Abstract
Rainfall exhibits substantial variability, and its temporal resolution considerably affects simulation of hydrological processes. This study aims to investigate the effect of the temporal resolution of rainfall (TRR) on urban flood modeling and to explore how high TRR is required. A routing-enhanced detailed urban stormwater (REDUS) model, which has four layers and accounts for complex urban flow paths, was developed and then applied to the campus of Tsinghua University, Beijing, China. For 30 rainfall events at 1-min resolution, the rainfall accuracy index (RAI) was used to describe the discrepancy of rainfall patterns by upscaling. Through hydrodynamic modelling, the effect of TRR was quantified by the relative error of flood volume and peak in typical areas. The results show that (1) flood peak is sensitive to TRR while flood volume is generally not; (2) with lower TRR, discharge peak is underestimated, and a power function is proposed to express the relationship between the effect of TRR and the characteristics of rainfall and underlying surfaces; and (3) rainfall data of 5-min resolution for urban areas smaller than 1 km2, or at least 15-min resolution for larger areas, are required to constrain the relative biases of flood peak within 10%.
Highlights
Rainfall is one of the key drivers of urban hydrological process and demonstrates high temporal and spatial variability [1]
This paper aims to investigate three questions: (1) What are the effects of temporal resolution of rainfall (TRR) on simulation of flood processes when using a detailed urban hydrodynamic model, especially for urban areas smaller than 3 km2 ? (2) What is the relationship between the effect of TRR and the characteristics of rainfall and underlying surfaces? and (3) How high TRR can meet the demands for accurate urban flood modelling?
The rainfall–runoff relationship first analyzed at grid scale based on the simulation results of 1-min rainfall, whichrelationship is necessarywas to first understand effectscale of TRR
Summary
Rainfall is one of the key drivers of urban hydrological process and demonstrates high temporal and spatial variability [1]. In 1997, Singh [2] summarized how the hydrograph is affected by the temporal and spatial distribution of rainfall and identified that the influence of rainfall depends on watershed characteristics Rainfall variability makes it important to adopt an appropriate rainfall resolution to model hydrological response, especially in urban catchments with short response time [3,4]. Variogram analysis was conducted theoretically to describe temporal (or spatial) variability as the characteristic scale, which was defined as the temporal (or spatial) distance by which two individual points show statistical independence [3] Based on this method, Berne et al [10] proposed the relationship between the required characteristic scales of rainfall and urban catchments, and derived the required rainfall resolution for urban hydrological applications. Emmanuel et al [11] summarized
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