scholarly journals The Influence of River Channel Occupation on Urban Inundation and Sedimentation Induced by Floodwater in Mountainous Areas: A Case Study in the Loess Plateau, China

2019 ◽  
Vol 11 (3) ◽  
pp. 761
Author(s):  
Zhihui Wang ◽  
Wenyi Yao ◽  
Ming Wang ◽  
Peiqing Xiao ◽  
Jishan Yang ◽  
...  
Keyword(s):  
Water Level ◽  
Loess Plateau ◽  
Flood Control ◽  
Control Strategies ◽  
River Channel ◽  
Mitigation Measures ◽  
River Channels ◽  
Mountainous Areas ◽  
The Loess Plateau ◽  
Urban Flood

River channel occupation has made cities in the mountainous areas more vulnerable to floodwater out of river channels during rapid global urbanization. A better understanding of the influence of river channel occupation on urban flood disasters can serve as a reference in planning effective urban flood control strategies. In this study, taking a flood event that occurred on July 26th, 2017 in a city on the Loess Plateau as an example, field surveys, dynamics detection of the river channel using remote sensing technology, and scenario simulations with a two-dimensional flow and sediment model were utilized to quantitatively analyze the impacts of river channel occupation on urban inundation and sedimentation. The results show that river channel dynamics reduced by construction can be successfully detected using the combination of high-resolution images and Landsat time-series images. The variation of the water level–discharge relationship caused by the narrowing of the river channel and the increase of the flood-water level caused by water-blocking bridges/houses result in a significant reduction of the flood discharge capacity. The contribution of the narrowing of the river channel was 72.3% for the total area inundated by floodwater, whereas 57.2% of urban sedimentation was caused by the construction of bridges/houses within the river channel. Sustainable flood mitigation measures were also recommended according to the investigations and research findings in this study in order to reduce the social, environmental and economic damages caused by floods.

Study of Urban Flood Control Planning in Taiyuan

2013 ◽  
Vol 838-841 ◽  
pp. 1709-1714
Author(s):  
Xiu Yong Yi ◽  
Yang Zhang
Keyword(s):  
Soil Conservation ◽  
Flood Control ◽  
River System ◽  
Control Measures ◽  
River Channels ◽  
Mountainous Areas ◽  
Urban Flood ◽  
Existing Problems ◽  
Downstream Area ◽  
Soil Conservation Measures

Considering topography, climate, river system, and existing problems in Taiyuan, the urban flood control planning in Taiyuan boils down to the following points: determine the flood control standard according to the size of city; study the flood alleviating measures in the upstream area; provide adequate water and soil conservation measures in the mountainous areas reduce flash floods; divert flood from mountainous areas to the downstream area instead of to the urban; improve the river channels in the urban area; provide flood detention and retarding area in the downstream area; study non-engineering flood control measures.

scholarly journals Changes in stage–flow relation of the East River, the Pearl River basin: causes and implications

2012 ◽  
Vol 44 (4) ◽  
pp. 737-746 ◽  
Author(s):  
Qiang Zhang ◽  
Kun Li ◽  
Vijay P. Singh ◽  
Xiaohong Chen ◽  
Jianfeng Li
Keyword(s):  
Water Level ◽  
River Basin ◽  
Flood Control ◽  
Morphological Changes ◽  
River Channel ◽  
Pearl River Basin ◽  
Abrupt Decrease ◽  
East River ◽  
The Pearl River ◽  
High Level

Water level and streamflow extracted from 891 hydrological episodes from both dry and flood seasons covering a period of 1954–2009 were analyzed to investigate stage–flow relations. Results indicate the following. (1) Since the early 1990s the low/high flow is increasing/decreasing. The water level, particularly the high level, is consistently decreasing. An abrupt decrease of water level is observed since the early 1990s at the lower East River. (2) Stage–streamflow relation is usually stable in the river reach with no significant bedform morphological changes. Changes in the geometric shape of the river channel are the major cause of the change in the stage–streamflow relation. (3) An abrupt decrease of water level at the Boluo station is mainly the result of abnormally rapid downcutting of the riverbed due to extensive sand dredging within the channel which caused serious headwater erosion. This human-induced modification by downcutting of the river channel may lead to significant hydrological alterations and may have critical implications for flood control, conservation of eco-environment, and also for basin-wide water resources management in the lower East River basin.

scholarly journals Improved Runoff Simulations for a Highly Varying Soil Depth and Complex Terrain Watershed in the Loess Plateau with the Community Land Model

2021 ◽  
Author(s):  
Jiming Jin ◽  
Lei Wang ◽  
Jie Yang ◽  
Bingcheng Si ◽  
Guo-Yue Niu
Keyword(s):  
Loess Plateau ◽  
Complex Terrain ◽  
Soil Depth ◽  
Loess Soil ◽  
Soil Evaporation ◽  
Hydrological Processes ◽  
River Channels ◽  
The Loess Plateau ◽  
Deep Soil ◽  
Community Land Model

Abstract. This study aimed to improve runoff simulations and explore deep soil hydrological processes for a watershed in the center of the Loess Plateau (LP), China. This watershed, the Wuding River Basin (WRB), has very complex topography, with soil depths ranging from 0 to 197 m. The hydrological model used for our simulations was the Community Land Model (CLM) version 5 developed by the National Center for Atmospheric Research. Actual soil depths and river channels were incorporated into CLM to realistically represent the physical features of the WRB. Through sensitivity tests, CLM with 150 soil layers produced the most reasonable results and was adopted for this study. Our results showed that CLM with actual soil depths significantly suppressed unrealistic variations of the simulated sub-surface runoff when compared to the default simulations with a fixed soil depth of 8 m. In addition, CLM with higher-resolution soil layering slightly improved runoff simulations, but generated simulations with much smoother vertical water flows that were consistent with the uniform distribution of soil textures in our study watershed. The runoff simulations were further improved by the addition of river channels to CLM, where the seasonal variability of the simulated runoff was reasonably captured. Moreover, the magnitude of the simulated runoff remarkably decreased with increased soil evaporation by lowering the soil water content threshold, which triggers surface resistance. The lowered threshold was consistent with the loess soil, which has a high sand component. Such soils often generate stronger soil evaporation than soils dominated by clay. Finally, with the above changes in CLM, the simulated total runoff matched very closely with observations. When compared with those for the default runoff simulations, the correlation coefficient, root-mean-square error, and Nash Sutcliffe coefficient for the improved simulations changed dramatically from 0.02, 10.37 mm, and −12.34 to 0.62, 1.8 mm, and 0.61. The results in this study provide strong physical insight for further investigation of hydrological processes in complex terrain with deep soils.

scholarly journals A Method for Dynamical Sub-Watershed Delimitating by No-Fill Digital Elevation Model and Defined Precipitation: A Case Study of Wuhan, China

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 486
Author(s):  
Hongping Zhang ◽  
Xinwen Cheng ◽  
Lei Jin ◽  
Dong Zhao ◽  
Tianjing Feng ◽  
...  
Keyword(s):  
Water Level ◽  
Digital Elevation Model ◽  
Flood Control ◽  
Return Periods ◽  
Wuhan City ◽  
Urban Flood ◽  
Digital Elevation ◽  
Elevation Model ◽  
Control Management

Watershed delimitation is very important in flood control management. The traditional sub-watersheds delimitated by a filling digital elevation model (DEM) may change the real sink area, such that it may not be the best choice in studies sensitive to sub-watershed storage. This paper proposes a dynamical watershed delimitation method using a no-fill DEM and precipitation. It considers a closed sink area containing cells that fully flow into a large special cell, which can flow out when its water level is “higher than outlet”. We took Wuhan City as a study area and defined the precipitation in return periods of 1, 5, 20, or 100 years to derive the sub-watersheds. It is found that, in the four delimitations, the ratio of isolated basic units which could not flow outside were 27%, 9%, 5%, and 1%, respectively, as the precipitation increased. The results show that the provided method satisfies the assumption that the sink area might overflow with increased precipitation. The sub-watershed delimitated by the proposed method has higher correlation with the distribution of waterlogging points than those delimitated according to the D8 algorithm. These findings indicate that the proposed method can derive reasonable sub-watershed delimitation and that it may be helpful in the practice of urban flood control management.

Analysis and Prediction for Xiaolangdi Reservoir Sand Blocking Operation Period and Water Level of the Lower Yellow River

2011 ◽  
Vol 71-78 ◽  
pp. 1318-1323 ◽  
Author(s):  
Qing An Li ◽  
Han Dong Liu ◽  
Yu Kun Zhao
Keyword(s):  
Water Level ◽  
Flood Control ◽  
Yellow River ◽  
River Channel ◽  
The Yellow River ◽  
Deposition Condition ◽  
Reservoir Water ◽  
Specific Flow ◽  
Operation Period ◽  
Xiaolangdi Reservoir

Xiaolangdi Reservoir undertakes 90% of the Yellow River runoff and 100% of sediment discharge. To ensure the long-term utilization of Xiaolangdi reservoir is the key to prevent the flood in the lower reaches of the Yellow River. Take Luokou Hydrologic Station located in the lower reaches of the Yellow River as an example, conduct an analysis from the aspects of sediment retaining of Xiaolangdi Reservoir, scouring and deposition condition of river channel in the lower reaches of the Yellow River, water level performance for years of different flow of ten times’ water-sediment regulation, predict on the sand blocking operation period of Xiaolangdi Reservoir, water level of specific flow of river channel in the lower reaches of the Yellow River and scouring and deposition condition of river channel, which has played a reference role for the flood control in the lower reaches of the Yellow River.

scholarly journals Evaluation of Real-Time Water Level Prediction Technology Using Statistical Models for Reducing Urban Flood Risk

2021 ◽  
Vol 16 (3) ◽  
pp. 387-394
Author(s):  
Mitsuhiro Nakashima ◽  
Shoichi Sameshima ◽  
Yuki Kimura ◽  
Midori Yoshimoto ◽  
◽  
...  
Keyword(s):  
Statistical Model ◽  
Water Level ◽  
Real Time ◽  
Flood Control ◽  
Prediction Models ◽  
Prediction Method ◽  
Observation Data ◽  
Urban Flood ◽  
Inland Flooding ◽  
Water Level Prediction

The frequency of localized short-term torrential rains that exceed the planned rainfall is increasing along with inundation damage due to inland flooding. Stepwise inundation measures utilizing existing stock and disaster prevention/mitigation for excessive rainfall are required. In this study, we describe the results of empirical research using a statistical model constructed based on rainfall and water level observation data as a highly accurate water level prediction method suitable for real-time prediction. This is aimed at application in flood control activities and operation support of pump facilities. By comparing and verifying the prediction accuracy between the water level prediction model and the statistical model by Convolutional Neural Network (CNN), which is generally used as an image recognition technology, the usefulness of the statistical model was confirmed. Further improvement in accuracy and widespread use of these water level prediction models are expected.

scholarly journals Assessing Hydrological Connectivity Mitigated by Reservoirs, Vegetation Cover, and Climate in Yan River Watershed on the Loess Plateau, China: The Network Approach

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1742
Author(s):  
Liang Zhao ◽  
Yu Liu ◽  
Yong Luo
Keyword(s):  
Land Cover ◽  
Loess Plateau ◽  
Vegetation Cover ◽  
Aridity Index ◽  
River Networks ◽  
Hydrological Connectivity ◽  
River Channels ◽  
The Loess Plateau ◽  
Wetness Index ◽  
River Watershed

Hydrologic connectivity is related to the water-mediated transport of matter, energy, and organisms within or between elements of the hydrologic cycle. It reflects the hydrological consequences caused by topographic, land cover, and climatic factors, and is an important tool to characterize and predict the hydrological responses to climate and landscape change. In the Loess Plateau region, a large number of reservoirs have been constructed to trap sediment and storage water for drinking, irrigation, and industries. The land cover has been significantly reshaped in the past decades. These changes may alter the watershed hydrological connectivity. In this study, we mapped the spatial pattern of hydrological connectivity with consideration of reservoir impedances, mitigation of climate, and land cover in the Yan River watershed on the Loess Plateau by using the network index (NI) approach that is based on topographical wetness index. Three wetness indices were used, i.e., topographical wetness index (TWI), SAGA (System for Automated Geoscientific Analyses) wetness index (WIS), and wetness index adopted aridity index (AI) determined by precipitation and evapotranspiration (WIPE). In addition, the effective catchment area (ECA) was also employed to reveal the connectivity of reservoirs and river networks to water source areas. Results show that ECA of reservoirs and rivers account for 35% and 65%, respectively; the hydrological connectivity to the reservoir was lower than that to the river networks. The normalized hydrological connectivity revealed that the connectivity to river channels maintained the same distribution pattern but with a decreased range after construction of reservoirs. As revealed by comparing the spatial patterns of hydrological connectivity quantified by NI based on WIS and WIPE respectively, vegetation cover patterns had significantly alternated watershed hydrological connectivity. These results imply a decreased volume of flow in river channels after reservoir construction, but with same temporal period of flow dynamic. It is illustrated that the network index (NI) is suitable to quantify the hydrological connectivity and it is dynamic in the context of human intervention and climate change.

scholarly journals Estimasi Model Hidrolika Menggunakan HEC-RAS 1-D dan Tren Prediksi Strategi Mitigasi Banjir

2022 ◽  
Vol 10 (1) ◽  
pp. 39-48
Author(s):  
Rian Mantasa Salve Prastica ◽  
Asvira Ditya Siswanto
Keyword(s):  
Water Level ◽  
Flood Control ◽  
Control Strategies ◽  
Flood Mitigation ◽  
Value Engineering ◽  
Field Observations ◽  
Construction Costs ◽  
Engineering Modeling ◽  
D Model ◽  
Level Profile

Engineering modeling is becoming a trend and important because it can simulate a variety of decision scenarios to be applied in the field. With limited facilities and technology, 1-D modeling in hydraulics for flood mitigation is still a trend today. What are the weaknesses of this model and how is the prediction of future modeling trends? This study analyzes the flood modeling of the Tuntang River with the 1-D model using HEC-RAS to analyze the condition of the existing water level profile and flood mitigation scenarios with normalization. The results of the analysis show that the 1-D model can describe conditions in the field and scenarios clearly. However, the 1-D model has limitations because it cannot carry out simulations that consider aspects of construction costs, time, and budget allocation of stakeholders to determine the priority scale of disaster-affected areas. It requires a vulnerability analysis with field observations, 2-D or 3-D modeling, and the application of value engineering to optimize flood control strategies. With the advancement of technology, this trend is predicted to be something that will be done in the future.

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