River Environmental Management Research Articles

Quantifying Spatio-Temporal River Morphological Change and Its Consequences in the Vietnamese Mekong River Delta Using Remote Sensing and Geographical Information System Techniques

The evolution of delta and riverbank erosion within the river basin can significantly impact the environment, ecosystems, and lives of those residing along rivers. The Vietnamese Mekong Delta (VMD), counted among the world’s largest deltas, has undergone significant morphological alterations via natural processes and human activities. This research aims to examine these morphological alterations and their impacts on local economic and social conditions in the VMD. This study utilized satellite data from 1988 to 2020, coupled with population density and land use/land cover (LULC) maps from 2002, 2008, and 2015. The findings reveal that the VMD experienced widespread erosion over the past three decades, covering an area of 66.8 km2 and affecting 48% of the riverbank length (682 km). In contrast to riverbanks, islets showed an accretion trend with an additional area of 13.3 km2, resulting in a decrease in river width over the years. Riverbank and islet erosion has had a profound impact on the LULC, population, and economy of the provinces along the VMD. From 2002 to 2020, eight different land use types were affected, with agricultural land being the most severely eroded, constituting over 86% of the total lost land area (3235.47 ha). The consequences of land loss due to erosion affected 31,273 people and resulted in substantial economic damages estimated at VND 19,409.90 billion (USD 799.50 million) across nine provinces along the VMD. Notably, even though built-up land represented a relatively small portion of the affected area (6.58%), it accounted for the majority of the economic damage at 70.6% (USD 564.45 million). This study underscores the crucial role of satellite imagery and GIS in monitoring long-term morphological changes and assessing their primary impacts. Such analysis is essential for formulating effective plans and strategies for the sustainable management of river environments.

Dynamic real-time forecasting technique for reclaimed water volumes in urban river environmental management

In recent years, the utilization of wastewater recycling as an alternative water source has gained significant traction in addressing urban water shortages. Accurate prediction of wastewater quantity is paramount for effective urban river water resource management. There is an urgent need to develop advanced forecasting technologies to further enhance the accuracy and efficiency of water quantity predictions. Decomposition ensemble models have shown excellent predictive capabilities but are challenged by boundary effects when decomposing the original data sequence. To address this, a rolling forecast decomposition ensemble scheme was developed. It involves using a machine learning (ML) model for prediction and progressively integrating prediction outcomes into the original sequence using complementary ensemble empirical mode decomposition with adaptive noise (CEEMDAN). Long short-term memory (LSTM) is then applied for sub-signal prediction and ensemble. The ML-CEEMDAN-LSTM model was introduced for wastewater quantity prediction, compared with non-decomposed ML models, CEEMDAN-based LSTM models, and ML-CEEMDAN-based LSTM models. Three ML algorithms—linear regression (LR), gradient boosting regression (GBR), and LSTM—were examined, using real-time prediction data and historical monitoring data, with historical data selected using the decision tree method. The study used daily water volumes data from two reclaimed water plants, CH and WQ, in Beijing. The results indicate that (1) ML models varied in their selection of real-time factors, with LR performing best among ML models during testing; (2) the ML-CEEMDAN-LSTM model consistently outperformed ML models; (3) the ML-CEEMDAN-LSTM hybrid model performed better than the CEEMDAN-LSTM model across different seasons. This study offers a reliable and accurate approach for reclaimed water volumes forecasting, critical for effective water environment management.

Hydraulic Effect of Vegetation Zones in Open Channels: An Experimental Study of the Distribution of Turbulence

The development of vegetation in riverbeds is an important part of river engineering, and an in-depth understanding of its hydraulic influence is greatly needed. Our research focuses primarily on common reed (Phragmites australis) in riverbeds. To date, little is known about the hydraulic impact of the Phragmites australis reed and both field and laboratory data are still very scarce. Consequently, the main goal of our study was to evaluate the effect of vegetation zones on the spatial distribution of turbulence. Based on laboratory measurements of local instantaneous velocities, the values of the turbulence intensity (degree) Tu were determined, and its spatial distribution was illustrated. Analysis of the results showed that the relatively dense clusters of plants (reeds) act as “openwork deflectors” of the current and very clearly shape its spatial distribution. This can also be observed in the case of the distribution of the turbulence parameter Tu. For example, in the case of the development of riparian vegetation in the form of quasi-triangular communities of common reed (Phragmites australis) located alternately, there is a channelization of the flow, but also spatial changes in its character that occur. This work only presents results for preliminary hydraulic tests for Phragmites reed. These experiments should also be continued for other species of flexible riparian vegetation such as wicker. In the laboratory, the hydraulic influence of only triangle-shaped vegetation zones has been studied. Therefore, there is also a need for further hydraulic studies on vegetation zones of shapes other than triangular, e.g., rectangular, as well as vegetation zones with irregular shapes The authors see the need for such research and have already planned its continuation. Research on the interactions between vegetation and the structure of water flow in the riverbed is a very important aspect of contemporary trends in river environment management. Conscious, planned, and model-tested locating (or removing) of vegetation in a stream allows for shaping hydraulic and morphological conditions, thus controlling the processes of erosion, transport, and accumulation of debris.

Optimization of river environmental management based on reinforcement learning algorithm: a case study of the Yellow River in China.

Generating scientific management strategy contributes to the sustainable development of river ecological environment. In this study, a multi-objective coupled water and sediment regulation model aiming at minimizing sedimentation and inundation loss as well as maximizing ecological value in the lower Yellow River has been developed. A reinforcement Q-learning algorithm was used to obtain optimized strategies from the multi-objective of sediment reduction, flood control and ecological restoration under different hydrological years. The results showed that the simulated channel sedimentation is very close to the measured value, which proves the applicability of the developed model. Under dry, normal and wet hydrological year, the effects of various regulation strategies on silt reduction, flood control and ecological restoration were obviously different. The regulation scheme of discharge at 3700 m3/s was verified to be suitable for dry and wet year, and that of discharge at 2600 m3/s was more suitable for normal year. Increasing the spacing of the beach area was better in normal year and wet year. Our findings suggested optimized strategies to address environmental challenges of the lower Yellow River in different hydrological years. This paper provides a reliable reference for improving the management of the lower Yellow River.

Hamilton–Jacobi–Bellman–Isaacs equation for rational inattention in the long-run management of river environments under uncertainty

A new stochastic control model for the long-run environmental management of rivers is mathematically and numerically analyzed, focusing on a modern sediment replenishment problem with unique nonsmooth and nonlinear properties. Rational inattention as a novel adaptive strategy to collect information and intervene against the target system is modeled using Erlangization. The system dynamics containing the river discharge following a continuous-state branching with an immigration-type process and the controlled sediment storage dynamics lead to a nonsmooth and nonlocal infinitesimal generator. Modeling uncertainty, which is ubiquitous in certain applications, is considered in a robust control framework in which deviations between the benchmark and distorted models are penalized through relative entropy. The partial integro-differential Hamilton–Jacobi–Bellman–Isaacs (HJBI) equation as an optimality equation is derived, and its uniqueness, existence, and optimality are discussed. A monotone finite difference scheme guaranteeing the boundedness and uniqueness of numerical solutions is proposed to discretize the HJBI equation and is verified based on manufactured solutions. Model applications are also conducted with the parameter values identified from the available data and physical formulae. The computational results suggest that environmental management should be rationally inattentive in a state-dependent and adaptive manner.

HJB and Fokker-Planck equations for river environmental management based on stochastic impulse control with discrete and random observation

We formulate a new two-variable river environmental restoration problem based on jump stochastic differential equations (SDEs) governing the sediment storage and nuisance benthic algae population dynamics in a dam-downstream river. Controlling the dynamics is carried out through impulsive sediment replenishment with discrete and random observation/intervention to avoid sediment depletion and thick algae growth. We consider a cost-efficient management problem of the SDEs to achieve the objectives whose resolution reduces to solving a Hamilton-Jacobi-Bellman (HJB) equation. We also consider a Fokker-Planck (FP) equation governing the probability density function of the controlled dynamics. The HJB equation has a discontinuous solution, while the FP equation has a Dirac's delta along boundaries. We show that the value function, the optimized objective function, is governed by the HJB equation in the simplified case and further that a threshold-type control is optimal. We demonstrate that simple numerical schemes can handle these equations. Finally, we numerically analyze the optimal controls and the resulting probability density functions.

Impact of Partially Covered Vegetation on the Lateral Velocity Distribution of Open Channel Flow

The vegetation affects the flow process and water environment, thus drawing increasing attention to river environment management. Previous research is mainly focused on flow through vegetation in a channel with fully covered single-layer vegetation. However, in natural rivers, different heights’ vegetation often co-exists along one or two sides of a river. This paper experimentally studies how the flow velocity distribution is affected by the two different-layered vegetation allocated along two sides of an open-channel. The vegetation was simulated by dowels of two heights, 10 cm and 20 cm, and arranged in a parallel pattern along two sides of a flume under partially submerged conditions. The velocities along a cross-section were measured by Acoustic Doppler Velocimetry (ADV). The results of lateral velocity distribution show that a strong shear layer exists between vegetation and non-vegetation zones, indicating the retarding effect of vegetation. Meanwhile, as the flow depth increases, the relative velocity in the free flow zone decreases compared with that in the vegetated region, indicating that vegetation resistance to the flow decreases as increasing depth under the same vegetation configuration. These ?ndings would help understand the role of multi-layered vegetation in riparian management.

Long-term agricultural contamination shaped diversity response of sediment microbiome

The pollution caused by agricultural production poses a threat to the ecological integrity of river ecosystems, altering the structure and function of river ecosystems. Differences in microbial community structure provide useful information about the impact of agricultural pollution on the biological integrity of ecosystems, but generally convey little information regarding ecosystem functions. In this study, using Illumina MiSeq sequencing technology based on the 16S rRNA gene, river sediment samples associated with four different types of agricultural pollution were comprehensively analyzed. The results show that the total organic carbon (TOC) content was highest at the YZS site (animal husbandry sewage) among the assayed sites, but the species richness and uniformity were lowest at this site, which may have been caused by the high nutrient source of the sewage. Furthermore, in the three YZS samples affected by the long-term discharge of aquaculture tail-water, the unique genus Dechloromonas and the genus Candidatus-Competitor were observed, which are strongly correlated with phosphorus conversion. The formation of network modules may correspond to the coexistence of functional bacteria accustomed to multiple niche combinations under different agricultural pollution conditions in river sediments. According to the PICRUSt functional prediction, the bacterial community in the agricultural polluted river sediment primarily harbored 46 subfunctions, exhibiting richness of functions. Overall, our results provide a more comprehensive understanding of the structure and ecological processes associated with the aggregation of bacterial communities, which is beneficial for the management of river environments.

The Integrated Quality Analysis of Sediment on BanjirKanal Barat River as the Basis of River Environment Management

There have been many studies on the pollution status of Banjir Kanal Barat (BKB) River; however, many of them are limited to the concentration of metals in the river water and their biodiversity of water biota, and partial analysis. The study aims to analyse the metal concentration in BKB river sediment, its toxic to water biota and the effect on the abundance and diversity of macrozoobenthos. The evaluation of pollution status is conducted with three components integrated approach. The sediments were collected from three sampling stations with three replications. While the community observation included abundance, diversity, evenness and dominance of macrozoobenthos. Toxicity testing had been carried out to observe the inhibition of the growth of Chlorella sp algae in pore water sediments and failure reburial of blood clams into the substrate/sediment. While the evaluation of pollution status was conducted in an integrated three components approach. The results showed that the concentrations of various metals in the sediment were varied. The concentration of metals in sediments were still within natural limits and identical to the reference station that was not polluted. The types of macrozoobenthos were found about nine genera with varying in abundance, diversity index, evenness index, and dominance index. The abundance, diversity index, evenness index, dominance index of macrozoobenthos at all stations were still identical with reference stations, which known was not polluted. Although pore water sediments and sediments from various stations caused inhibition of the growth of Chlorella sp and the failure reburial of blood clams, statistically analysis was not significantly different from the reference station. Overall it can be stated that the sediment quality in those three stations was still excellent, however, they need to be maintained.

Mathematical Modeling for Decision-Making of Observation Timing and Workload for Cost-Effective River Environmental Management

Mathematical Modeling for Decision-Making of Observation Timing and Workload for Cost-Effective River Environmental Management

Monitoring and Assessment of Youshui River Water Quality in Youyang

By monitoring the water quality of Youshui River from January 2016 to December 2016, according to the indicator grading and the assessment standard of water quality, the formulas for 3 types water quality indexes are established. These 3 types water quality indexes, the single indicator index Ai, single moment index Ak and the comprehensive water quality index A, were used to quantitatively evaluate the quality of single indicator, the water quality and the change of water quality with time. The results show that, both total phosphorus and fecal coliform indicators exceeded the standard, while the other 16 indicators measured up to the standard. The water quality index of Youshui River is 0.93 and the grade of water quality comprehensive assessment is level 2, which indicated that the water quality of Youshui River is good, and there is room for further improvement. To this end, several protection measures for Youshui River environmental management and pollution treatment are proposed.

Application of synthetic iron-oxide coated zeolite for the pollution control of river sediments

Contaminants released from river sediments are catching more attentions for river environmental management, especially when external sources of river pollution have been well controlled. To reduce the contaminant release from sediments, in-situ capping is often applied because of its effective reduction of contaminant flux and minimal disturbance to the surroundings. As an innovative sediment capping material, iron-oxide coated zeolite (IOCZ) was synthesized, characterized, and evaluated in this study. Its performance for the NH4+-N, PO43−-P, and S2−-S fixation in aqueous solutions was evaluated using batch and fixed-bed column experiments. IOCZ was found effective as a sorbent for NH4+-N, PO43−-P, and S2−-S with the maximum Langmuir sorption capacities of 6.23 mg N g−1, 0.966 mg P g−1, and 1.70 mg S g−1, respectively. Under the studied conditions, the whole breakthrough process in the fixed-bed column could be well described by Thomas model, indicating IOCZ can effectively retard NH4+-N, PO43−-P, and S2−-S under flowing conditions. In addition, desorption simulative experiments suggested that the retarded pollutants were stable even under some extreme environments such as flooding or tiding. Therefore, IOCZ seems a promising capping material to control the release of NH4+-N, H2PO4−-P, and S2−-S from river sediments.

Integrated theory of river environmental management and flood control From nature friendly river management to Eco-DRR

Integrated theory of river environmental management and flood control From nature friendly river management to Eco-DRR

Impact of human activity and climate change on suspended sediment load: the upper Yellow River, China

Fluvial suspended sediment has multi-fold environmental implications and the study of the variation in suspended sediment load (SSL) of rivers is important both in environmental earth sciences and in river environmental management. Based on data collected for the upper Yellow River of China in the past 50–60 years, the purpose of this study is to elucidate the impact of human activity and climate change on SSL, thereby to provide some knowledge for the improvement of the drainage basin management. The results show that the SSL of the upper Yellow River exhibited a remarkable decreasing trend. A number of reservoirs trapped a considerable amount of sediment, resulting in a reduction in SSL at Toudaoguai station, the most downstream station of the upper Yellow River. The analyses based on Mann–Kendall’U and double-mass plot indicate some turning points, which were caused by the Liujiaxia and Longyangxia Reservoirs, two major reservoirs on the upper Yellow River. The implementation of soil and water conservation measures reduced the runoff coefficient, and therefore, the intensity of soil erosion. The climate change also played a role in reducing sediment yield. The increase in air temperature enhanced the evapo-transpiration and reduced the runoff, by which the SSL decreased. The decreased frequency of sand-dust storms reduced the amount of wind-blown, sand and dust to the river reaches located in desert, also reducing the SSL. Seven influencing variables are selected to describe the changing human activity and climate. As some of the influencing variables are strongly inter-correlated, the principle component regression was used to establish the relationship between SSL and the influencing variables. The squared multiple correlation coefficient is R 2 = 0.823. Some further research is suggested with the minerals and pollutants related with the SSL.

河川環境保全・再生のための地域活動に関する分析

It is important that residents do river environmental management,because reducing governmental burden, minization of the psuchological distance of residents and river and strengthening regional social network. Recently, these activities by cooperation of residents and administration are done.The purpose of this study makes clear the regional comparison and changing processes of the residential activities at the river.The year of starting activities increased in class A river. These activities increased from 1980s, and the most number of established party in 1988. As a result of analyzing the contents of actibities, it is shown that formation of a network which supports activity is important. An analysis of a possibility that activity will start was carried out. High potential river of environmental activity is elemntary school in the neighborhood, and much a afamily's number area.

京都鴨川における水辺環境評価の多基準評価システム構築に関する研究

Generally, evaluating the values of maintaining and preserving the environment is a difficult task. Multi-criteria analysis is expected as a new method for environmental evaluations to select the most desirable alternative by a weighting scheme in Europe. In river environment management, a method for evaluating natural factors as well as social factors influenced by the project is necessary. Establishing an evaluation method that reflects the opinions of residents around a river as well as the administration is also an urgent task. In this study, we assumed that when residents evaluate an alternative they do not use scientific information, but use their own impressions of the rivers. Based on this assumption, the multi-criteria evaluation model was used to establish a cognitive system to evaluate the impressions of the local residents. That is, the impression cognitive system was composed of Type 2 quantification methods for a questionnaire distributed around the Kamo River. Answers to questions about actions (ex, frequency to go to the river, etc.) were used as the dependent variables and nine impressions of the river were used as the explanatory variables. Finally, the possibility of consensus between upstream and downstream residents for river environment management of the Kamo River was examined with the established impression cognitive system.JEL Classification: Q51, R10, R53

A FRAMEWORK FOR THE SUCCESSFUL RIVER ENVIRONMENT MANAGEMENT MEASURES - VERIFICATION THROUGH CASE STUDIES IN JAPAN AND ABROAD -

The river environment management measures of today have been originated from some pioneering river works conducted to meet the request from the residents around 1970-1990 when the environmental issues were the serious social concerns. Establishing a framework for the successful river environment management measures will provide the useful indicators toward the adequate river management under the changeable socio-economic conditions of the future. This paper proposes the framework and verifies its adaptability to some pioneering river works in Japan and abroad. As a result, it was revealed that the directions of river environment management measures were influenced by the backgrounds of the times and the regional characteristics. And showing the purposes and the effects clearly was a good incentive to promote the river works. Especially, by establishing the partnership between the river authorities and the residents through close communication, the ownership of the rivers as the properties and symbols of the regions was fostered, which led to the continuous utilization of the rivers by the communities.

Re-connecting with a Recovering River through Imaginative Engagement

Imaginative engagement as a mode of citizen participation—the use of arts-based methods to involve people actively in shared learning experiences—holds promise as a means to increase awareness and understanding, and to build capacity, for sustainable use and management of rivers. We conducted a series of creative writing workshops in a former industrial area of northern England that were focused on a recovering river. Participants in the workshops found the process a positive experience and reported changes in their knowledge, attitudes, and actions about the use and management of river environments locally and more generally. The catchment consciousness of members appeared to increase, and their raised levels of interest led them to invest time in researching the history and geography of the river. We conclude that the method has significant potential for complementing collaborative approaches to river planning and management.

Effects of reducing river flow on pulse residence time in Little Manatee River, USA

Residence time is an important indicator for river environmental management. In this paper, a 3D hydrodynamic model has been successfully applied to Little Manatee River to characterize the mixing and transport process and residence time. The model employs horizontal curvilinear orthogonal grids to represent the complex river system that consists of branches and bayous. The model has been satisfactorily calibrated and verified by using two continuous data sets. The data sets consist of hourly observations of all forcing boundaries, including freshwater inputs, tides, winds, salinity and temperatures at bay boundary, and air temperatures for model simulations. The data sets also consist of hourly observations of water levels, salinity, and temperature at several river stations. The calibrated and verified hydrodynamic model was used to predict residence time in the Little Manatee River. Under the minimum flow of 0.312 m3/s, the pulse residence time (PRT) is 108 days. Model simulations were also conducted for 17 flow scenarios. Empirical regression equations have been satisfactorily derived to correlate PRT to freshwater inflow. Correlation coefficient R2 is 0.982 for PRT.

Transverse Mixing in a Trapezoidal Compound Open Channel

Transverse mixing characteristics of solute in the open channel flow can provide useful information for river environmental management. The lateral mixing coefficient is a crucial parameter for reproducing the transverse mixing either by numerical simulation or by analytical prediction. Since the solute mixing can be greatly affected by the lateral variations in water depth, mixing coefficient should be determined in each sub-section (i.e., the main channel, side slope and flood plain) separately. In this article, the transverse mixing in a symmetric trapezoidal compound channel was studied based on laboratory measurement of longitudinal and transverse velocity components and lateral distribution of solute concentration. The lateral mixing coefficient was estimated by adopting different Schmidt numbers in different sub-sections divided according to the developing trend of the eddy viscosity, and finally a piecewise linear profile of mixing coefficient was adopted to analytically predict the transverse solute concentration. The comparison between the analytically predicted data and the measuring solute concentration proved that this is an effective way to estimate the lateral mixing in the open channel flow with lateral variations in water depth.