Small Size River Research Articles

Investigation of compound occurrence of storm surge and river flood in Mikawa Bay, Japan, using typhoon track ensemble experiments

The risk of high river flow and peak storm surge superimposing in the estuary of small-and medium-sized rivers can be more severe during typhoon landfalls than at other times. In this study, 30 cases of typhoon track ensemble experiments for five rivers in Mikawa Bay, Japan, were evaluated using an atmospheric-river-ocean model. The results showed that storm surges coincided with high river flows when typhoons crossed the western side of Mikawa Bay, with the highest potential observed when typhoons passed northwest of the Bay. The average time discrepancy for the five rivers between the storm surge occurrence and increased river flow in the minimum time difference case was 48 min at the river mouth. Distinct trends in the time difference between a storm surge and river flow were observed for each river mouth. The order of time differences corresponded to the drainage area scale: Toyo (188 min), Umeda (112 min), Otowa (114 min), Sana (96 min), and Yagyu (88 min). Time difference trends also varied based on the distance between the typhoon center and each river mouth. For Toyo River, storm surges and high river flows did not substantially overlap, regardless of distance. However, for medium-and small-sized rivers, the time difference increased proportionally with the distance from the typhoon. The Yagyu River showed the highest potential for compound occurrence of a storm surge and river flood because of the synchronization of storm surge peaks and high river flow peaks, with a time difference of 1–2 h for small-and medium-sized rivers within 100 km2 of the basin.

SPATIAL ESTIMATION OF SOIL EROSION USING GEOSPATIAL TECHNIQUE – A CASE STUDY OF JANJEVA RIVER CATCHMENT (KOSOVO)

The aim of the study is to analyse the spatial estimation of soil erosion in a small size river catchment of Janjeva (Kosovo). Soil erosion is becoming a serious threat and its spatial estimation is crucial for soil resource protection and management. The Revised Universal Soil Loss Equation (RUSLE) methodology integrated with GIS techniques was applied to estimate the annual erosion rate. Different datasets including open-source data were used to find main components of soil erosion. The results show different soil erosion classes depending on lithological settings, landforms, climate conditions, soil properties, land cover and soil conservation practices. By calculating RUSLE parameters for Janjeva River catchment (84 km²), we found out that mean annual erosion rate is 1 t·ha-¹·yr-¹. Erosion rate class <5 t·ha-¹·yr-¹ dominates the catchment’s area with 92.5%, while other classes have 7.5% of catchments total area. Highest rates of soil erosion are found in volcanic rocks, steep slopes and soils without conservation practices. Soils located in western part of the catchment with adequate conservation practice have minimum erosion rate.

Small Hydro Plant Developments

The exploitation of the renewable sources is a challenge for all the engineers. Hydro power application is ranging from a kW to order of GW. The technical solutions have a wide spectra, such as turbines and dam constructions. The hydro power potential of Hungary is modest. Óbuda University cooperates with the patent owner in the development of new devices. In this paper we introduce the latest development for the mini hydro applications capable of deploying low heading watercourses and small size rivers. The fast mountable flowing through arrangement and the anchored floating Sagebien wheel devices have 5-10 kW output power. These days the operations are in the test phase.

Lateglacial to Middle Holocene landscape development in a small-sized river valley near Antwerp (Belgium)

At the transition between the Scheldt valley and the Campine microcuesta near Antwerp, two separate organic deposits are present in the subsoil. Sedimentological, macrobotanical and palynological analyses from two cores are used to reconstruct the evolutions of the local depositional and ecological environment, as well as the regional vegetation. An age-depth model based on radiocarbon dates allows to frame those evolutions chronologically. During the Weichselian lateglacial, a mesotrophic lake was filled with peat during GI-1. The sand input indicates continued aeolian activity, also during forested phases. This peat was covered by wind deposits during GS-1. From the start of the Holocene onwards, a river channel in the Opstal Valley started to fill with peat in a mesotrophic fen. Pollen records show a temporary opening of the regional forest, that can be linked to the 11.4 ka event. The peat dried out around 11,000 cal BP and wetter conditions returned by the beginning of the Middle Holocene, with the development of an alder/birch carr. Unlike the Scheldt valley, the Opstal valley was not under tidal influence in the Middle Holocene. After ca. 6000 cal BP, the valley was part of the coastal peatlands that evolved from mesotrophic fen into oligotrophic bog.

Assessment of GRACE/GRACE Follow-On Terrestrial Water Storage Estimates Using an Improved Forward Modeling Method: A Case Study in Africa

Leakage errors derived from spatial filters are the major limitation for estimating terrestrial water storage via the Gravity Recovery and Climate Experiment (GRACE) mission and the recently launched GRACE Follow-On mission. Here we develop an improved forward modeling method and assess its performance of reducing leakage errors over Africa. In noise-free condition, the forward modeling method shows its outperformance in restoring signals, and the improved forward modeling method can further reduce the leakage errors along the coastline of Africa. In noise-contaminated condition, the simulated environment is set as real as possible to GRACE mission and GRACE Follow-On mission. The results based on the simulated GRACE and GRACE Follow-On solutions demonstrate the capacity of improved forward modeling method in reducing leakage errors. In the case of simulated GRACE data, the average improvements of 24 basins over Africa are respectively 37% for annual amplitudes and 36% for trends. When compared with these simulated GRACE data, the improvements via simulated GRACE Follow-On solutions are minor over large and medium size river basins, but they are significant over small size river basins. In the case of simulated GRACE Follow-On solutions, the average improvements over Africa are 39% for annual amplitudes and 41% for trends. Eventually, the improved forward modeling method is used to process GRACE spherical harmonic datasets from the Center for Space Research (CSR). The results present better agreement with those derived from the newly released mascon solutions from Jet Propulsion Laboratory (JPL) and CSR, when compared with those derived from CSR Tellus grids with scale factors. The better consistency between these model-independent approaches indicates the good performance of our improved forward modeling method and the further necessity of careful evaluation of model-dependent approaches when using different prior hydrological models. Overall, experiments based on noise-free observations, noise-contaminated observations, and GRACE datasets indicate that improved forward modeling method is capable of restoring temporal signals.

Floating Garbage Collector Based on OpenMV

Due to the high cost of human labor for maintenance, garbages in rivers often do not receive immediate cleaning, resulting in severe water pollution. Those floating garbages simultaneously strip the aesthetic of rivers and threaten the local marine ecosystem. Thence, we developed an unmanned vessel based on Arduino’s platform, capable of auto-collecting garbage. The vessel includes two modes: the human operational mode allows individuals to manipulate the vessel and to collect garbages through Bluetooth connection; the auto-collecting mode is based on OpenMV’s video processing function, enabling vessels to detect garbages nearby and transport the garbages into the vessel’s interior through a rotating caterpillar track. At the end of this project, the vessel remains large rooms for improvements, such as increasing the efficiency and effectiveness of garbage collection and garbage detection. The vessel is suitable in small size rivers or ponds were artificial cleaning faces obstacles.

Spatiotemporal variations in chromophoric dissolved organic matter (CDOM) in a mixed land-use river: Implications for surface water restoration

A challenge for current surface water restoration and management in China is acquiring the source information for complex pollution scenarios in order to develop effective control strategies. As an important part of dissolved organic matter, chromophoric dissolved organic matter (CDOM) contains unique chemical signals related to various pollution sources. Spectral methods such as fluorescence excitation-emission matrices coupled with parallel factor analysis enable rapid and low-cost CDOM characterization for source tracking. In this study, a typical small-sized river flowing through mixed land-use regions in southeastern China, the Lujiang River, was investigated to determine the responses of CDOM to spatiotemporal factors. The effects of land-use patterns were reflected by the fluorescent components of terrestrial and sewage substances. A high and stable proportion of terrestrial-like components (C1 + C2) in each sampling period (i.e., March: 47.6 ± 5.7% and October: 44.3 ± 2.7%) indicated a high input of non-point source (NPS) pollution from both agriculture and urban areas. In addition, the difference in solar radiation intensity induced by climate and air quality changes was also reflected by variability in the photodegradation product component (C3) of terrestrial precursors between October (24.8 ± 2.6%) and March (4.5 ± 2.0%), suggesting that terrestrial components could be a sensitive indicator for NPS pollutant monitoring. Increased sewage impact in downstream regions was reflected by a spike in the tryptophan-like component (C4); temporal variations in C4 (paired t-Test, p < 0.005) also indicated that sewage substances were more prone to removal by microbial activity in warmer seasons. The dynamics of C4 could serve as a good indicator of sewage disposal performance. The results of this study demonstrate that CDOM data have important practical applications for existing water restoration campaigns in southeastern China, as well as substantial potential for routine water quality monitoring.

Факторы пространственной изменчивости речного стока в Центральной Якутии

Based on the analysis of the daily discharges for all active and recently closed hydrological posts at the small and medium-sized rivers of Central Yakutia, it was found that the mean annual runoff and its variation coefficient significantly vary although precipitation and evaporation values are relatively stable in space. Precipitation of previous years largely influences the river runoff formation of the current year. Small-sized rivers have a delayed runoff response to rainfall compared with the larger rivers of the region at the yearly and monthly time scale. The higher the proportion of alas-type type, that has many thermokarst lakes and depressions, the lower and less stable runoff (the variation coefficient is higher, the runoff duration is shorter). The higher the proportion of slope-type terrain, the higher the mean annual and maximum daily river runoff, as well as the longer runoff duration. The mean annual evaporation correlate with the share of the slope-type terrain. Many thermokarst depressions, that are typical for the alas-type terrain, cause a low flow presumably due to the absence of water discharge of thermokarst lakes and their local catchments into the river and increased evaporation from the lake surface. It was shown that the landscape factor has leading role in the runoff formation of the small and medium-sized rivers in Central Yakutia.

Relationship between physical environmental factors and presence of molluscan species in medium and small river estuaries

River estuaries are critical aquatic environments characterized by large environmental gradients in their water quality, riverbed material, and microtopography in the longitudinal and transverse directions. Molluscan fauna are sensitive to changes in water quality or bottom sediment conditions, and include species that inhabit unique environments or have a high capacity to thrive in different habitats. The interrelations between ecology and whole physical environment of molluscan fauna have rarely been studied, especially in medium and small sized river estuaries. This study was conducted to investigate the relationship between molluscan fauna and multiple hierarchical physical factors in river estuaries, and develop a prediction model for each of the molluscan species under study. The study focused on molluscan fauna in river estuaries in medium and small size rivers, where knowledge is particularly limited. Results obtained from quadrats were classified into three groups related to physical factors, including wave and river energy and habitat scale factors. Prediction models for molluscan species indicated that physical factors affected different species at varied scales. There were species influenced by watershed scale, habitat scale, or both. Because the physical factors influenced species at different scales, prediction of potential molluscan fauna on a site is also critical, in addition to the conservation or restoration of habitats.

Introduction to the production procedure of representative annual maximum precipitation scenario for different durations based on climate change with statistical downscaling approaches

Climate change has been influenced on extreme precipitation events, which are major driving causes of flooding. Especially, most of extreme water-related disasters in Korea occur from floods induced by extreme precipitation events. However, future climate change scenarios simulated with Global Circulation Models (GCMs) or Reigonal Climate Models (RCMs) are limited to the application on medium and small size rivers and urban watersheds due to coarse spatial and temporal resolutions. Therefore, the current study introduces the state-of-the-art approaches and procedures of statistical downscaling techniques to resolve this limitation It is expected that the temporally downscaled data allows frequency analysis for the future precipitation and estimating the design precipitation for disaster prevention.

Low-Intensity and Micropore Pipes Aeration Powered by Wind-Solar Energy in Treating Urban Black-Odour Rivers

Some effects had been gained in urban inner rivers treatment in recent years. But more medium and small size rivers in city were polluted much heavier because of their small flow, slow velocity and locating deep into the resident areas. The remediation of these rivers needed long and enduring investing and management and thus became the main restrict of the government. This paper according to this status, put forward to a new kind of river aeration model, which combined low-intensity aeration with micropore pipes aeration and powered by wind-solar energy street lamp system. Because of the effectiveness in removing pollutant and low energy consumption, this combined system supported important reference and a new study direction in treating the urban black-odour rivers enduringly.

A dataset of molluscan fauna sampled in river estuaries of medium and small size river in Kyushu island, Japan.

BackgroundMany studies have evaluated the ecological integrity of large-scale estuaries of continental rivers using biotic indicators such as fish, phytoplankton and benthic communities. However, few studies have focused on the river estuaries of small and medium rivers. Molluscan fauna data in large estuaries or in the estuaries of large rivers have been collected by the The National Census on River Environments (conducted by the Ministry of Land, Infrastructure, Transport and Tourism) or National Survey on the Natural Environment (conducted by the Ministry of Environment). On the other hand, molluscan fauna of small and medium rivers are managed by local governments and have rarely been investigated.New informationThis paper provides basic information on the molluscan fauna of 70 rivers in Kyushu, Japan, collected with the aim of conserving estuaries of small and medium rivers. In total, 37 families, 82 species and 21,827 individuals were collected. The data are all accessible from the document “A dataset of shellfish fauna sampled in estuaries of medium and small rivers in Kyushu, Japan (http://ipt.pensoft.net/resource.do?r=shellfishes_in_kyushu)”. According to the Red Data Book published by the Japanese Ministry of Environment in 2018, 3 species were determined as Critically endangered and Endangered, 6 species were determined as Vulnerable and 13 species were determined as Near Threatened. The proportions of individuals classified as Critically endangered and Endangered from the total number of individuals were extremely low, but the proportions of Near Threatened individuals were high. Our results indicate that the risk of molluscan extinction in small- and medium-sized river estuaries in Kyushu is high and that immediate conservation is necessary.

Evidence of sewage input to inner shelf sediments in the NE coast of Brazil obtained by molecular markers distribution

Coprostanol (5β-cholestan-3β-ol) and other fecal steroids were used as markers to trace the input of sewage to the shelf along the coast of Sergipe and Alagoas States, in NE Brazil. Surface sediment samples in shallow regions (<50m depth) on the shelf were collected adjacent to four fluvial systems, whose drainage basins exhibit distinct levels of human influence. Highest coprostanol concentrations were observed in the area under influence of the Sergipe River (58.6±74.6ngg−1; maximum of 184.1ngg−1), whereas in the Vaza-Barris (18.9±23.6ngg−1) and the Piaui/Real (12.3±6.7ngg−1) rivers the levels of coprostanol were near the method’s limit of detection. Nearby the São Francisco River, the largest in the NE Brazil, coprostanol was virtually absent. The findings of the present study, supported by coprostanol-based diagnostic ratios, revealed that, when sanitation is lacking in the coastal region, even a small-sized river like the Sergipe River can effectively contribute to the export of sewage-derived organic matter to the inner continental shelf in the studied region.

Spatio-temporal variation in the hydrochemistry of Tawa River, Central India: effect of natural and anthropogenic factors

Tawa River is the biggest left bank tributary of the Narmada, the largest west-flowing river of the Indian peninsula. Central India enjoys a tropical climate, is highly urbanized, and the river flow is mostly controlled by monsoon; a large part of the population depend on rivers for their livelihood. Spatial and temporal variations in the hydrochemistry of the Tawa River were studied based on seasonal sampling along the course of the river and its tributaries. The study is important because not much data exist on small size rivers and the river processes spell out correctly in smaller basins. The monsoon season accounts for more than 70% of river water flow. The basin is characterized by silicate lithology; however, water chemistry is controlled by carbonate-rich soils and other weathering products of the silicate rocks, as indicated by the high (Ca + Mg)/(Na + K) ratios (>3.8). The values of the Na-normalized ratios of Ca(2+), Mg(2+), and HCO₃(-) suggest that both the carbonate and silicate lithology contribute to the hydrochemistry. On average, 42% of HCO₃(-) in the Tawa River water is contributed by silicate weathering and 58% from carbonate lithology. The water remains undersaturated with respect to calcite during the monsoon and post-monsoon seasons and supersaturated during the pre-monsoon season. A significant influence of mining in the basin and other industrial units is observed in water chemical composition.

An Analytical Study on the Structural Performance Evaluation of the Multistage Overturing Movable Gate

Numerous water gates have been constructed and are under construction for the control of water level because, due to the topographical characteristics of mountainous area, many small size rivers are developed in Korean peninsula. Among the water gates, movable water gates are more efficient to control water level than the fixed water gates. By the field application of the movable water gates, many problems associated with the fixed water gates have been mitigated. The problems include the bottom water pollution, the change of habitats for the riparian organisms, etc. This is the reason to increase the field application of movable water gates. In the paper we present the result of analytical investigation pertaining to the structural behavior of multistage overturning movable water gate which is one of the movable water gates. In the analytical investigations, the finite element analysis on the constructed water gate has been conducted for illustration purposes and it was found that the multistage movable water gate is much better than the fixed and/or existing movable water gates in the point of structural and environmental performances.

Study on the Flood Volume Investigation for Medium and Small River

The hydrological research of ungauged basins became the new topic of international hydrological plan, the flood investigation can effectively make up for the information insufficient of the contemporary remote sensing technology and traditional statistical interpolation techniques. Take Dasha River rainstorm for example, water surface slope was monitored of 8‰ by slope-area method, the peak flow was calculated of 1830 m3/s. According to the measured multi-peak flood hydrograph simulates single peak hydrograph and five points probable, the flood volume was calculated of 109 million m3, the runoff coefficient is 0.84 and runoff depth is 505 mm. The river basin has 250 mm previous rainfall, and the underlying surface was saturated, so the result indicated that it accord with runoff yield and concentration theory. The method can be extended for medium and small size river.

Measurement of the flood discharge of a small-sized river using an existing digital video recording system

In this study, a closed-circuit television (CCTV) system, installed for surveillance purposes, is utilized to measure the flow rate during a flood. The procedure to determine both the angle and scale-factor of the camera is described. Then, image analysis techniques, namely the direct visual measurement method, Large-Scale PIV (LSPIV) and Space-Time Image Velocimetry (STIV), are applied to the video images recorded by the CCTV camera. The results of these methods and the conventional float measurement are compared. In addition, the accuracy of the respective methods is discussed. A set of low-quality video images of a flood during a thunderstorm that occurred under the dark ambient conditions (midnight) is analyzed using three image-based methods. The transition of the flow rate during the event is successfully estimated.

Distribution and fluxes of fluorescent whitening agents discharged from domestic wastewater into small rivers with seasonal changes of flow rates

Distributions of fluorescent whitening agents (FWAs) in the waters of a small river system in Japan were surveyed in summer when the water volume rose following high precipitation and in winter when it subsided as precipitation declined. The main source of FWAs in the river system was domestic wastewater, and fluxes in the tributaries depended on the size of the residential population and the elimination rates of sewage treatment systems in their catchments, although FWA concentrations in the river itself fluctuated, largely as a consequence of dilution by heavy precipitation and unstable water flows in the small-sized river system. The FWA concentrations in the river waterduring summer decreased not only by the dilution of river water but also by photodegradation because of more prolonged exposure to sunlight.

A one-dimensional model for water quality simulation in medium- and small-sized rivers

While studying water quality in the Tatara river, we realized that the river has various hydraulic and topographic characteristics when flowing through different regions. Because of these specific characteristics, the application of the existing models for simulation of its water quality may not be appropriate due to limitations in the models themselves. Therefore, we developed a mathematical model that is suitable for short-term simulations of water quality in rivers with characteristics similar to the Tatara river. The main foundation of the model is the one-dimensional transport equation established on the basis of the mass conservation law. To solve this equation numerically, it was discretized by the method of finite-difference approximations, and an algorithm has been programmed in Fortran 90. To verify the model, the Tatara river was chosen as a case study. Water temperature, dissolved oxygen, hydraulic parameters in four typical blocks of the river, and meteorological data of the study area, have been observed and used to test the model. By calibrating the model with different series of data collected from the designated blocks, all results have shown a good fit between simulated data and the observed one. Therefore, the model could be a reliable tool for simulating water quality in medium- and small-sized rivers over a short-term period. This research has also indicated the changing tendencies of water temperature and dissolved oxygen in Tatara river in response to different meteorological patterns over a daily 24-h period. Besides, the model could be improved to simulate other water quality variables, which would be studied further.

The response of zoobenthos to “natural channelization” of a small river

In October 2003, the small-sized river Gałęzówka (Lublin Upland) was channelized on its prevailing length, according to the assumptions of so-called “natural channelization”, i.e. among others, without straightening the river channel and leaving some river sections untouched. The surveys were carried out in 2003–2004, before and after the channel works, at two 100m long sections: the disturbed site, and one placed upstream untouched reference site.Physical and chemical analysis suggested slightly better water quality at the reference site. Both density and biomass of the zoobenthos at the two sites were predominated by chironomid larvae and Tubificidae. The channel works did influence strongly taxa richness, dominance structure, density and biomass of the fauna. This was evident especially one month after the channel works. Values of Shannon-Wiener diversity index were higher at the disturbed site, however. The seasonal changes in density and biomass at the disturbed site exhibited a different pattern than at reference one. After one month after the channel works, the fauna of the two sections studied exhibited rather high level of faunistic similarity, suggesting high rate of animal communities reviving.