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Title:The effect of rainstorm movement on urban drainage network runoff hydrographs
Author(s):Seo, Yongwon
Director of Research:Schmidt, Arthur R.
Doctoral Committee Chair(s):Garcia, Marcelo H.
Doctoral Committee Member(s):Schmidt, Arthur R.; Kumar, Praveen; Sivapalan, Murugesu
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Storm movement
Runoff hydrographs
Stochastic channel network model
Abstract:Prediction and estimation of runoff has been a long-standing topic of hydrology for the purpose of water resources management both in terms of quality and quantity, flood control, ecology, and environmental considerations. It is well recognized that surface runoff from a watershed due to a rainstorm varies with the hydro-meteorological characteristics of the rainfall and the physiographic properties of the watershed. The direct influence of rainfall movement on the shape of a runoff hydrograph has been known for a long time. However, previous studies and research regarding moving rainstorms are mostly based on a specific catchment, which was either synthetic or real. The study of a single specific catchment makes it difficult to extrapolate our understanding of the effects of storm movement to different watersheds. Therefore, instead of focusing on a specific catchment or rainfall condition, this study seeks to establish a generalized relation between rainstorm movement and runoff hydrographs based on network configuration. This study utilizes a conceptual model based on characteristic timescales to investigate the effects of storm movement on the flood peak flows, and the underlying process controls. A broad theoretical framework is developed that uses characteristic time and space scales associated with stationary rainstorms as well as moving rainstorms. This study explores the relations between network configurations and hydrograph sensitivity to storm kinematics; storm speeds, storm directions, and storm sizes. The configuration of the drainage network is simulated with Gibbs’ model. The peak response is investigated with different rainstorm conditions and network configurations. The results show that the effect of the direction and speed of the rainstorm movement significantly depends on network properties. The relation between storm kinematics and the peak discharge response is dependent on network configuration; accordingly network efficiency. Mass balance analysis in an urban watershed indicates that rainfall infiltrated to pervious areas might contribute to direct runoff hydrograph, thereby offering an explanation for the long hydrograph tail. Width functions are obtained from urban drainage networks and applied to obtain distinct response functions for Direct Connected Impervious Areas (DCIA), Isolated Impervious Areas (IIA), and pervious areas combined with excess and infiltrated amount of rainfall. This methodology addresses the mass balance error observed in runoff hydrographs in urban watersheds based on two assumptions regarding the contribution of pervious areas to runoff hydrographs. The results show improvement in the estimation of runoff hydrographs and suggest the need to consider the flow contribution from infiltrated rainfall amount in pervious areas to the flow discharge hydrograph. The results also imply that additional contribution from flow paths such as pipe infiltration needs to be considered. In addition, this study investigates the applicability of stochastic network models to urban drainage network in terms of runoff hydrographs. The actual network is replaced by stochastic networks from the Monte-Carlo simulation and the hydrologic response function is developed using synthetic width functions from Gibbs’ model. The results indicate that the simulated network with the stochastic network model can be a good approximation of an actual network in terms of runoff hydrographs at the outlet of the watershed. Finally, by introducing the Equivalent Stationary Storm (ESS) compared with moving rainstorms, this study evaluates the effect of rainstorm movement on the peaks discharge response. This study shows that the drainage networks in urban areas have wide range of network configuration and they can be highly inefficient in terms of drainage time compared with natural channel networks. However, the result shows that inefficient networks are less sensitive to rainstorm movement and as a consequence, they potentially contribute to mitigate the effect from rainstorm movement in urban catchments. This research evaluates the effect of rainstorm movement and also reproduces the discharge hydrograph based on the network configuration. Therefore, the framework of this study strongly suggests a generalized relation between the storm movement and hydrologic response of an urban catchment based on its network configuration. It also implies an optimal balance between network efficiency and safety to storm kinematics that leads to potential improvement in urban drainage networks.
Issue Date:2012-05-22
Rights Information:Copyright 2012 Yongwon Seo
Date Available in IDEALS:2012-05-22
Date Deposited:2012-05

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