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The problem of a rising shallow water-table level in the coastal city of Dammam in eastern Saudi Arabia was investigated through data collection, analysis, and numerical modelling. The research focused on applying a coupled model that considers flow in both the saturated and unsaturated zones. Geophysical and hydrogeological data were collected thr...
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... simulation results were evaluated against the measured values using the statistical measures presented in Eqs. (17), (18) and (19), as shown in Table 3. The statistical measures are given for each month as an average of the values obtained at the considered locations of the study area. ...
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Citations
... The magnitude and intensity of these natural disasters range over time and space (Tsakiris 2014). The intensity and frequency of flood events have increased during the last few decades as a result of global climate change and human activities (Mokhtar et al. 2018); in addition, flooding has been found to be caused by shallow groundwater rise (Iwalewa et al. 2016). Over the last three decades, the destructive flood events happened in the world and led to the loss of thousands of lives, destruction of economic infrastructure and public properties, and significantly affected historical monuments. ...
Annual fluvial and pluvial floods happened in Lower Ping River Basin, Thailand. A flood hazard assessment approach was performed in the present study to evaluate flood impacts. The coupled 1D-2D hydrodynamic (HD) modeling package was applied for different return periods to investigate and classify the flood hazards. The 1D hydrodynamic model was calibrated for flood year 2011 at discharge and water level stations. The 2D hydrodynamic model was calibrated using observed flood map. Flood hazards were categorized based on critical flood depths for flooding scenarios of 2-, 5-, 10-, 25-, 50-, and 100-year return periods. The results showed that 28.8% of the total basin area (2423.8 km 2) was flooded during the 100-year return period, and the maximum flood inundation area was observed in Kamphaengphet and Nakhon Sawan provinces. Mostly, the flooded area under each return period was categorized under high hazard, followed by low and medium, and the least area was classified under a very high hazard level. More than 40% of sub-districts' area of Kamphaengphet and Nakhon Sawan provinces were flooded, which is located along the Ping River, while less than 20% sub-districts' area was flooded in Tak Province. The government and local stakeholders need to consider structural and nonstructural measures to reduce flood impacts in three provinces, and priority-based areal flood management approaches should be considered during the implementation of flood mitigation measures.
... That model was not coupled to a pipe flow model. Iwalewa et al. [2016] used a numerical model to investigate GW level rise driven by pipe water exfiltration in a case study in Dammam city, Saudi Arabia. That model takes saturated-unsaturated flow into account and consists of a coupled MODFLOW [Harbaugh et al., 2000]-HYDRUS [Simunek et al., 2005] procedure. ...
Pipe leakage related to defect urban sewer and stormwater pipe networks may lead to
subsurface contamination, reduction of groundwater recharge or a significant decrease of
the groundwater table. The quantification of pipe leakage is challenging, mostly due to the
uncertain forming of a colmation layer in the defect vicinity and inaccessibility of both,
pipe defects and the surrounding soil. Numerical models can be used to quantify leakage.
At present times, only few physically-based pipe leakage models exist, all of which either
neglect or simplify variably-saturated flow.
In the present dissertation, a novel and unique three-dimensional physically-based pipe
leakage model for variably saturated soil is presented. The model consists of the newly
implemented coupling between the pipe flow simulator HYSTEM-EXTRAN and the
unsaturated-saturated flow simulator OpenGeoSys. The coupling is based on updating
of boundary conditions and source terms. The interprocess data transfer is realized using
a shared-memory. The pipe leakage model is successfully validated and verified using a
newly generated benchmark library for pipe leakage models. Benchmarks are based on two physical experiments described in literature and two newly derived analytical solutions.
A novel method for upscaling pipe leakage is presented. The method enables to significantly reduce the local refinement of spatial discretization in the pipe vicinity, which
leads to a substantial reduction of computational costs. The method is based on leakage
functions. Two leakage functions representing both, sewer and stormwater pipe leakage
are presented. Accuracy and time efficiency of the upscaling method is demonstrated by
comparing results from a fully discretized model and an upscaled model.
In the present dissertation, the pipe leakage model is applied to several case studies to
investigate the pipe leakage process. Model setups represent (i) a single defect, (ii) a leaky sewer pipe of 30 m length, and (iii) a 53 km long defect stormwater pipe network in an urban catchment.
Results of the single defect and leaky sewer pipe model (models i,ii) show that leaky pipes can hydraulically disconnect from groundwater. It is found that, for a given pipe water level, pipe water exfiltration converges as the groundwater table is lowered. Further, it is found that pipe water exfiltration increases as the intensity and duration of pipe flow events increase. The temporal distribution of pipe flow has a negligible effect on pipe
water exfiltration.
Results of the model representing a defect stormwater pipe network in an urban catchment (model iii) show the impact of pipe leakage on urban groundwater. It is shown that groundwater infiltration into a largely defect pipe network may be in the order of annual groundwater recharge. Further, it is shown that groundwater infiltration may reduce the groundwater table by several meters and that the groundwater table may be lowered to the elevation of the pipe network.
... The existing master plans used for land development of urban areas fail to match unpredictable manifestations like flooding (Hsu et al. 2014). Road expansion and urban development could increase the risk of flood occurrence (Iwalewa et al. 2016). Although the flood avoidance is impossible and inevitable, future floods can be delineated through employing forecasting techniques (Tehrany et al. 2015). ...
This paper investigates the application of logistic regression model for flood susceptibility mapping in southern Gaza Strip areas. At first, flood inventory maps were identified using Palestinian Water Authorities data and extensive field surveys. A total of 140 flood locations were identified, of which 70% were randomly used for data training and the remaining 30% were used for data validation. In this investigation, six causing flood variables from the spatial database were prepared, which are digital elevation model (DEM), topographic slope, flow accumulation, rainfall, land use/land cover (LULC), and soil type. Then, comprehensive statistical analysis techniques including Pearson’s correlation, multicollinearity, and heteroscedasticity analyses were used, to ensure that the regression assumptions are not violated. The uniqueness of the current study is its inclusiveness of influential causing flood parameters and vigorous statistical analyses that led to accurate flood prediction. Quantitatively, the proposed model is robust with very reasonable accuracy. The prediction and success rates are 76 and 81%, respectively. The practical and unique contribution of this investigation is the generation of flood susceptibility map for the region. This is a very useful tool for
the decision makers in the Gaza Strip to reduce human harm and infrastructure losses.
The present study findings indicated that the sedimentation problem is severe. The most obvious impact of sedimentation in a reservoir is the cumulative loss of its storage capacity, affecting both the operational plan and economic investments based on reservoir use, especially in the drinking sector. To determine the most appropriate method for estimating suspended sediment in the Kardeh Dam reservoir located in a semi-arid region, measured flow discharge and suspended sediment load data at two hydrometric stations (Kardeh and Koshakabad) were investigated. To select an optimal model (with the best adaptation to hydrography operation results), the amount of suspended sediment transport by applying 6 models based on sediment rating curve equations and 14 individual and compound error criterias were estimated. By combining error criterias, 6 methods and 8 sub-methods were examined. It was found that the use of numerous individual or compound error criterias approximately has the same results, but using mean scores of individual/compound error criterias or only compound error criterias can improve the results. According to the results of statistics and hydrographic operations, a model of sediment rating curve equation is determined as the optimal model (model F). In this model, sediment discharge data can be divided into four categories according to hydrological conditions, and for each category, the equation of sediment rating curve was determined. It is suggested to conduct similar research in different climatic areas in order to investigate the effects of climatic conditions on data classification and selection of the most suitable sediment transport estimation model.
