment samples ranged from 0.07% to 1.42%, and theywere related to the sediment texture. Lignin phenols in the sediment ranged from 5.16 rag/100 mg OC in the uppermost station to 0.51 mg/100 mg OC in the coast. The molar ratio of organic carbon to total nitrogen （C/N） （~7） and 613C （^-31.1 ~ 10-a） of riverine SPM revealed that the major OM sources of riverine SPM were aquatic OM （phytoplankton and/or bacteria）. Moreover, the lower lignin concentration （AS） and higher （Ad/A1）v of lignin phenols suggest that terrestrial OM in riverine SPM were mainly from soil. Furthermore, C/N ratio, 6 ~a C and lignin phenols reveal that mangrove plants were the predominant OM sources of mangrove surface sediment. Based on the 61aC and lignin phenols, it can be concluded that the major OM sources in estuarine and coastal surface sedi- ments were marine phytoplankton, riverine SPM and mangrove surface sediment. In addition, the higher （Ad/A1）v of lignin phenols in those coastal sediments indicate that seagrass might be a potential OM source in coastal sediments, however, the lower （Ad/A1）v in the estuarine sediments in turn suggests that seagrass could not be transported to the mangrove fringed region. A three-end-member model which is based on lignin concentrations and 6 I3C was applied to evaluate the contribution of mangroves to the organic matter preserved in the surface sediments. Around the mangrove fringed region, mangrove could contribute more than 50% to the sedimentary OM, and this value is much higher than riverine OM. Nevertheless, mangrove OM could not be efficiently transported to the coastal region. Our study suggests that mangrove forest is an important OM source in this small estuary.

RESEARCH ON SYSTEM OF FLOOD DISASTER CONTROL AND REDUCTION SUPPORTED BY GIS IN MEDIUM AND SMALL BASINS

Southeast China coastal areas belong to subtropical monsoon climatic zone, thus easily affected by floods resulted from typhoons and rainstorms. Since the areas of river basins are small, rivers flood regulation capacities are low, and therefore flood hazard is grave. In this paper, taking the Yongjiang basin in southeast China as an example, the approaches and methods of geographic information system(GIS) applied to flood disaster control and reduction research on small basin are explored. On GIS help the rainfall runoff calculation model and the river channel flood routing model are developed. And the evaluating flood submerged area and the damage assessment models are built supported by digit elevation models. Lastly the decision support system on GIS supported for flood control in research basin has been set up. This greatly improves flood proofing decision making capacities in river basin, and provides valuable information and a mode for flood prevention and reduction in the medium and small basin. Meanwhile, the research indicates that technologies of GIS provide a powerful tool for flood disaster control.

THE PLANNING AND MANAGEMENT INFORMATION SYSTEM FOR SMALL TOWN (TOWNMIS)——A CASE STUDY AT XIAOLAN TOWN, SOUTH CHINA

Now, GISs are popular at most major cities along the coast in China. The lack of available digital geographic data is a serious bottleneck problem. This article first analyses the development characteristics of urban planning and management information system in China, and proposes a method for establishing a planning and management information system for small town. By using GIS as core and integrating with microcomputer network, office automation (OA), computer aided design (CAD), and multimedia technology, a microcomputer information system (TownMIS) is implemented after 3 year design and development. It may be a first comprehensive system for the planning and management of small towns. Since the January of 1996, TownMIS has been actually used in Xiaolan Town, a coastal rich town in South China. This has provided perfect technical, managerial, operational and institutional references for resolving the contradiction of the fast growing installation of GIS sites and fewer actually running system.

Why Does the Repaired Len Small Levee, Alexander County, Illinois, US Continue to Breach during Major Flooding Events?

One only needs to study the soil and geologic history and location of the ancient Mississippi and Ohio Rivers to understand why Len Small levee if patched will continue to fail. Much of Dogtooth Bend located in Alexander County, Illinois was originally in the ancient Ohio River valley (Figure 1) alluvial sediments north and east of the confluence with the ancient Mississippi River. The ancient Ohio River valley soils underlain by alluvial sediments and have been easily eroded by the re-aligning modern Mississippi River which now travels through the bedrock controlled Thebes Gap (Figure 2) and into the Ancient Ohio river valley. The primary objectives of this paper are: 1) to explain why Len Small levee, Alexander County, Illinois, US will continue to breach during major flooding events if repaired and 2) to develop a new combined raised causeway and levee system which will provide a Mississippi River floodwater bypass, be sustainable, encourage and fund a land use change, restore the degraded highway road beds, protect remaining Dogtooth Bend farmsteads and farmland that have not yet been degraded by past flooding events and provide floodwater storage during major flooding events at the confluence of the Mississippi and Ohio Rivers.

基于HS-Small模型临江深基坑降水变形特性分析

临江深基坑工程地下水随江水位变化呈现长期水位低、汛期水位高的动态特征,坑内降水导致周围地层渗流场趋于复杂,易引发围护结构破坏、坑底管涌和基坑失稳等工程事故。为此,采用基于HS-Small本构模型对深基坑工程的开挖-降水过程进行模拟,分析了降水影响因素(降水深度、方式、速率和止水帷幕)对周围环境变形的敏感性及其相互之间的关系,并将分析结果与实测结果进行对比验证。结果表明,随临江深基坑土方开挖和降水进行,基坑坡顶、坑外土体和周边建筑物沉降变形逐渐增大,其中降水对基坑变形影响更明显;分次降水能有效降低周围建筑物和地表的沉降变形;降水深度建议控制在底板以下0.5~2.0 m;降水速率对周围环境沉降总量影响相对较小,但对沉降速率影响较大,当降水速率达到最优值时对基坑稳定性控制有益;止水帷幕嵌入深度超过30 m后对控制周围建筑沉降效果不明显。研究结果可为类似临江深基坑降水工程设计施工提供借鉴和参考。

基于长短时记忆网络的山区中小流域降雨径流模拟

洪水预报是流域防洪减灾的重要非工程措施之一。目前我国中小河流暴雨洪水灾害频发,但应对短历时强降雨的洪水预报能力仍不强。以安徽省东部山区中小流域为研究对象,引入长短时记忆网络建立流域降雨径流模型,探讨其在山区中小流域的洪水模拟效果。结果表明,考虑降雨输入的空间差异可提升深度学习模型降雨径流模拟预测性能,且长短时记忆网络能够取得优于传统人工神经网络的精度;长短时记忆网络模型有效建立了流域降雨与径流间的复杂非线性关系,模型在所选流域内场次洪水的峰值模拟效果较好,训练、测试集场次洪水峰值合格率均在90%以上;长短时记忆网络内部结构特征与流域水文过程具有较好的相似性,对山区中小流域暴雨洪水非线性关系拟合效果突出。

数字素养对小农户衔接现代农业的影响研究——基于黄河流域9省区1592户小农户的调查

基于黄河流域9省区1592户小农户的调研数据,利用LPM和Probit模型分析数字素养对小农户衔接现代农业的影响。结果表明:数字素养的提升能够促进小农户衔接现代农业;机制分析发现,数字素养通过拓宽小农户信息获取渠道、提高小农户信息获取能力来影响小农户衔接现代农业;引入ESRM模型结合反事实推断分析发现,数字素养提升可以使小农户衔接现代农业的水平提高45.33%;小农户数字素养对地理邻近农户衔接现代农业的行为具有正向空间溢出效应;异质性检验发现,数字素养对衔接现代农业的影响在纯小农户中最大,其次是兼业型小农户,数字素养对中低收入小农户衔接现代农业的影响要大于高收入小农户。根据结论,提出加强对小农户的数字化培训和指导以提升其数字素养,对不同类型小农户有针对性地提供帮扶措施,通过示范效应带动周边小农户衔接现代农业等政策建议。

水土保持碳汇项目管理信息系统的开发探索

水土保持碳汇项目信息化管理可以为水土保持碳汇项目开发提供科学规范的技术手段。分析了水土保持碳汇项目管理信息系统开发的主要挑战、建设目标及总体框架,以福建省长汀县罗地河小流域综合治理水土保持碳汇开发为研究对象,探索水土保持碳汇项目开发的全过程信息化体系建设,总结了系统在罗地河小流域综合治理过程中的应用情况以及存在的不足,并提出相关建议,以期为提升水土保持碳汇项目管理水平提供借鉴参考。

小区域尺度视角下的丽江市玉河健康特征研究

随着社会发展,工业化、城镇化进程不断加快,河湖生态问题日益突出且呈现更复杂的发展态势,进行河湖健康评价,开展河湖健康问题诊断,针对性地提出河湖生态系统精准治理、生态修复与保护等对策显的尤为迫切.结合丽江市典型河流玉河,以水域岸线状况、水量水质状况、生物状况、社会服务功能等4个准则层为重要抓手,构建11个指标层的河流健康评价体系,将玉河划分为农村段、城镇段、复合段3个小区域尺度进行综合评价,探讨了小区域尺度河流健康评价差异性特征,研究表明:玉河全河段、各分段均处于亚健康状态,玉河农村段、复合段、各城镇段岸线部分指标层、准则层间健康状况差异性显著,主要存在水资源禀赋差,生态流量小,底栖动物少,局部岸线状况较差的问题.

黄河流域中小河流水质评价的比较研究

我国中小河流众多,流域面积覆盖了全国85%的城镇及广大农村地区,是区域生产生活用水的主要来源和污染负荷排放的接纳者.开展中小河流水质综合评价对于客观、准确地评价水环境质量状况,制订水污染防治整体规划具有重要意义.以黄河流域河南省2条典型中小河流为研究对象,在识别河流水污染状况的基础上,采用单因子评价法、综合污染指数法、水质标识指数法和模糊综合评价4种方法对水质现状进行了综合评价,探讨了不同方法在中小河流水质评价中的适用性.结果表明:2条中小河流主要污染指标为NH_(3)-N、挥发酚及TP;水质标识指数法的评价结果与可靠性分析中的水质评价结果一致性最高,该方法得到的水质类别结果更加可靠.

概念性水文模型与智能模型在中小河流洪水模拟中的比较研究

相较于大江大河的流域水文预报研究,中小流域的研究相对匮乏。以沅江河溪水文站以上流域为例,研究LSTM(Long Short-Term Memory)模型和新安江模型在场次洪水中的模拟效果。通过对比,新安江模型的整体模拟精度较高,洪量、洪峰、峰现时间的平均相对误差分别为9.39%、9.55%、1.6h,确定性系数为0.73,综合合格率为100%,达到甲级精度标准;LSTM模型的模拟精度较低,洪量、洪峰、峰现时间的平均相对误差分别为11.76%、12.33%、2.3 h,确定性系数为0.60,综合合格率为75%,达到乙级精度标准。结果表明,新安江模型和LSTM模型是中小河流洪水预报的有效方法,均可用于河溪流域的正式预报,且对于河溪流域,新安江模型的模拟精度比LSTM模型更高。

广东省沿海平原中小河流淹没图编制方法初探

广东省沿海平原中小河流具有比降缓、潮汐影响大、淹没范围广和堤围密集等特点,其淹没图编制至今无统一方法。该文通过Mike21和Arcgis软件,结合河流特性,参考《山丘区中小河流洪水淹没图编制技术指引》,以乌坎河为例探求出一种适用于广东省沿海平原中小河流的淹没图编制方法。该方法具有可操作性强、准确性较高和适用范围较广等特点,为后续广东省沿海平原中小河流淹没图制作提供参考。

沿海中小河流域地表-地下水库联合调控洪水资源利用研究:Ⅰ.方法与模型

针对沿海中小河流域地表-地下水库复杂工程系统,因缺少联合调控方法而导致洪水资源利用难的问题,解析地表-地下水库系统结构与功能,定量模拟地表水库调度、闸坝调控下河流和地下水动力过程,并利用智能替代模型提升水动力过程计算速度;在此基础上通过研发时/日/月多时间尺度模型耦合嵌套方法,构建了兼顾计算精度与效率的地表-地下水库联合调控模型。该模型实现了洪水、地表-地下水相互作用和供水等时间尺度差异明显的调节过程的统一调配,可为沿海中小河流域洪水资源利用提供新思路与技术支撑。

夏县红沙河片区生态清洁小流域综合治理

红沙河片区存在河源区保护力度弱、沟道水系连通状况差、水资源和土地资源利用率低、农村基础设施差等问题。通过在预防保护区进行封禁治理,综合治理区布置坡改梯工程、保土耕作、林草工程、泉水利用工程等水保工程,同步推进面源污染防治、人居环境整治和文旅工程建设,生态修复区对赤峪河、吴家峪沟进行沟槽整治、边坡治理、岸边绿化等措施,将片区建设成为生态旅游型生态清洁小流域,可完善区内农业灌溉设施,提高了区内泉水利用率、土地生产力及沟道行洪能力,可有力促进当地特色产业、特色旅游业的发展,实现山青、水净、村美、民富的目标。工程建设亦可为同类工程建设提供借鉴和参考。