ANTECEDENT MOISTURE CONDITION (SCS) FREQUENCY ASSESSMENT: A CASE STUDY IN SOUTHERN ITALY

Abstract

ABSTRACT This paper reports on a procedure used to define the joint probability distribution of two hydrological variables describing a meteoric event: the maximum intensity of the rain and the accumulation in the antecedent five days. The main goal is to define the frequency of occurrence of the three antecedent moisture condition classes of the SCS‐CN method connected to extreme intensity rain events, with reference to a very precise data set containing records with aggregation time of 10 min. In order to define the relation between the hydrological variables, the marginal distribution of the two variables was first identified and afterwards the global dependency structure was studied through the copula function. Afterwards, according to data collected from rain gauge stations located in the Campania region, in southern Italy, and selecting peak‐intensity rain events higher than 20 mm h –1 , the evidence was that the AMCI class is the most frequent, rather than the AMCIII class (the frequency of which is never above 26% in the vegetal dormant season and 12% in the vegetal growing season). Such results lead to the conclusion that using the AMCIII class in design calculation, mainly in dry areas (like southern Italian regions), is not particularly suitable, while the use of AMCII is more advisable. Copyright © 2013 John Wiley & Sons, Ltd.