scholarly journals Numerical Investigation on Infiltration and Runoff in Unsaturated Soils with Unsteady Rainfall Intensity

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 914 ◽  
Author(s):  
Jinqiang Tan ◽  
Hongqing Song ◽  
Hailong Zhang ◽  
Qinghui Zhu ◽  
Yi Xing ◽  
...  
Keyword(s):  
Unsaturated Soils ◽  
Flood Control ◽  
Rainfall Intensity ◽  
Flow Model ◽  
Theoretical Foundation ◽  
Urban Flood ◽  
Initial Stage ◽  
Cumulative Infiltration ◽  
Project Construction ◽  
Numerical Approaches

Modeling infiltration into soil and runoff quantitative evaluations is very significant for hydrological applications. In this paper, a flow model of unsaturated soils was established. A computational process of soil water content and runoff prediction was presented that combines an analytical solution with numerical approaches. The solutions have good agreements with the experimental results and other infiltration solutions (Richards numerical solution and classical Green–Ampt solution). We analyzed the effects on cumulative infiltration and runoff under three conditions of rainfall intensity with same average magnitude. These rainfall conditions were (Case 1) decreasing rainfall, (Case 2) steady rainfall, and (Case 3) increasing rainfall, respectively. The results show that the cumulative infiltration in Case 1 is the highest among the three cases. The cumulative runoff under condition of Case 3 is smaller than that of decreasing rainfall at the initial stage, which then becomes larger at the later stage. The time of runoff under the conditions of Case 1 is earliest among the three rainfall conditions, which is about 50% earlier than Case 3. Therefore, project construction for urban flood control should pay more attention to urban flood defense in increasing rainfall weather than other rainfall intensities under the same average magnitude. The approaches presented can be utilized to easily and effectively evaluate infiltration and runoff as a theoretical foundation.

scholarly journals Study on the Classification of Urban Waterlogging Rainstorms and Rainfall Thresholds in Cities Lacking Actual Data

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3328
Author(s):  
Bingyan Ma ◽  
Zening Wu ◽  
Huiliang Wang ◽  
Yuan Guo
Keyword(s):  
Return Period ◽  
Flood Control ◽  
Rainfall Intensity ◽  
Influencing Factor ◽  
Extreme Rainfall ◽  
Observation Data ◽  
Urban Flood ◽  
Storm Water Management Model ◽  
Different Characteristics

Extreme rainfall is the main influencing factor of urban waterlogging. Different types of rainfall often have different characteristics of waterlogging. In order to establish a more accurate urban flood control system, it is necessary to classify waterlogging rainstorms and divide their thresholds. This study proposes a method for applying web crawlers to identify waterlogging rainfall in cities lacking waterlogging observation data and classifying them using the rainfall intensity–duration curves. By selecting appropriate duration thresholds and return period, waterlogging rainstorms are divided into rainfall intensity waterlogging (IW), rainfall amount of waterlogging (AW), combined waterlogging (CW) and no waterlogging (NW). In the application of Zhengzhou City, China, the urban flood control standard and the rainfall time distribution characteristics are used as the basis for the selection of the return period and duration thresholds, and the storm water management model (SWMM) is constructed to simulate the 4 kinds of rainfall characteristics of waterlogging, which is similar to actual situations. It proves that the method is suitable for the classification and thresholds division of different waterlogging rainfall in cities. The results show that the best duration thresholds in Zhengzhou are 20 min (M20) and 60 min (M60), and the best return period standard is 2 a. The thresholds for the 4 types of waterlogging rainstorm are: M20 ≥ 26.47 mm, M60 ≥ 43.80 mm, CW; M20 ≥ 26.47 mm, M60 < 43.80 mm, IW; M20 < 26.47 mm, M60 ≥ 43.80 mm, AW; M20 < 26.47 mm and M60 < 43.80 mm, No waterlogging.

Sewer System for Improving Flood Control in Tokyo: A Step towards a Return Period of 70 Years

1994 ◽  
Vol 29 (1-2) ◽  
pp. 303-310 ◽  
Author(s):  
Kazuyuki Higuchi ◽  
Masahiro Maeda ◽  
Yasuyuki Shintani
Keyword(s):  
Return Period ◽  
Flood Control ◽  
Rainfall Intensity ◽  
Runoff Coefficient ◽  
Large Drop ◽  
Construction Costs ◽  
Sewer System ◽  
Construction Period ◽  
Metropolitan Government ◽  
Under Construction

The Tokyo Metropolitan Government has planned future flood control for a rainfall intensity of 100 mm/hr, which corresponds to a return period of 70 years, and a runoff coefficient of 0.8. Considering that the realization of this plan requires a long construction period and high construction costs, the decision was made to proceed by stages. In the first stage, the improvement of the facilities will be based on a rainfall intensity of 75 mm/hr (presently 50 mm/hr), corresponding to a return period of 17 years, and a runoff coefficient of 0.8. In the next stage the facilities will be improved to accommodate a rainfall intensity of 100 mm/hr. In the Nakano and Suginami regions, which suffer frequently from flooding, the plan of improvement based on a rainfall intensity of 75 mm/hr is being implemented before other areas. This facility will be used as a storage sewer for the time being. The Wada-Yayoi Trunk Sewer, as a project of this plan, will have a diameter of 8 m and a 50 m earth cover. This trunk sewer will be constructed considering several constraints. To resolve these problems, hydraulic experiments as well as an inventory study have been carried out. A large drop shaft for the trunk sewer is under construction.

Study on Urban Flood Control and Drainage in Beijing

2014 ◽  
Vol 1065-1069 ◽  
pp. 2381-2385
Author(s):  
Sen Guo Zhan ◽  
Bao Hui Men ◽  
Jia Jie Wu ◽  
Zheng Da Duan
Keyword(s):  
Heavy Rainfall ◽  
Flood Control ◽  
The Philippines ◽  
City Government ◽  
Urban Flood ◽  
The City ◽  
New Look

On 21 July 2012, a huge thunderstorm hit Beijing, prompting the city government to act immediately to deal with the emergency. Yet great losses were caused, exposing problems about urban flood control and drainage, and making people take a new look at them. It is not uncommon for a rainfall of such a degree to happen in Asia. Comparatively speaking, however, unlike in Beijing, fewer damages are caused in Taiwan, Japan and the Philippines given the same situation. In this article, therefore, the problems arising after a heavy rainfall and their solutions will be discussed.

Simulating transient infiltration in unsaturated soils

1998 ◽  
Vol 35 (6) ◽  
pp. 1093-1100 ◽  
Author(s):  
J R McDougall ◽  
I C Pyrah
Keyword(s):  
Hydraulic Conductivity ◽  
Unsaturated Soils ◽  
Flow Model ◽  
Unsaturated Flow ◽  
Surface Region ◽  
Infiltration Rate ◽  
Soil Suction ◽  
Wetting Front ◽  
Near Surface ◽  
Unsaturated Hydraulic Conductivity

Transient responses to various infiltration events have been examined using an unsaturated flow model. Numerical simulations reveal a range of infiltration patterns which can be related to the ratio of infiltration rate to unsaturated hydraulic conductivity. A high value of this ratio reflects a prevailing hydraulic conductivity which cannot readily redistribute the newly infiltrated moisture. Moisture accumulates in the near-surface region before advancing down through the soil as a distinct wetting front. In contrast, low values of the ratio of rainfall to unsaturated hydraulic conductivity show minimal moisture accumulation, as the relatively small volumes of infiltrating moisture are readily redistributed through the soil profile.Key words: numerical modelling, infiltration, unsaturated soil, soil suction, groundwater.

scholarly journals Community Satisfaction of the Urban Flood Control System Improvement Project (UFCSI)

2019 ◽  
Vol 1 (1) ◽  
pp. 29-34
Author(s):  
Mohammad Sofyan
Keyword(s):  
Community Involvement ◽  
Flood Control ◽  
City Government ◽  
Public Works ◽  
Project Implementation ◽  
Community Satisfaction ◽  
Urban Flood ◽  
Improvement Project ◽  
Land Clearing ◽  
The City

The purpose of this study is to encourage ownership, responsibility and to develop stakeholders and policy makers for the river normalization program in the pre-construction, construction and post-construction stages. The use of the IPA method to measure community satisfaction in the quadrants on the Importance Performance Matrix map. The results of the study showed that the socialization from the Department of Water and Public Works, when the project was finished, was not in line with community expectations. Flood control projects that have been built, coordination with the contractor at the time of project implementation, socialization from the city government prior to project implementation, socialization from the city government when the project is finished, socialization from the river hall at the time before project implementation, socialization from the river hall at the time the project was completed, dissemination of information from the irrigation service prior to project implementation, and community involvement in project implementation. The process of land clearing, and the price agreement that has been reached. Improved land clearing, and price agreements that have been reached can be reconsidered because their impact on the benefits felt by the community is very small.

scholarly journals Modelling free gas overpressure in peat layers

2020 ◽  
Vol 195 ◽  
pp. 02027
Author(s):  
Stefano Muraro ◽  
Cristina Jommi
Keyword(s):  
Unsaturated Soils ◽  
Barometric Pressure ◽  
Pressure Oscillations ◽  
Global Response ◽  
Free Gas ◽  
Soil Skeleton ◽  
Changes Over Time ◽  
Fully Coupled ◽  
Over Time ◽  
Numerical Approaches

The paper assesses fully coupled hydro-mechanical numerical approaches developed for unsaturated soils to model the effect of free gas overpressure on the response of peat layers. A simple linear model is used for the soil skeleton, however, the global response is non-linear due to changes over time of the compressibility of the solid skeleton over the compressibility of the fluid, and solubility of gas in water. The overpressure generated in foundation peat layers by barometric pressure oscillations is modelled, and the results are compared to literature data. The development of pore overpressure upon unloading is analysed as a function of the soil skeleton compressibility, and the consequences on the average stress acting on the soil skeleton are discussed.

scholarly journals Estimating urban flood risk – uncertainty in design criteria

2015 ◽  
Vol 370 ◽  
pp. 3-7 ◽  
Author(s):  
M. Newby ◽  
S. W. Franks ◽  
C. J. White
Keyword(s):  
Data Analysis ◽  
Flood Risk ◽  
Rainfall Intensity ◽  
Design Criteria ◽  
Climate Change Scenarios ◽  
Urban Flood ◽  
Frequency Distributions ◽  
Rainfall Variation ◽  
Design Rainfall ◽  
Australian Rainfall

Abstract. The design of urban stormwater infrastructure is generally performed assuming that climate is static. For engineering practitioners, stormwater infrastructure is designed using a peak flow method, such as the Rational Method as outlined in the Australian Rainfall and Runoff (AR&amp;R) guidelines and estimates of design rainfall intensities. Changes to Australian rainfall intensity design criteria have been made through updated releases of the AR&amp;R77, AR&amp;R87 and the recent 2013 AR&amp;R Intensity Frequency Distributions (IFDs). The primary focus of this study is to compare the three IFD sets from 51 locations Australia wide. Since the release of the AR&amp;R77 IFDs, the duration and number of locations for rainfall data has increased and techniques for data analysis have changed. Updated terminology coinciding with the 2013 IFD release has also resulted in a practical change to the design rainfall. For example, infrastructure that is designed for a 1 : 5 year ARI correlates with an 18.13% AEP, however for practical purposes, hydraulic guidelines have been updated with the more intuitive 20% AEP. The evaluation of design rainfall variation across Australia has indicated that the changes are dependent upon location, recurrence interval and rainfall duration. The changes to design rainfall IFDs are due to the application of differing data analysis techniques, the length and number of data sets and the change in terminology from ARI to AEP. Such changes mean that developed infrastructure has been designed to a range of different design criteria indicating the likely inadequacy of earlier developments to the current estimates of flood risk. In many cases, the under-design of infrastructure is greater than the expected impact of increased rainfall intensity under climate change scenarios.

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