Effect of storm movement on flood peaks: Analysis framework based on characteristic timescales

The aim of this paper is to investigate, in general terms, the effects of storm movement on the resulting flood peaks, and the underlying process controls. For this purpose, we utilize a broad theoretical framework that uses characteristic time and space scales associated with stationary rainstorms as well as moving rainstorms. For a stationary rainstorm the characteristic timescales that govern the peak response include two intrinsic timescales of a catchment and one extrinsic timescale of a rainstorm. On the other hand, for a moving rainstorm, two additional extrinsic scales are required, the storm travel time and storm size. The relationship between the peak response and the timescales appropriate for a stationary rainstorm can be extended in a straightforward manner to describe the peak response for a moving rainstorm. However, the interdependence between rainfall duration and storm travel time makes the behavior of the peak response for a moving rainstorm fundamentally different from that of a stationary rainstorm. We show that the relationship between peak response and characteristic timescales also depends on the relative size of the rainstorm with respect to catchment size. For moving rainstorms, we show that the augmentation of peak response arises from both the effect of overlaying the responses from subcatchments (resonance condition) and the effect of increased responses from subcatchments due to increased duration (interdependence), which results in maximum peak response when the moving rainstorm is slower than the channel flow velocity.