Two-dimensional Hydraulic Model Research Articles

The utility of HEC-1 flood hydrograph package in distributed flow guided area drainage master plan discharges verification in a desert environment

Flood control management and policies that formed the foundation of the Upper New River Area Drainage Master Plan Development in Phoenix, Arizona, USA, took into account engineering, environmental, landscape, social, and economic considerations. In this engineering-in-practice focused paper, the authors verify the accuracy of the existing condition 100-year, 24-hour rainfall event design discharges by superimposing them on the existing probabilistic discharge envelope curves derived for the region by various US Government agencies over the last five decades. The US Army Corps of Engineers' HEC-1 flood hydrograph package has been the choice of the local flood control district since 1987 when the first flood insurance study (FIS) was conducted on the catchment. The HEC-1 model results accorded well with those on the various discharge envelope curves originally derived from gauged catchments. The computed peak discharges were adjusted using the results from a two-dimensional FLO-2D hydraulic model to account for the existing flow breakout locations and man-made storage areas in the post-FIS in-channel sand and gravel mine pits. The approach was a novel and timely undertaking by the modellers in support of robust flood control alternatives development.

Hydraulic and Sediment Transport Simulation of Koiliaris River Using the MIKE 21C Model

The objective of this work is the simulation of the water depth, flow velocity and sediment transport in the downstream part of the Koiliaris River (Crete – Greece). The two-dimensional hydraulic model MIKE 21C is used, which has been developed specifically to simulate 2D flows and morphological changes in rivers. The model is based on an orthogonal curvilinear grid and comprises two parts: (a) the hydrodynamic part which is based on the Saint-Venant equations and (b) the morphological change part for the sediment transport. The curvilinear grid and bathymetry files were generated using a very high resolution DEM (1 m x 1 m). Time series discharge data from a hydrometric station and a 2D map of initial surface water elevation were also introduced as input parameters in the hydrodynamic part of the model. Regarding the sediment transport model, field measurements of the sediment characteristics and the suspended sediment concentration were used. The model was calibrated and verified using water level field data and sediment concentration data that were collected during high and low flow discharges. Model simulation was in good agreement with field observations as indicated by a variety of statistical measures. The results of the model were 2D maps of flow velocity, water depth, sediment transport and bed level changes. Using the obtained simulation results, extreme hydrological events such as droughts or floods transporting large sediment loads, can be monitored in the study area.

Comparison between Curvilinear and Rectilinear Grid Based Hydraulic Models for River Flow Simulation

In the present work, the two-dimensional hydraulic models MIKE 21 and MIKE 21C were used in order to simulate the water depth at the downstream section of the Koiliaris River Basin in Crete-Greece. Specifically, an important goal of the present study was the comparison of the widely used MIKE 21 with the MIKE 21C model. The MIKE 21C model has been developed specifically to simulate 2D flows and morphological changes in rivers. It is based on an orthogonal curvilinear grid and comprises two parts: (a) the hydrodynamic part that is based on the Saint-Venant equations and (b) the morphological change part for the simulation of sediment transport. In contrast to model MIKE 21C, the general version of MIKE 21 is based on a rectilinear grid. The difference between the curvilinear and the rectilinear grid is that the curvilinear grid lines follow the bank lines of the river, providing a better resolution of the flow near the boundaries. The water depth results of the two models were compared with field observations and a series of statistical indicators. It was concluded that the curvilinear grid based model results were in better agreement with the field measurements.

Analysis of Hydraulic Effect by River Dredging in a Meandering Channel

This paper attempted to analyze the hydraulic effects that the dredging can take as an alternative to reduce possible damages of flooding due to the overflow of river levee in meandering rivers, where riverbed aggradation, seepage and erosion may occur. In order to make a hydraulic analysis in a section of meandering rivers, a two-dimensional hydraulic analysis model, RMA-2, was selected. The GIS was applied to construct two-dimensional finite element grids to consider the hydraulic conditions before and after dredging. The water surface elevations, depths, velocities, and tractive forces were compared before and after the dredging. The difference of water surface elevation between the inside and outside of river was turned out to be the maximum value of 0.58m under the design flood condition. It could be evaluated that the tractive force at the bank decreased about 42 to 67% on average for all the sections. These results could give valuable information that the dredging of the stream channel at the meandering sections decreased the risk of overflow, seepage and erosion of the banks. The methodologies given in this study will contribute to mitigating the flood damages in the surrounding farmlands.

Paleoflood discharge reconstruction in Tatra Mountain streams

Floods represent a common process in Tatra Mountain streams and may cause flood risk in the valleys of the Tatra foreland. Dealing with the hazards and risks caused by floods requires a detailed analysis of the frequency and magnitude of past and recent events. However, the Polish Tatra region is characterized by a scarcity of data on past floods in general and on systematic peak discharge in particular. In this study, we performed a paleohydrological analyses in four high-gradient mountain streams using scarred trees as paleostage indicators. We couple two-dimensional hydraulic modelling in a highly-resolved topographic environment (LiDAR data) with an important spatiotemporal data set of scars on trees to investigate (i) the magnitude of unrecorded major floods of the twentieth century, (ii) the effect of variability in geomorphic tree positions on the peak discharge reconstruction, and (iii) the impact of reconstructed events on the results of flood frequency analyses. The data set is based on a total of 55 scarred trees and allows peak discharge reconstruction of 16 major floods covering the last 113years. Results suggest that trees growing in straight stream reaches or in the inner side of channel bends would be better candidates for peak discharge reconstructions than trees located on the outer side of channel bends or growing in overbank sections with dense vegetation cover. The largest reconstructed flood is dated to 1903 with an estimated peak discharge of 115.9±59.2m3s−1, and larger-than-today floods are found to have occurred at Strążyska and Łysa Polana in the first half of the twentieth century. The inclusion of our results into the flood frequency analyses suggests that flood hazards might have been underestimated by up to 25.5% in the case of a 100-year flood in Strążyski Stream. In that sense, our findings will be useful for the design of future strategies dealing with flood risks in the foreland of the Polish Tatra Mountains.

Flood Inundation Analysis and Mitigation with a Coupled 1D-2D Hydraulic Model: A Case Study in Kochi, Japan

Coupled one and two-dimensional (1D-2D) hydraulic models play a significant role in analyzing flooding problems to find possible solutions as they can reproduce the actual situations relatively accurately. This paper summarizes approaches to flood inundation analysis and mitigation with coupled 1D-2D hydraulic models of a small mountain watershed in Japan. A detailed flood inundation model including the effects of drainages, pumping, inflow from mountain sub-watersheds and flood gates is developed using coupled 1D-2D hydraulic models. The model is applied to the inundation in Kubokawa, a small town in Kochi Prefecture, Japan on August 9-10, 2014. Simulated and observed maximum water levels along the river and maximum inundations in the flood plain are compared and found to be consistent. Causes of the flooding and percentage of contribution are quantitatively identified, and countermeasures to reduce the effects of flooding are proposed.

Hydraulic Experiments on Transmission Coefficients for Vertical Structure under Intermediate Water Depth Condition

본 연구에서는 직립식 구조물의 ì „ë‹¬íŒŒê³ ê³„ìˆ˜ ì‚°ì •ì„ 위한 2차원 수리실험을 실시하였다. 불규칙파를 ìž ì‚¬íŒŒë¡œ ì ìš©í•˜ì˜€ìœ¼ë©° 직립식 구조물에 대한 ì „ë‹¬íŒŒê³ ê³„ìˆ˜ ì‚°ì •ì‹ì„ ì œì•ˆí•˜ê³ , Goda(1969) 등의 결과와 비교하였다. Goda(1969)의 결과는 ìž ì‚¬íŒŒë¡œ 규칙파를 ì ìš©í•œ 결과로서 불규칙파를 ì ìš©í•œ 본 실험의 결과와 차이를 보였다. Goda의 결과가 본 연구에 비하여 크게 ì „ë‹¬íŒŒê³ ê³„ìˆ˜ë¥¼ ì œì‹œí•˜ëŠ” 것을 알 수 있었다. 또한 Goda는 직립벽에 대하여 í‰ê· , 상한 및 하한에 대한 계수값을 ì œì‹œí•˜ì˜€ìœ¼ë‚˜(d = h ì¡°ê±´), 본 연구에서는 각각의 설계요소(구조물 폭, 수심, 파장 등)가 ì „ë‹¬íŒŒê³ ê³„ìˆ˜ì— 주는 영향을 계수를 통하여 ì •ëŸ‰ì ìœ¼ë¡œ ì œì‹œí•˜ì˜€ë‹¤. 또한 ì—¬ìœ ê³ ê°€ 0인 조건에 대한 에너지보존 및 ì „ë‹¬íŒŒê³ íŠ¹ì„±ì„ ì œì‹œí•˜ì˜€ë‹¤. 핵심용어: 직립식 구조물, ì „ë‹¬íŒŒê³ ê³„ìˆ˜, 2차원 수리실험, 불규칙파

Two-Dimensional Coupled Distributed Hydrologic–Hydraulic Model Simulation on Watershed

The objective of this work is to develop a coupled distributed model that enables to analyze water movement in watershed as well as analyze the rainfall-runoff. More specifically, it allows to estimate the various hydrologic water cycle variables at each point of the watershed. In this paper, we have carried out a coupled model of a distributed hydrological and two-dimensional hydraulic models. We have incorporated a hydrological rainfall-runoff model calculated by cell based on the Soil Conservation Service (SCS) method to the hydraulic model, leaving it for the hydraulic model (GUAD2D) to conduct the transmission to downstream cells. The goal of the work is demonstrate the improved predictive capability of the coupled Hydrological-Hydraulic models in a watershed.

Evaluation of the U.S. Geological Survey standard elevation products in a two-dimensional hydraulic modeling application for a low relief coastal floodplain

Summary Growing use of two-dimensional (2-D) hydraulic models has created a need for high resolution data to support flood volume estimates, floodplain specific engineering data, and accurate flood inundation scenarios. Elevation data are a critical input to these models that guide the flood-wave across the landscape allowing the computation of valuable engineering specific data that provides a better understanding of flooding impacts on structures, debris movement, bed scour, and direction. High resolution elevation data are becoming publicly available that can benefit the 2-D flood modeling community. Comparison of these newly available data with legacy data suggests that better modeling outcomes are achieved by using 3D Elevation Program (3DEP) lidar point data and the derived 1 m Digital Elevation Model (DEM) product relative to the legacy 3 m, 10 m, or 30 m products currently available in the U.S. Geological Survey (USGS) National Elevation Dataset. Within the low topographic relief of a coastal floodplain, the newer 3DEP data better resolved elevations within the forested and swampy areas achieving simulations that compared well with a historic flooding event. Results show that the 1 m DEM derived from 3DEP lidar source provides a more conservative estimate of specific energy, static pressure, and impact pressure for grid elements at maximum flow relative to the legacy DEM data. Better flood simulations are critically important in coastal floodplains where climate change driven storm frequency and sea level rise will contribute to more frequent flooding events.

Analysis of Water Quality Impact for Water Intake in Jinyang Reservoir Using CE-QUAL-W2

Hydraulic and water quality models with high reliability are necessary for the efficient management of water quality in the reservoir. The model capacity can be demonstrated by the application for the various hydrological conditions. CE-QUAL-W2 model is laterally averaged two-dimensional hydraulic and water quality model. The W2 model, which is suitable for the narrow reservoir like the Jinyang reservoir as compared with the depth and length of waterbody, has been frequently used by many researchers. Namgang watershed is expected to increase the water demand. In this study, the W2 model is validated under two different hydrological conditions; wet year (2011) and normal year (2009). Using hydrological and water quality condition for calibration, 2011, the effect of water intake increase was simulated. The simulation results showed that the increase of water intake led to increase the concentrations in total nitrogen, total phosphorus and Chlorophyll- concentration. Especially the concentration increase was appeared during the dry season in each of up to 62.53% (Total nitrogen), 39.07% (Total phosphorus) and 232.19% (Chlorophyll-). The changes of chlorophyll- is similar to those of total phosphorus concentration.

Ecohydraulics in applied river restoration: a case study in the San Marcos River, Texas, USA

The Upper San Marcos River is home to Texas wild rice (Zizania texana), an endangered aquatic macrophyte. Introduced aquatic plants Hydrilla verticillata and Hygrophila polysperma now occupy over 45% of the areal distribution. A two-dimensional hydraulic model was integrated with biological response functions for Zizania, Hydrilla, and Hygrophila to predict optimal locations for Zizania currently occupied by Hygrophila or Hydrilla. At these locations, non-native plants were manually removed and Zizania planted over approximately 20–50% of the exposed areas. Fixed grid locations were monitored bi-weekly over the next year to document plant responses. Monitoring showed a high success rate of expanding Zizania areal coverage and reductions in the non-native species distributions in restoration areas. Utilization of hydraulic modeling to direct spatially explicit aquatic plant restoration activities was shown to be an effective approach with a high success rate at identified restoration sites in the San Marcos River.

Does small-bodied salmon spawning activity enhance streambed mobility?

Female salmonids bury and lay their eggs in streambeds by digging a pit, which is then covered with sediment from a second pit that is dug immediately upstream. The spawning process alters streambed topography, winnows fine sediment, and mixes sediment in the active layer. The resulting egg nests (redds) contain coarser and looser sediments than those of unspawned streambed areas, and display a dune-like shape with an amplitude and length that vary with fish size, substrate conditions, and flow conditions. Redds increase local bed surface roughness (<10−1 channel width, W), but may reduce the size of macro bedforms by eroding reach-scale topography (100–101W). Research has suggested that spawning may increase flow resistance due to redd form drag, resulting in lower grain shear stress and less particle mobility. Spawning, also prevents streambed armoring by mixing surface and subsurface material, potentially increasing particle mobility. Here we use two-dimensional hydraulic modeling with detailed prespawning and postspawning bathymetries and field observations to test the effect of spawning by small-bodied salmonids on sediment transport. Our results show that topographical roughness from small salmon redds has negligible effects on shear stress at the reach-unit scale, and limited effects at the local scale. Conversely, results indicate sediment mixing reduces armoring and enhances sediment mobility, which increases potential bed load transport by subsequent floods. River restoration in fish-bearing streams should take into consideration the effects of redd excavation on channel stability. This is particularly important for streams that historically supported salmonids and are the focus of habitat restoration actions.

TWO DIMENSIONAL NUMERICAL MODELING OF FLOW IN TRAPEZOIDAL BEND CHANNEL USING SPUR DIKE

A two-dimensional hydraulic flow model was developed using the SMS software (Surface Water Modeling System) to simulate the flow properties(thalweg line location) for meander in trapezoidal section channel, and its changes when a single emerge spur dike install at mid of the bend. The model was calibrated and verified through matching velocity profiles throughout the study reach. Thalweg line location were found due to the variation of spur dike characteristic including 180 runs, included five different ratios of spur dike length to top channel width (L/Tw), five ratios of spur dike arm to its body length (l/L), and two spur arm`s direction for four different flow rates, as a result, through the flow configuration the new location of the thalweg in the bend channel after using the spur dike was about (44-71)%Tw which mainly affected by spur body length.

Integration of 2-D hydraulic model and high-resolution lidar-derived DEM for floodplain flow modeling

Abstract. The rapid progress of lidar technology has made the acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially in regards to the study of floodplain flow. However, high-resolution DEM data pose several disadvantages for floodplain modeling studies; e.g., the data sets contain many redundant interpolation points, large numbers of calculations are required to work with data, and the data do not match the size of the computational mesh. Two-dimensional (2-D) hydraulic modeling, which is a popular method for analyzing floodplain flow, offers highly precise elevation parameterization for computational mesh while ignoring much of the micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, thus enabling the calculation of flood water levels in DEM grid cells through local inverse distance-weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha detention basin, which is a flood storage area of Dongting Lake in China, by using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than simulations only with DEM.

Uncertainty in Various Habitat Suitability Models and Its Impact on Habitat Suitability Estimates for Fish

Species distribution models (SDMs) are extensively used to project habitat suitability of species in stream ecological studies. Owing to complex sources of uncertainty, such models may yield projections with varying degrees of uncertainty. To better understand projected spatial distributions and the variability between habitat suitability projections, this study uses five SDMs that are based on the outputs of a two-dimensional hydraulic model to project the suitability of habitats and to evaluate the degree of variability originating from both differing model types and the split-sample procedure. The habitat suitability index (HSI) of each species is based on two stream flow variables, including current velocity (V), water depth (D), as well as the heterogeneity of these flow conditions as quantified by the information entropy of V and D. The six SDM approaches used to project fish abundance, as represented by HSI, included two stochastic models: the generalized linear model (GLM) and the generalized additive model (GAM); as well as three machine learning models: the support vector machine (SVM), random forest (RF) and the artificial neural network (ANN), and an ensemble model (where the latter is the average of the preceding five models). The target species Sicyopterus japonicas was found to prefer habitats with high current velocities. The relationship between mesohabitat diversity and fish abundance was indicated by the trends in information entropy and weighted usable area (WUA) over the study area. This study proposes a method for quantifying habitat suitability, and for assessing the uncertainties in HSI and WUA that are introduced by the various SDMs and samples. This study also demonstrated both the merits of the ensemble modeling approach and the necessity of addressing model uncertainty.

Two-dimensional physical habitat modeling of effects of habitat structures on urban stream restoration

River corridors, even if highly modified or degraded, still provide important habitats for numerous biological species, and carry high aesthetic and economic values. One of the keys to urban stream restoration is recovery and maintenance of ecological flows sufficient to sustain aquatic ecosystems. In this study, the Hongje Stream in the Seoul metropolitan area of Korea was selected for evaluating a physically-based habitat with and without habitat structures. The potential value of the aquatic habitat was evaluated by a weighted usable area (WUA) using River2D, a two-dimensional hydraulic model. The habitat suitability for Zacco platypus in the Hongje Stream was simulated with and without habitat structures. The computed WUA values for the boulder, spur dike, and riffle increased by about 2%, 7%, and 131%, respectively, after their construction. Also, the three habitat structures, especially the riffle, can contribute to increasing hydraulic heterogeneity and enhancing habitat diversity.

Evaluation of Steelhead Passage Flows Using Hydraulic Modeling on an Unregulated Coastal California River

Passage and habitat connectivity flows for steelhead Oncorhynchus mykiss through depth sensitive natural, low gradient, critical riffle sites were investigated in the unregulated Big Sur River, California. The River2D two-dimensional hydraulic habitat model, along with quantitative passage metrics and species-specific and lifestage-specific depth criteria, were used to evaluate and compare predicted fish passage flows with flows derived by a traditional empirical critical riffle fish passage method. Passage flows were also compared with historical unimpaired natural hydrology patterns to assess the frequency and duration of suitable passage flows under the naturally variable flow regimes characteristic of Central California coastal rivers. A strong relationship (r 2 = 0.93) was observed between flows predicted by hydraulic modeling and flows identified by the empirical critical riffle method. River2D provided validation that the flows derived using the traditional critical riffle methodology provided for contiguous passable pathways of suitable hydraulic (depth and velocity) conditions through complex cobble-dominated riffle sites. Furthermore, steelhead passage flows were spatially and temporally consistent between lagoon and upstream riffles for adults, and were generally indicative of a river system in equilibrium with a naturally variable flow regime and associated intact ecological processes. An analysis of 25years of continuous flow data indicated sufficient flows for upstream passage by young-of-year and juvenile steelhead were produced between 37% and 100% and between 1% and 95% of the time, respectively. September and October are the most challenging months for natural flows to meet young-of-year and juvenile passage and habitat connectivity flows. Careful consideration of seasonal and interannual flow variability dynamics, therefore, are critical components of an effective flow management strategy for the maintenance and protection of passage and habitat connectivity flows between lagoon and upriver habitats. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Hydraulic modeling of the 2011 New Madrid Floodway activation: a case study on floodway activation controls

Engineered floodways are floodplains managed by hydraulic controls that can be activated passively, whereby the floodway fills and empties with changes in channel stage, or through a rapid control action, such as the detonation of a levee. During May of 2011, the Birds Point-New Madrid Floodway (NMF) was activated through levee detonation and the performance of this approach is examined herein. A two-dimensional hydraulic flood model (LISFLOOD-FP) is applied to the NMF and calibrated for April and May of 2011 in order to recreate the levee detonation scenario (detonation control). Additionally, the model is applied to simulate flood impacts had the NMF been activated passively, without the deliberate breaching of the levees (passive control). Results show that detonation control reduced flood stages upstream of the activation site by 0.8 m (2.62 ft) without significantly altering overall flooding extent compared with the passive control scenario. Damage estimates from the US Federal Emergency Management Agency HAZUS-MH model indicate that detonation control slightly reduced losses associated with building replacement costs and damaged crops (4.0 % reduction). However, floodway and levee damages that occurred under the detonation control required over 50 million US$ in repairs, and these costs would have been greatly reduced under a passive control scenario. These results indicate that the detonation control effectively reduced flood stage and the risk of upstream levee failures without increasing flooding extent, building losses, and crop damages, but the potential for floodway erosion and deposition deserves additional consideration in the implementation of a rapid activation design.

Assessing the operation rules of a reservoir system based on a detailed modelling chain

Abstract. According to available climate change scenarios for Belgium, drier summers and wetter winters are expected. In this study, we focus on two multi-purpose reservoirs located in the Vesdre catchment, which is part of the Meuse basin. The current operation rules of the reservoirs are first analysed. Next, the impacts of two climate change scenarios are assessed and enhanced operation rules are proposed to mitigate these impacts. For this purpose, an integrated model of the catchment was used. It includes a hydrological model, one-dimensional and two-dimensional hydraulic models of the river and its main tributaries, a model of the reservoir system and a flood damage model. Five performance indicators of the reservoir system have been defined, reflecting its ability to provide sufficient drinking water, to control floods, to produce hydropower and to reduce low-flow conditions. As shown by the results, enhanced operation rules may improve the drinking water potential and the low-flow augmentation while the existing operation rules are efficient for flood control and for hydropower production.

Virtual manipulation of topography to test potential pool–riffle maintenance mechanisms

In this study, numerical experimentation with two-dimensional hydraulic modeling of pool–riffle river topography drawing on the testbed data from the classic Keller (1971) study was used to investigate the effect of synthetically manipulating topography on the occurrence and magnitude of velocity and Shields stress reversals in a pool–riffle sequence. Reversals in velocity and shear stress have been used to explore mechanisms of pool–riffle maintenance, while Shields stress (a combined measure of transport capacity and substrate erodibility) is emerging in importance. The original site topography was modeled alongside six altered ones to evaluate the sensitivity of hydraulic reversals to subtle morphology — five incrementally wider pools and a filled pool. The Caamaño (2009) criterion, a simplified geometric threshold for predicting velocity reversals, was applied to each terrain to evaluate its utility. The original pool–riffle topography was just over the threshold for a velocity reversal and well over the threshold for a strong Shields stress reversal. Overall, pool widening caused a predominantly local response, with change to pool hydraulics and no change in section-averaged velocity in the riffle beyond the initial widening of 10%. Filling in the pool significantly increased the magnitude of reversals, whereas expanding it eliminated the occurrence of a reversal in mean velocity, though the Shields stress reversal persisted because of strong differentiation in bed material texture. Using Shields stress as a reversal parameter enabled the quantification of pool modification effects on pool–riffle resiliency. The Caamaño (2009) criterion accurately predicted reversal occurrence for the altered terrains with exaggerated effects, but failed to predict the weak reversal for the original topography. Two-dimensional modeling coupled with previously accepted hydrologic, geomorphic, and engineering analyses is vital in project design and evaluation prior to construction.