Spatial moments of catchment rainfall: rainfall spatial organisation, basin morphology, and flood response

Abstract

Abstract. This paper describes a set of spatial rainfall statistics (termed "spatial moments of catchment rainfall") quantifying the dependence existing between spatial rainfall organisation, basin morphology and runoff response. These statistics describe the spatial rainfall organisation in terms of concentration and dispersion statistics as a function of the distance measured along the flow routing coordinate. The introduction of these statistics permits derivation of a simple relationship for the quantification of catchment-scale storm velocity. The concept of the catchment-scale storm velocity takes into account the role of relative catchment orientation and morphology with respect to storm motion and kinematics. The paper illustrates the derivation of the statistics from an analytical framework recently proposed in literature and explains the conceptual meaning of the statistics by applying them to five extreme flash floods occurred in various European regions in the period 2002-2007. High resolution radar rainfall fields and a distributed hydrologic model are employed to examine how effective are these statistics in describing the degree of spatial rainfall organisation which is important for runoff modelling. This is obtained by quantifying the effects of neglecting the spatial rainfall variability on flood modelling, with a focus on runoff timing. The size of the study catchments ranges between 36 to 982 km 2 . The analysis reported here shows that the spatial moments of catchment rainfall can be effectively employed to isolate and describe the features of rainfall spatial organization which have significant impact on runoff simulation. These statistics provide useful information on what space-time scales rainfall has to be monitored, given certain catchment and flood characteristics, and what are the effects of space-time aggregation on flood response modeling.

A framework for assessing hydrological regime sensitivity to climate change in a convective rainfall environment: a case study of two medium-sized eastern Mediterranean catchments, Israel

“…The role of rainfall variability is even greater in climate regimes where a substantial portion of rainfall is convective and runoff is sensitive to this type of rainfall (Morin and Yakir, 2014;Rozalis et al, 2010;Smith et al, 2000;Yakir and Morin, 2011). The hydrological response was found to be sensitive to rainfall spatial variability in very small catchments (less than 1 km 2 ; Bahat et al, 2009), in catchments of few dozen km 2 (Zoccatelli et al, 2011) and larger catchments (> 100 km 2 ; Arnaud et al, 2011). It is therefore essential to use rainfall data with high spatial and temporal resolution Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Extreme flood response to short-duration convective rainfall in South-West Germany

“…The catchment-scale storm velocity has therefore an implicit hydrological meaning. Zoccatelli et al (2011) showed that an upbasin (downbasin) velocity is associated to a decrease (increase) of flood peak with respect to an equivalent stationary storm. A finding which is often reported is that the effect of storm motion on flood peak is maximized when storm velocity has similar magnitude as the channel flow velocity (Singh, 1998;Seo et al, 2012).…”

“…Among these, the direction and the speed of the storm motion with respect to the catchment morphology is probably the most important one (Seo et al, 2012). To examine in a quantitative way these aspects, we use here the concept of "catchment scale storm velocity" proposed by Zoccatelli et al (2011) and based on the spatial moments of catchment rainfall. These statistics, which build on previous work by Viglione et al (2010) and correspond in part to the catchment rainfall statistics reported in Smith et al (2002Smith et al ( , 2005, assess the dependence of the catchment flood response on the space-time interaction between rainfall and the spatial organization of catchment flow pathways.…”

“…The spatial and temporal rainfall characteristics are examined here by using the spatial moments of catchment rainfall (Zoccatelli et al, 2011). As a detailed description of the method and of its assumptions is reported in Zoccatelli et al (2011), only an outline of the method is given here.…”

“…As a detailed description of the method and of its assumptions is reported in Zoccatelli et al (2011), only an outline of the method is given here. With these statistics, rainfall spatial variability is examined relative to a distance metric imposed by the so-called "flow distance", i.e.…”