Channel Flow Routing Research Articles

A GIS‐ASSISTED DISTRIBUTED WATERSHED MODEL FOR SIMULATING FLOODING AND INUNDATION1

ABSTRACT: A distributed watershed model combining kinematic wave routing, 1‐D dynamic channel‐flow routing, and 2‐D diffusive overland‐flow routing has been developed to simulate flooding and inundation levels of large watersheds. The study watershed was linked to a GIS database and was divided into an upstream mountainous area and a downstream alluvial plain. A kinematic wave routing was adopted at the mountainous area to compute the discharge flowing into the alluvial plain. A 1‐D dynamic channel routing solving the St. Venant equations by the Preissmann method was performed for the main channel of the alluvial plain, whereas a 2‐D overland‐flow routing solving the diffusion wave equation with the Alternating Direction Explicit scheme was used for floodplains. The above two routings were connected by weir‐link discharge formula. The parameters in the model were calibrated and independently verified by single‐event storms. An example application of flooding/inundation analysis was conducted for the Taichung station and the Woozi depot (Taiwan High Speed Rail). Suggested inundation‐proofing measures ‐ including raising ground surface elevation of the station and depot and building a waterproofing exterior wall and their combination ‐ were investigated. It was concluded that building the waterproofing exterior wall had a strong tendency to decrease peak inundation depth.

Development and application of a spatially-distributed Arctic hydrological and thermal process model (ARHYTHM)

A process-based, spatially distributed hydrological model was developed to quantitatively simulate the energy and mass transfer processes and their interactions within arctic regions (arctic hydrological and thermal model, ARHYTHM). The model first determines the flow direction in each element, the channel drainage network and the drainage area based upon the digital elevation data. Then it simulates various physical processes: including snow ablation, subsurface flow, overland flow and channel flow routing, soil thawing and evapotranspiration. The kinematic wave method is used for conducting overland flow and channel flow routing. The subsurface flow is simulated using the Darcian approach. The energy balance scheme was the primary approach used in energy-related process simulations (snowmelt and evapotranspiration), although there are options to model snowmelt by the degree-day method and evapotranspiration by the Priestley–Taylor equation. This hydrological model simulates the dynamic interactions of each of these processes and can predict spatially distributed snowmelt, soil moisture and evapotranspiration over a watershed at each time step as well as discharge in any specified channel(s). The model was applied to Imnavait watershed (about 2·2 km2) and the Upper Kuparuk River basin (about 146 km2) in northern Alaska. Simulated results of spatially distributed soil moisture content, discharge at gauging stations, snowpack ablations curves and other results yield reasonable agreement, both spatially and temporally, with available data sets such as SAR imagery-generated soil moisture data and field measurements of snowpack ablation, and discharge data at selected points. The initial timing of simulated discharge does not compare well with the measured data during snowmelt periods mainly because the effect of snow damming on runoff was not considered in the model. Results from the application of this model demonstrate that spatially distributed models have the potential for improving our understanding of hydrology for certain settings. Finally, a critical component that led to the performance of this modelling is the coupling of the mass and energy processes. Copyright © 2000 John Wiley & Sons, Ltd.

An integrated, physically based model for arid region flash flood prediction capable of simulating dynamic transmission loss

This paper outlines a physically based model developed for prediction of both arid region flash floods and associated transmission loss. It is based on coupling numerical solutions of the St Venant equations and the kinematic wave equation for channel and overland flow routing, respectively, with the Richards' equation for the determination of infiltration. These hydrological components are integrated in one comprehensive model for the above-mentioned purposes. The robustness of the model and its components have been tested and it has then been applied to a medium-size catchment in an arid region. The results indicate that reasonable simulations can be achieved with a minimum of calibration, but point to problems of representing input rainfall conditions with the necessary time and space resolutions. © 1998 John Wiley & Sons, Ltd.

Flood routing based on diffusion wave equation using mixing cell method

A one-dimensional non-linear diffusion wave equation is derived from the Saint Venant equations with neglect of the inertia terms. This non-linear equation has no general analytical solution. Numerical schemes are therefore employed to discretize the space and time axes and convert the differential equation to difference form. In this study, the mixing cell method is used to convert the diffusion wave equation to difference form, in which the difference term can be eliminated by selecting an optimal space step size Δx when time step size Δt is given. When the time step size Δt → 0, the space step size Δx = Q/(2S 0 BC k ) where Q is discharge, S 0 is bed slope, B is channel width and C k is kinematic wave celerity, which is the same as the characteristic length proposed by Kalinin and Milyukov. The results of application to two cases show that the mixing cell and linear channel flow routing methods produce hydrographs that are in agreement with the observed flood hydrographs.

Kinematic wave modeling in water resources: surface-water hydrology

Water Resources Modeling. Spatial Representation of Watersheds. HYDRAULIC PRELIMINARIES. Hydraulic Equations for Surface Flow. Linearization of Hydraulic Equations. Flow Resistance. WATER WAVES. Shallow Water Waves. Kinematic Wave Theory. Diffusion Wave Theory. Accuracy of Kinematic Wave and Diffusion Wave Theories. OVERLAND FLOW. St. Venant Equations for Flow Over A Plane. Diffusion Wave Modeling. Kinematic Wave Modeling of Overland Flow on A Plane: Analytic Solutions. Kinematic Wave Modeling of Overland Flow on an Infiltrating Plane: Analytical Solutions. Kinematic Wave Modeling of Overland Flow on a Plane: Numerical Solutions. Kinematic Wave Modeling of Overland Flow on Converging Surfaces. Kinematic Wave Modeling of Overland Flow on Diverging Surfaces. Kinematic Shock. CHANNEL FLOW ROUTING. Dynamic Wave Modeling for Channel Flow Routing. Diffusion Wave Modeling for Channel Flow Routing. Kinematic Wave Flow Routing. Dam--Break Flood--Wave Routing. Appendices. References. Index.

A FRAMEWORK FOR PHOSPHORUS TRANSPORT MODELING IN THE LAKE OKEECHOBEE WATERSHED1

ABSTRACT: A modeling framework was developed to determine phosphorus loadings to Lake Okeechobee from watersheds located north of the lake. This framework consists of the land‐based model CREAMS‐WT, the in‐stream transport model QUAL2E, and an interface procedure to format the land‐based model output for use by the in‐stream model. QUAL2E hydraulics and water quality routines were modified to account for flow routing and phosphorus retention in both wetlands and stream channels. Phosphorus loadings obtained from previous applications of CREAMS‐WT were used by QUAL2E, and calibration and verification showed that QUAL2E accurately simulated seasonal and annual phosphorus loadings from a watershed. Sensitivity and uncertainty analyses indicated that the accuracy of monthly loadings can be improved by using better estimates of in‐stream phosphorus decay rates, ground water phosphorus concentrations, and runoff phosphorus concentrations as input to QUAL2E.

RASTER‐BASED HYDROLOGIC MODELING OF SPATIALLY‐VARIED SURFACE RUNOFF1

ABSTRACT: The proliferation of watershed databases in raster Geographic Information System (GIS) format and the availability of radar‐estimated rainfall data foster rapid developments in raster‐based surface runoff simulations. The two‐dimensional physically‐based rainfall‐runoff model CASC2D simulates spatially‐varied surface runoff while fully utilizing raster GIS and radar‐rainfall data. The model uses the Green and Ampt infiltration method, and the diffusive wave formulation for overland and channel flow routing enables overbank flow storage and routing. CASC2D offers unique color capabilities to display the spatio‐temporal variability of rainfall, cumulative infiltrated depth, and surface water depth as thunderstorms unfold. The model has been calibrated and independently verified to provide accurate simulations of catchment response to moving rainstorms on watersheds with spatially‐varied infiltration. The model can accurately simulate surface runoff from flashfloods caused by intense thunderstorms moving across partial areas of a watershed.

Design hydrology and sedimentology for small catchments

Introduction. Hydrologic Frequency Analysis. Rainfall-Runoff Estimation in Stormwater Computations. Open Channel Hydraulics. Hydraulics of Structures. Channel Flow Routing and Reservoir Hydraulics. Sediment Properties and Sediment Transport. Erosion and Sediment Yield. Sediment Control Structures. Fluvial Geomorphology: Fluvial Channel Analysis and Design. Ground Water. Monitoring Hydrologic Systems. Hydrologic Modeling. Chapter Problems, References, and Appendixes. General Appendix. Subject Index.

A stochastic integral equation analog of rainfall-runoff processes for evaluating modeling uncertainty

In this paper a very general rainfall-runoff model structure (described below) is shown to reduce to a unit hydrograph model structure. For the general model, a multi-linear unit hydrograph approach is used to develop subarea runoff, and is coupled to a multi-linear channel flow routing method to develop a link-node rainfall-runoff model network. The spatial and temporal rainfall distribution over the catchment is probabilistically related to a known rainfall data source located in the catchment in order to account for the stochastic nature of rainfall with respect to the rain gauge measured data. The resulting link node model structure is a series of stochastic integral equations, one equation for each subarea. A cumulative stochastic integral equation is developed as a sum of the above series, and includes the complete spatial and temporal variabilities of the rainfall over the catchment. The resulting stochastic integral equation is seen to be an extension of the well-known single area unit hydrograph method, except that the model output of a runoff hydrograph is a distribution of outcomes (or realizations) when applied to problems involving prediction of storm runoff; that is, the model output is a set of probable runoff hydrographs, each outcome being the results of calibration to a known storm event.

Analytical representation of cross-section hydraulic properties

An alternative power function representation of hydraulic properties for one-dimensional flow routing in channels with compound cross-sections is put forward. The hydraulic properties of interest are cross-section flow area, wetted perimeter and conveyance factor. The independent variable is flow depth. The alternative power function representation is continuous with flow depth and it follows the trend of suddenly changing hydraulic property values at overbank elevation. It is applicable to a large range of complex section shapes which may include overbank channels, natural levees and minor channel irregularities such as sand bars and small terraces where traditional simple power functions have failed. The alternative power function representation is simple and highly efficient from the computational point of view. Its performance is illustrated for several actual compound cross-sections. Efficiency and extended capabilities make it an attractive procedure for one-dimensional channel flow routing in drainage networks where hydraulic properties of many cross-sections need repeated evaluation.

An Approximation for the Bank Storage Effect

A perturbation procedure is used to calculate an approximate flood‐routing solution for the coupled groundwater and open channel flow equations. Seepage is initially neglected to calculate the solution of the linearized kinematic wave equations. The kinematic wave solution is then used to obtain a solution for the groundwater problem, and this groundwater solution is used to obtain a second‐order solution for the flood‐routing problem. The solution has a relatively simple form that is easily applied, and an example suggests that changes created in the downstream hydrograph by bank storage can be of the same order as changes created by retaining all terms in the open channel flow equations and routing the flood down the channel with zero bank storage.

Kinematic Wave Routing and Computational Error

The standard kinematic wave (KW) method used in many models of open channel flow routing of runoff hydrographs in watershed models is examined as to the significance of the computational errors due to numerical‐diffusion and the selection of computational effort. It is shown that a wide range of modeling results are possible from a KW model depending on the choice of computational reach length and time‐step size used in the KW approximation. In comparison, the simple convex hydrologic routing method demonstrates only a small fraction of the variation in results demonstrated by the KW model. It is recommended that use of the KW method for channel routing in watershed models be reconsidered.

Urban Runoff Digital Computer Model

A digital computer model for small urban watersheds has been developed. The model utilizes a numerical solution of the kinematic wave equations for overland flow and channel flow routing. The runoff from pervious areas is estimated by utilizing appropriate infiltration curves whose initial and final infiltration rates are varied depending upon the soil type and moisture conditions. The model works satisfactorily with big storm events when utilizing rainfall data of an Hawaiian small urban watershed. With selected design storm patterns, the model is useful for new designs of storm drainage systems and to evaluate existing storm drainage systems.