Controls on the Spatial and Temporal Patterns of Rainfall‐Runoff Event Characteristics—A Large Sample of Catchments Across Great Britain

Abstract

AbstractThis study reveals the spatiotemporal variability of event characteristics and their controls from 290,743 rainfall‐runoff events across 431 Great Britain catchments. Metrics characterizing event runoff coefficient, event timescale and normalized peak discharge and their mean, variability and seasonality statistics are extracted to quantify event characteristics. Using random forest models, we find climate attributes are most influential in controlling the spatial pattern, with land cover, geology and soil properties also playing a critical role especially for explaining the variability of event runoff response. Rainfall characteristics (particularly rainfall depth) exhibit dominant controls on the temporal dynamic at event scale, while catchment initial state (antecedent soil moisture) determines its seasonal variations. Clear regional patterns of event characteristics are observed in Great Britain, while the influences of geology and anthropogenic activities on local differences are detected. Extremely low runoff coefficient values (<0.05) but with high variability are typical in Chalk catchments in Southeast region. Flashy events with short event timescale (<10 hr) and less seasonality of runoff response are observed in urban catchments. A large reservoir close to a gauge leads to the reduction of peak flows, yet the deviation is relatively small in summer. The impact of surface water abstractions is not obvious in our data set, whereas the impact of groundwater abstractions largely reflects the geology. This study provides the basis for regionalization studies by revealing the (dis)similarities of catchment runoff response and emphasizes the need for further research into the role of geology and human activities on rainfall‐runoff characteristics.