A Copula-Based Multivariate Probability Analysis for Flash Flood Risk under the Compound Effect of Soil Moisture and Rai
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A Copula-Based Multivariate Probability Analysis for Flash Flood Risk under the Compound Effect of Soil Moisture and Rainfall Ming Zhong 1 & Ting Zeng 1 & Tao Jiang 1 & Huan Wu 2,3 & Xiaohong Chen 4 & Yang Hong 5 Received: 17 June 2020 / Accepted: 2 November 2020/ # Springer Nature B.V. 2020
Abstract
Flash floods can be characterized by several variables. Of these, soil moisture (SM) is an important environmental factor that plays a key role in hydrological and ecological processes and affects the mechanisms that cause flash floods. To more accurately determine the occurrence probability of flash floods, the combined effects of soil moisture and rainfall indexes were considered in this paper, and the copula function approach was explored for use in joint probability analyses of flash flood risks. The results showed that (1) the Clayton copula function offered the best fit for the bivariate joint distribution and captured the occurrence probability of the combination of both peak flow (PF) and SM, while the t-copula function achieved the best fit for the multivariate joint distribution, which presented different combinations of characteristic flash flood parameters. (2) The joint distribution probability of flash floods increased with increasing risk parameter thresholds. Return period analysis indicated that the return periods of the bivariate joint distribution were smaller than those of the multivariate joint distribution. (3) If PF and SM are fixed, the occurrence probability of flash floods is higher in regions where the maximum 1-h rainfall is higher. This study provides an effective and quantitative approach to improving flash flood prediction and advances the application of this approach for the management of future flash flood risks. Keywords Copula function . Combination of risk probability . Flash floods . Multivariate joint distribution . Soil moisture
1 Introduction Flash floods refer to local flooding hazards caused by sudden rainstorms or massive snowmelt and are one of the most common natural disasters occurring in the world. Flash flood disasters
* Tao Jiang [email protected] Extended author information available on the last page of the article
Zhong M. et al.
eventually have devastating impacts on life and economic growth in a country and can result in severe damage to and loss of infrastructure and properties as well as human fatalities (Eugene et al. 2019). The causes of flash floods, in general, are complex and include a combination of natural and anthropogenic factors, including hydrological factors, geological factors, geomorphological characteristics, and anthropological activities (Gan et al. 2018). Among them, rainfall is often considered the major cause of flash flood events in small-scale watersheds (Ma et al. 2020). Early warnings based on rainfall thresholds are essential to predicting flash flood occurrences and have been demonstrated as helpful for reducing flood damage (Gourley et al. 2014; Zhang et al., 2013). Moreover, several studies have suggested that soil moisture (
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