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1.
The mouth of the Vistula River, which is a river outlet located in tideless area, is analyzed. The Vistula River mouth is a man-made, artificial channel which was built in the 19th century in order to prevent the formation of ice jams in the natural river delta. Since the artificial river outlet was constructed, no severe ice-related flood risk situations have ever occurred. However, periodic ice-related phenomena still have an impact on the river operation. In the paper, ice processes in the natural river delta are presented first to refer to the historical jams observed in the Vistula delta. Next, the calibrated mathematical model was applied to perform a series of simulations in the Vistula River mouth for winter storm condition to determine the effects of ice on the water level in the Vistula River and ice jam potential of the river outlet.  相似文献   

2.
Turutin  B. F.  Matyushenko  A. I. 《Water Resources》2001,28(2):224-228
The effect of different factors on the duration of spring ice jams and the flood water level in the Siberian rivers is considered. Observational data on the frequency of ice jams of different probabilities within some reaches of the Yenisei River are presented.  相似文献   

3.
Variations in the characteristics of ice regime of rivers in the Northern Dvina basin over the last 125 years are analyzed. For the Northern Dvina lower course, potential changes in the dates of the appearance of floating ice and the breakup due to expected changes in the air temperature and the rate of streamflow in rivers are assessed. Special attention is paid to the factors that affect the formation of ice jams and their spatial and temporal variability. The prognostic relationship for the maximum ice-jam stage in the Sukhona River near the town of Velikii Ustyug is presented as an example.  相似文献   

4.
《水文科学杂志》2013,58(3):450-464
Abstract

On the basis of analysing the genesis, recurrence and severity of flood hazards, a regional flood hazard analysis of the southern area of East Siberia has been carried out. The greatest flood hazard corresponds to the relatively densely populated area of southern East Siberia: the Upper Yenisei, Angara and Upper Lena river basins and the Lake Baikal watershed. Typically, the most hazardous floods include those caused by surges produced by damage to the dams of the Angara—Yenisei hydropower cascade; flash floods are also an extreme hazard. Maximum runoff factors were used to delineate regions within the study area, and the hazard severity was scored for the Irkutsk region. An inventory of the ice-dam and ice-jam areas, as well as of the streamflow sites with maximum runoff of different origins predominating in the Angara and Lena river basins, showed that the study area includes 78 and 19 ice-dam and ice-jam locations, respectively. A high recurrence of ice dams and ice jams is also observed on other rivers.  相似文献   

5.
The basic peculiarities of the hydrological regime of one of the largest mouth areas of the world, i.e., the common mouth of the rivers of Ganges and Brahmaputra, are discussed. The main features of natural conditions (including climatic) of the mouth of these rivers and the delta drainage system are characterized. The hydrological regime of the Ganges and Brahmaputra rivers, the largest rivers of South Asia, is studied in greater detail; the quantitative assessments of the water and sediment runoff of these rivers are specified. Provision is made for revealing the basic peculiarities of river flow distribution among numerous delta branches, annual floods during southwest monsoons, tidal phenomena in the maritime zone of the delta, and disastrous storm surges and inundations in the period of tropical cyclones. Flood control measures taken in Bangladesh to protect the population and lands are described.  相似文献   

6.
A large number of rivers are frozen annually, and the river ice cover has an influence on the geomorphological processes. These processes in cohesive sediment rivers are not fully understood. Therefore, this paper demonstrates the impact of river ice cover on sediment transport, i.e. turbidity, suspended sediment loads and erosion potential, compared with a river with ice‐free flow conditions. The present sediment transportation conditions during the annual cycle are analysed, and the implications of climate change on wintertime geomorphological processes are estimated. A one‐dimensional hydrodynamic model has been applied to the Kokemäenjoki River in Southwest Finland. The shear stress forces directed to the river bed are simulated with present and projected hydroclimatic conditions. The results of shear stress simulations indicate that a thermally formed smooth ice cover diminishes river bed erosion, compared with an ice‐free river with similar discharges. Based on long‐term field data, the river ice cover reduces turbidity statistically significantly. Furthermore, suspended sediment concentrations measured in ice‐free and ice‐covered river water reveal a diminishing effect of ice cover on riverine sediment load. The hydrodynamic simulations suggest that the influence of rippled ice cover on shear stress is varying. Climate change is projected to increase the winter discharges by 27–77% on average by 2070–2099. Thus, the increasing winter discharges and possible diminishing ice cover periods both increase the erosion potential of the river bed. Hence, the wintertime sediment load of the river is expected to become larger in the future. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

7.
The lower stretch of the Vistula is the most ice‐jammed river section on the North European Plain. Since 1982, the structure of hanging dams has been studied by means of a mechanical non‐core sampler. In this article, a selected of field research results of the hanging dams' structure and the degree of filling of the cross section with ice obtained during surface ice‐jam events in the years 1995–2014 are presented, along with an explanation of their causes. Surface ice jams occurred during spring snowmelt surges and ice breakups and also during freeze‐up and ice‐covered periods. Their main cause was changes in the river flow and was also those affected by anthropogenic sources. A characteristic feature of the analysed cross sections was the considerable share of the underhanging ice dam's firm accumulation with ice floes, when the cross section would be filled with ice in excess of 70%. In most cases, due to low river discharge, there was no substantial flooding damage. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

8.
This study documents the spatiotemporal variations in the frequency and magnitude of ice jams in the Mistassini River and applies that information to the identification of the hydro‐climatic threshold conditions associated with major events. Ice jams cause severe upheavals in water flow, which result in flooding upstream of the ice jam front, and therefore represent a significant geohazard to riparian populations. To analyze the spatiotemporal variations in the magnitude–frequency of ice jams, the Mistassini River was first divided into six different sites representing different geomorphological contexts. A 50‐year ice jam chronology was constructed from 85 damaged trees from all of the study sites. This chronology was then coupled with hydro‐climatic variables to construct classification trees, which helped identify the conditions and hydro‐climatic thresholds favourable to the triggering of ice jams in a predictive model. The results indicate complex interactions between the characteristics of flow, ice cover and river morphology that affect the frequency and magnitude of ice jam events on the Mistassini River. These factors affect the frequency and magnitude of ice jam events. The triggering of extreme events seems particularly influenced by exceptional ice conditions and sites with high sinuosity and islands. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
The evolution of the Ganges and Brahmaputra river delta during the Holocene period is discussed. Particular attention is given to the processes of delta formation, the dynamics of the delta hydrographic systems, the channel processes in river branches, as well as to the dynamics of the delta coastline and nearshore zone bed over the last 150–200 years. The calculation of sediment budget in the mouth area of these rivers is presented.  相似文献   

10.
Data on the Colville River mouth (Alaska, USA) are used to discuss the regularities in hydrological processes taking place in river mouth areas, functioning under extreme arctic conditions. Seasons and periods are recognized in the annual cycle of the Colville river mouth hydrologic regime. A thick ice cover commonly forms in winter in the river, its delta distributaries, and the offshore zone. Water salinity in under-ice water in the distributaries and near-delta river reach appreciably increases in late winter. The spring flood is very short; in this period, snowmelt water propagates toward the ocean first over ice and next under it. A wedge of freshened waters forms in the nearshore zone above fast ice. River runoff abruptly drops in the summer-autumn low-water period. The morphological processes in the distributaries and some ecological conditions in the delta are also discussed.  相似文献   

11.
Water and sediment dynamics at Saint Lawrence River mouth   总被引：1，自引：0，他引：1  
The main features of the hydrological regime and morphological structure of the estuarine-type mouth area of the Saint Lawrence River are considered. Data on the structure of water masses, thermal and ice regimes in the Gulf of Saint Lawrence, which has a significant effect on the estuary, are given. The major attention is paid to water mixing processes, water and sediment dynamics in the estuary under the joint effect of river runoff and tides, and as a function of bed topography. The parameter determining the type of water stratification and circulation is discussed. The effect of the Coriolis force on the stratified flow in the estuary and formation of the geostrophic current is discussed.  相似文献   

12.
Porosity, or void space, of large wood jams in stream systems has implications for estimating wood volumes and carbon storage, the impacts of jams on geomorphic and ecological processes, and instream habitat. Estimating porosity and jam dimensions (i.e. jam volume) in the field is a common method of measuring wood volume in jams. However, very few studies explicitly address the porosity values in jams, how porosity is calculated and assessed for accuracy, and the effect such estimates have on carbon and wood budgets in river corridors. We compare methods to estimate jam porosity and wood volume using field data from four different depositional environments in North America (jam types include small in-channel jams, large channel-margin jams, a large island apex jam, and a large coastal jam), and compare the results with previous studies. We find that visual estimates remain the most time-efficient method for porosity estimation in the field, although they appear to underpredict back-calculated porosity values; the accuracy of jam porosity, and thus wood volume, estimates are difficult to definitively measure. We also find that porosity appears to be scale invariant, dictated mostly by jam type, (which is influenced by depositional processes), rather than the size of the jam. Wood piece sorting and structural organization are likely the most influential properties on jam porosity, and these factors vary according to depositional environment. We provide a framework and conceptual model that uses these factors to demonstrate how modeled jam porosity values differ and give recommendations as a catalyst for future work on porosity of wood jams. We conclude that jam type and size and/or the study goals may dictate which porosity method is the most appropriate, and we call for greater transparency and reporting of porosity methods in future studies. © 2020 John Wiley & Sons, Ltd.  相似文献   

13.
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14.
Climate change is altering river temperature regimes, modifying the dynamics of temperature‐sensitive fishes. The ability to map river temperature is therefore important for understanding the impacts of future warming. Thermal infrared (TIR) remote sensing has proven effective for river temperature mapping, but TIR surveys of rivers remain expensive. Recent drone‐based TIR systems present a potential solution to this problem. However, information regarding the utility of these miniaturised systems for surveying rivers is limited. Here, we present the results of several drone‐based TIR surveys conducted with a view to understanding their suitability for characterising river temperature heterogeneity. We find that drone‐based TIR data are able to clearly reveal the location and extent of discrete thermal inputs to rivers, but thermal imagery suffers from temperature drift‐induced bias, which prevents the extraction of accurate temperature data. Statistical analysis of the causes of this drift reveals that drone flight characteristics and environmental conditions at the time of acquisition explain ~66% of the variance in TIR sensor drift. These results shed important light on the factors influencing drone‐based TIR data quality and suggest that further technological development is required to enable the extraction of robust river temperature data. Nonetheless, this technology represents a promising approach for augmenting in situ sensor capabilities and improved quantification of advective inputs to rivers at intermediate spatial scales between point measurements and “conventional” airborne or satellite remote sensing.  相似文献   

15.
To deal with the accidental release of pollutants into frozen rivers, those rivers in high-latitude regions should be treated differently. Pollutants could be stored up in the ice and released when the ice melts in spring, perhaps resulting in secondary pollution in the river. A water quality model of nitrobenzene has been developed in this paper to assess the influence on river water quality due to the freezing process. The model is made up of three modules: thermodynamic module, hydrodynamic module and water quality module. The thermodynamic module considers the complex heat exchange processes between the water body and the atmosphere, the water body and the river bed, the water body and the ice cover, and so on. The growth of the ice cover is simulated in a simplified form whilst taking consideration of heat balance. The hydrodynamic model uses the Saint-Venant equations in non-constant flow and the influence of the ice cover is measured. The degradation, diffusion, absorption and desorption, and the influence of the freezing process are incorporated in the water quality module and the concept of Continuously Stirred Tanked Reactors (CSTRs) model is applied in the model construction. The model has been applied to supporting the management of accidental pollution in the Songhua River. The model was calibrated and validated with monitored data. Regional sensitivity analysis based on a task-based Hornberger-Spear-Young (HSY) algorithm was carried out to examine the model structure and the result showed that the model could describe the system very well. Then the conditioned model was applied to predicting the concentration of nitrobenzene in the water when the ice melted in spring. The predictive result showed that the release of pollutants in the ice could lead to an increase in the concentration of pollutants in the water, but the increase would be very small because there was only a small amount of pollutants stored in the ice. A secondary pollution could therefore be avoided. Also, with necessary modifications, the model established in this study could be applied to the water quality management in rivers that freeze in winter.  相似文献   

16.
Water and sediment qualities are studied by analyzing samples taking from the mouths of the Haihe, Duliujian, New Ziya and Beipai rivers in the Haihe river basin in north China in 2005 and 2001, in order to find the changes of water and sediment pollutions. The concentrations of heavy metals, arsenic, total nitrogen (TN) and total phosphorus (TP) are analyzed and results have been compared for the two times. The in-situ measurement for Dissolved Oxygen (DO) and Sediment Oxygen Demand (SOD) rates were carried at the Haihe and Duliujian river mouths in 2006. The results show that the waters of the 4 river mouths are still seriously polluted, though much improved in the case of the Haihe and Duliujian rivers. The main pollutants are TP and TN in the New Ziya and Beipai rivers and mercury (Hg) at all 4 river mouths. Compared with those in 2001, the concentrations of almost all metals and arsenic in the 4 river mouths have decreased. Water quality at Haihe and Duliujian shows an improving trend, while the water quality at Beipai is similar to that of 2001. In contrast, water at the New Ziya river mouth is more severely polluted. The sediments in the 4 river mouths are not seriously polluted by heavy metals but are polluted by nitrogen and phosphorus. Most of the pollutant contents in the sediments show little change between 2001 and 2005. The in-situ DO and SOD measurement shows that the waters at the Haihe river mouth is in the state of oxygen depletion, and SOD is important consumer of DO at the river mouths. The overall analysis shows that increasing water pollution and eutrophication in waters far from cities are ongoing causes of concern.  相似文献   

17.
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18.
This study describes the formation of two successive baymouth spits systems on the south‐eastern Brazilian coast and the degradation of the first system. The study area includes the Jureia Beach spit, the deflected Ribeira de Iguape River mouth, the central Iguape sandy headland, the Icapara Inlet of the Mar Pequeno Lagoon and the northern end of the Comprida Island barrier spit. The wave and river flow patterns were combined with the coastline evolution and the alongshore migration rates deduced from satellite images. Initially, both spits showed convergent alongshore migration rates equal to or less than 83 m/yr. However, the extreme river flow due to high rainfall during a very strong El Niño event in 1983 eroded the inland side of the Jureia Beach spit, which finally retreated due to wave erosion. In 1989, a sand bank emerged in the river mouth, which attached to the central headland forming a recurved northeastward spit. In 1994, the high fluvial discharge associated with another very strong El Niño event caused the landward migration of the new spit and emersion of a second sand bank. This second sand bank merged with the Jureia Beach spit in 1997 at an alongshore migration rate of 1795.6 m/yr. Wave erosion of the central headland continued and the attached spit disappeared in 2000. In 2009, the headland erosion merged the river mouth and the Icapara Inlet, which resulted in flanking baymouth spits in a configuration that remains today. Therefore, two models for the formation of baymouth spits have been documented for wave‐dominated microtidal coasts in humid tropical regions with intense fluvial discharge. The convergent longshore migration of the spits is controlled by both the bidirectional longshore drift and the fluvial discharge, the latter eroding the fronting spit, supplying sediments and acting as a hydraulic blockage for longshore drift. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

19.
The results of studying the ice regime in Transbaikalian rivers and its dependence on climate change are given. The magnitudes of many-year changes in the dates begin and end of freeze-up period, its duration, and maximal ice thickness are determined. The dependence of major characteristics of ice regime on air temperature and river runoff is evaluated.  相似文献   

20.
Reliable and prompt information on river ice condition and extent is needed to make accurate hydrological forecasts to predict ice jams breakups and issue timely flood warnings. This study presents a technique to detect and monitor river ice using observations from the MODIS instrument onboard the Terra satellite. The technique incorporates a threshold‐based decision tree image classification algorithm to process MODIS data and to determine the extent of ice. To differentiate between ice‐covered and ice‐free pixels within the riverbed, the algorithm combines observations in the visible and near‐infrared spectral bands. The developed technique presents the core of the MODIS‐based river ice mapping system, which has been developed to support National Oceanic and Atmospheric Administration NWS's operations. The system has been tested over the Susquehanna River in northeastern USA, where ice jam events leading to spring floods are a frequent occurrence. The automated algorithm generates three products: daily ice maps, weekly composite ice maps and running cloud‐free composite ice maps. The performance of the system was evaluated over nine winter seasons. The analysis of the derived products has revealed their good agreement with the aerial photography and with in situ observations‐based ice charts. The probability of ice detection determined from the comparison of the product with the high‐resolution Landsat imagery was equal to 91%. A consistent inverse relationship was found between the river discharge and the ice extent. The correlation between the discharge and the ice extent as determined from the weekly composite product reached 0.75. The developed CREST River Ice Observation System has been implemented at National Oceanic and Atmospheric Administration–Cooperative Remote Sensing Science and Technology Center as an operational Web tool allowing end users and forecasters to assess ice conditions on the river. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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