Abstract
The effects of rainfall and underlying surface conditions on flood recession processes are a critical issue for flood risk reduction and water use in a region. In this article, we examined and clarified the issue in the upper Huaihe River Basin where flood disasters frequently occur. Data on 58 rainstorms and flooding events at eight watersheds during 2006–2015 were collected. An exponential equation (with a key flood recession coefficient) was used to fit the flood recession processes, and their correlations with six potential causal factors—decrease rate of rainfall intensity, distance from the storm center to the outlet of the basin, basin area, basin shape coefficient, basin average slope, and basin relief amplitude—were analyzed by the Spearman correlation test and the Kendall tau test. Our results show that 95% of the total flood recession events could be well fitted with the coefficient of determination (R2) values higher than 0.75. When the decrease rate of rainfall intensity (Vi) is smaller than 0.2 mm/h2, rainfall conditions more significantly control the flood recession process; when Vi is greater than 0.2 mm/h2, underlying surface conditions dominate. The result of backward elimination shows that when Vi takes the values of 0.2–0.5 mm/h2 and is greater than 0.5 mm/h2, the flood recession process is primarily influenced by the basin’s average slope and basin area, respectively. The other three factors, however, indicate weak effects in the study area.
Highlights
Flooding is a natural phenomenon and will become a serious natural hazard when its water volume reaches a certain magnitude (Sayers et al 2002; Alfieri et al 2014)
The results show that 95% of the total flood recession events can be well fitted with R2 values greater than 0.75
By selecting eight watersheds in the upper mountainous area of the Huaihe River Basin, we examined the impacts of rainfall and the underlying surface on flood recession processes
Summary
Flooding is a natural phenomenon and will become a serious natural hazard when its water volume reaches a certain magnitude (Sayers et al 2002; Alfieri et al 2014). A flooding event includes both the rising period and the recession period. The former is closely connected to rainfall, especially the maximum rainfall rate and the time to the centroid of a rainfall event (Shuster et al 2008). Shuster and his colleagues proposed that a more precise time step was needed to note the rising period, which means that less precise temporal resolution data could not capture the variability in the stage that was to be expected with the short-term flow phenomena of the rising limb rate. The flood recession period, which typically is longer than 1/2 of an entire flooding event, is more important for water use (Shorr 2000; Guan et al 2014), because a flood could provide abundant water resources (Shao et al 2009; Ahmad et al 2014; Liu et al 2015)
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