| Abstrakt: |
Explaining the response of catchments with a mix of pervious and impervious surfaces requires the inclusion of controls other than catchment imperviousness. In this study, we made use of a large sample of 70,227 events in 852 U.S. catchments to analyze the interplay of total impervious area (TIA) and antecedent soil moisture (ASM) in determining the event runoff ratio (RR). First, we investigated the importance of TIA as a spatial control compared to other catchment attributes (describing climate and catchment landscape) in explaining the differences between catchments in terms of median event‐scale RR. Second, we examined the importance of ASM as a temporal control of the variability of RR in comparison with spatial settings and event characteristics. Third, events were grouped into 30 classes of TIA and 30 classes of ASM, and linear regression models were used to analyze the evolution of RR depending on each one of the two independent variables. Results showed the following: (1) Analysis of the importance of space‐varying catchment descriptors highlighted the relevance of TIA as a control of catchment response, whereas ASM showed a stronger ability compared to other event characteristics. (2) ASM played a significant role in urbanized catchments as in rural ones. The absence of abrupt changes in the linear model parameters indicates that the impact of urbanization on the relationship between RR and ASM was relatively gradual. (3) Differences in RR between rural and intensively urbanized catchments were observable not only for dry pre‐event conditions but also for wet short‐term conditions. Plain Language Summary: Urbanization causes a substantial increase in surface sealing which leads to dramatic impacts on water cycle. Reliable projections of the impact of urbanization require a good understanding of the multiple factors that shape the response of a catchment along a wide range of urbanization levels. In catchments with a mix of urban and natural areas, the interplay of total impervious area (TIA) and antecedent soil moisture (ASM) conditions is still not well elucidated. To fill this gap, we attempted to quantify the relative importance of TIA and ASM in determining the event‐scale catchment response using a sample of 852 U.S. catchments. We found that both controls play an important role in runoff generation. Particularly, ASM should be considered even in catchments with a high level of urban cover. We also found that the impact of TIA on runoff ratio was relatively gradual and became significant when TIA exceeded 5%. This study provides a solid empirical understanding of the behavior of urbanized catchments, which is a step toward more reliable prediction of the impact of urbanization on hydrology for urban planning policies. Key Points: Runoff ratio was dependent not only on imperviousness but also on antecedent soil moisture conditions, even in highly urbanized catchmentsCatchment imperviousness and antecedent soil moisture had the best ability in explaining the spatiotemporal variability of runoff ratioImpact of total impervious area on runoff ratio became significant when mean catchment imperviousness exceeded 5% [ABSTRACT FROM AUTHOR] |
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