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The variability of the second order moments of flood peaks with respect to geomorphoclimatic basin characteristics was investigated. In particular, the behaviour of the coefficient of variation <i>(Cv</i>) of the series of annual maximum floods was analysed with respect to its dependence on physically consistent quantities. The results achieved were in fairly good agreement with real world observed characteristics and interesting insights on the relationship between <i>Cv</i> and basin size were found. It appears that <i>Cv</i> is controlled mainly by the climate and by some water loss features. Many observations reported in the literature show a decrease of <i>Cv</i> with basin area <i>A</i>, usually ascribed to the limited spatial extent of extreme events, which leads to a decrease with area of the <i>Cv</i> of areal rainfall intensity. An increase of <i>Cv</i> with the area is also sometimes observed for small basins. Such different behaviours were accounted for by the concurrent effect on two parameters that affect the <i>Cv (A)</i> relationship, representative of the way rainfall losses and effective rainfall intensity scale with the basin area.</p> <p style='line-height: 20px;'><b>Keywords: </b>floods, climate, coefficient of variation, scaling.