Journal of Hydrologic Engineering

Coastal regions have the most challenging aquifer systems because of their geometry and the flow behavior of groundwater with tidal oscillations. Studies have focused on tide-induced groundwater fluctuations in horizontal aquifers whose base is extending under the sea by ignoring the fact that coastal beaches are sloping in nature. In this study, an unconfined coastal aquifer with an extending, sloping, impermeable base under the sea in the presence of tidal waves and exponential rainfall infiltration was modeled. An analytical solution of the given hydrodynamic model with boundary conditions was developed, which represents the similarity of water table heights at two points in the given spatial domain. Nonlinear Boussinesq equations were linearized to develop the model. The closed form of the analytical solution was obtained using various transform methods. The efficiency of the linearization method was determined using the alternating direction implicit scheme. Relative percentage difference was used to analyze the error statistics between analytical and numerical results. Further, temporal and spatial distributions of the water table were presented for different bed slopes, tidal patterns, and rainfall infiltrations. The derived solution provided the responses of the coastal aquifer with a sloping base extending under the sea to tidal oscillations in the presence of rainfall infiltration. The developed model is useful for field and experimental applications of coastal aquifer systems such as seawater intrusion studies and water clogging on the coastal interface owing to the deposition of silt, clay, and pollutant particles.

Human interventions and climate change have caused significant alterations in the hydrologic response of several highly managed basins in Iran. One of these alterations is a considerable reduction in streamflow quantity, resulting in severe water supply insecurity. This paper presents an integrated modeling approach combining remote sensing, water balance analysis, reservoir operations, and water allocation policy evaluations. The approach helps in understanding of the relative contribution of anthropogenic factors in places where a major challenge is the lack of measured data for the historical time series of water withdrawals for agricultural development and water lost from the system through actual evapotranspiration (AET). Calibrated moderate-resolution imaging spectroradiometer (MODIS) remote sensing data of monthly AET (MOD16), modified Thornthwaite-Mather (M-TWM) water balance model, annual MODIS Land Cover Type (MCD12Q1) products (MCQD12Q1), mass curve analyses, and periodic analysis of water balance parameters were used to evaluate the contribution of anthropogenic factors and the effect of climatic impacts on the inflow time series for the Talvar Reservoir. The procedure led to an estimation of the naturalized series of the streamflow free of anthropogenic impacts; based on this, more plausible estimates of the basin’s future water availability were determined, which were then used in a water evaluation and planning (WEAP) model for Talvar Reservoir operations and water allocations. The study yielded four main results. First, it was seen that there were two abrupt change points in the analyzed mass curves, in the years 1998 and 2007, dividing the study period (1988–2012) into three periods. Periodic analysis of water balance parameters showed that while climate change caused streamflow changes in postimpact period A (1998–2007), intensified human activities brought about streamflow changes in postimpact period B (2008–2012). Secondly, it was found that the naturalized series of the Talvar streamflow had a better correlation coefficient with precipitation than the observed series for river flow. Thirdly, despite the proposed approach lacking the use of some water balance components such as soil moisture and snow water equivalent, the percentage of unaccounted water content was between 5% and 10%, indicating good accuracy of the proposed approach as a tool for sustainable water resources management. Fourth, the WEAP model simulation results demonstrated that the unfavorable condition of the aquifer can be ameliorated by applying proper management policies. The results also showed that to increase water supply security and facilitate sustainability, a certain amount of reduction in ground-water withdrawals and agricultural areas is inevitable.

Residential areas are major areas of runoff during urban floods, and many low-impact development (LID) measures have been developed to alleviate runoff at the source. In this paper, our goal is to provide a refined modeling method to simulate the entire physical rainfall–runoff process and thereby help communities visualize the actual runoff routing and quantify runoff timing and peak magnitude. The method employs a two-dimensional (2D) hydrodynamic numerical model and considers the discharge process of downspouts and overflow ports based on a high-resolution digital elevation model (DEM). Three test cases are used to compare the characteristics of the refined simulation method with those of a general modeling method that ignores the impacts of downspouts and overflow ports on runoff. The results reveal that the refined simulation method is able to reflect the actual runoff process. Thus, the refined simulation method can be used to accurately quantify the impacts of LID measures on runoff and aid urban planning and placement in residential areas.

This paper presents novel spatial analysis techniques to evaluate simulations of urban flood inundation from two hydrologic models applied using nationally available datasets. These techniques account for differences in model computational element size and discretization when comparing simulated flood depths to surveyed high-water marks. To complement direct evaluations of predicted depths at high-water marks, our techniques provide five additional metrics to assess modeled depths in areal sectors between the surveyed high-water mark and the stream channel. Our study also demonstrates a novel technique to evaluate flood predictions at damaged structures and crowd-sourced observations of flooded locations. The work in this study is part of a more complete evaluation of two hyper-resolution hydrologic models to generate street-level flood inundation predictions. We used the $679\text{-}{\mathrm{km}}^2$ Sugar Creek watershed above USGS Gage 02146800, near Fort Mill, SC, which contains the Charlotte, NC, municipal area. We assessed model performance at 172 surveyed high-water marks, 373 locations of flooded structures, and nearly 2,000 crowd-sourced observations of flooded locations. Results indicate that the analyses techniques help distinguish model performance and identify model deficiencies.

Riverbank filtration (RBF) is widely used in drinking water production all over the world. The horizontal and radial collector wells are among the most important water production facilities in case of the RBF aquifers. In this study several types of modeling methods are used to analyze the hydraulic conditions of horizontal and radial collector wells. The unsteady and steady-state flow in homogeneous, infinite, semi-infinite, and square-shaped bounded aquifers are investigated. The effect of delayed gravity response is modeled. Three-dimensional analytical and numerical finite-difference (FD) solution techniques are applied during the simulations to provide more reliable calculation results. Comparative analyses are carried out to optimize the wellbore drawdown in FD simulations. This important value is controlled by the local head loss due to the radial flow in vertical plane normal to the axes of screens. The multimesh FD simulation software FLOW is used for infinite and semi-infinite aquifers, while the MODFLOW Revised Multi-Node Well (MNW2) package is applied to the square-shaped aquifers. The late time partitioning (LTP) method is introduced to estimate the late time drawdown in infinite aquifers using semianalytical steady-state drawdown equations considering circular recharge boundaries. The latter value is derived by the semianalytical CW software. The use of results of various mostly analytically based solutions confirmed or improved the accuracy of the approximate numerical solutions. Such analytical support is vital for proper evaluation of the operation of horizontal and radial collector wells.

Probable maximum flood (PMF) has been used in large hydraulic infrastructure design for decades. However, a complete framework for deriving PMF with uncertainty analysis is lacking. This study investigates procedures ranging from probable maximum precipitation(PMP) with uncertainty to probable maximum storm (PMS), rainfall–runoff (R-R) with uncertainty, and PMF with uncertainty. A case study of Hurricane Harvey in the lower Brazos River basin in Texas is used to calibrate the R-R model and compare it with PMF. The uncertainty of PMF stems from these three components. The updated storm records indicate that except for the area size that drives PMP, the within-storm depth-area relation can generate depths greater than that of PMP for smaller areas, which runs counter to findings of a widely cited report. The PMF peak flow derived by the average PMP value was $\mathrm{12,716}{\mathrm{m}}^3/\mathrm{s}$, which was around three times the peak flow from Hurricane Harvey ($\mathrm{3,764}{\mathrm{m}}^3/\mathrm{s}$). The 95% PMP confidence interval band was 54.5 mm and resulted in a $\mathrm{3,656}{\mathrm{m}}^3/\mathrm{s}$ difference between the corresponding PMF peak flows. The return periods of PMP and rainfall of Harvey at a gauge station in Houston were around 400 years and 100 years, respectively, obtained from fitting either a generalized Pareto (GP) or generalized extreme value (GEV) probability distribution. For peak flow uncertainty, the PMP uncertainty accounted for most (81%) of the parts, while the R-R model uncertainty accounted for less (19%). The framework of this study can be expanded to other areas of interest having sufficient data sets.

Flood frequency analysis is the foundation for hydrological and hydraulic design, and fundamental to frequency analysis is the selection of a suitable probability distribution. This study therefore revisits the Halphen frequency distribution family, with parameters estimated by the maximum likelihood estimation (MLE) method and goodness-of-fit evaluated by the Kolmogorov-Smirnov (KS) test. Besides revising the Halphen family, this study (1) proposes the study of kurtosis to assist the selection of a probability density function; (2) applies the kernel density function as the parent distribution function to evaluate flood risk (using 100-year event as an example); and (3) evaluates the mixed Halphen distribution for the heavy-tailed peak flow falling into the Halphen-B region. Using 198 peak flow datasets selected from 18 hydrologic regions in 48 states in the continental US, the study showed that: (1) Halphen-A/Halphen-B distributions were the preferred distributions for 190 datasets; (2) the moment-ratio diagram was found to be a reliable indicator for selecting the appropriate distribution; (3) kurtosis may be a tool to assist with the distribution selection; (4) comparison and risk assessment indicated that the identified Halphen distributions may properly model the flood frequency distribution; and (5) overall, the study validated the applicability of Halphen distributions for flood frequency analysis.

This paper shows how low-impact development (LID) practices affect the resilience of stormwater drainage system under climate change scenarios. A rainfall-runoff model was calibrated and evaluated a in a tropical watershed located in Midwestern Brazil. An ensemble of 17 general circulation model outputs forced by Representative Concentration Pathways (RCP 4.5 and RCP 8.5) was used to create future climate change scenarios up to 2095. The LID efficiency was evaluated based on the runoff peak reduction and the resilience of stormwater drainage by means of a resilience index. Overall, LID combinations showed a reduction in runoff peak higher than 20%, and the best LID combination had a reduction of as much as 46%. This represents a significant improvement in the resilience against flooding in the study area. Therefore, the findings can contribute to the increase in widespread adoption of LID and can encourage decisionmakers to provide such practices for urban flood management.

In this study, rainfall time series data of 36 years collected at 33 meteorological stations were analyzed to introduce spatial and temporal characteristics of daily, monthly, and seasonal rainfall patterns for Northern Cyprus. For this purpose, concentration index (CI), precipitation concentration index (PCI), and seasonality index (SI) were employed. Additionally, the temporal trend of these indexes was evaluated using the Mann-Kendall (MK) trend test and innovative-Şen test (IŞT). Analyzing the temporal changes of rainfall patterns in the Eastern Mediterranean region is valuable to the whole area, where many countries are suffering from both water scarcity and increasing flash flood frequency. Therefore, the findings of this study were compared with the results of regional studies. The results of CI analysis show that Northern Cyprus has a moderately concentrated distribution of rainfall. On the other hand, the North Coast and Kyrenia Mountains regions are characterized by high annual rainfall as well as high risk of flood events. PCI and SI results show a greatly seasonal rainfall distribution pattern across the study area. Additionally, significant upward trends are observed in the majority of the stations in daily rainfall concentration.