Assessing the Effects of Urban Landscape Area and Pattern Change on Flood Events in Qinhuai River Basin, China

Abstract

Urbanization significantly affects hydrological processes, but the influence level of urban landscape area change (ULAC) on flood magnitude has not been quantified, the response laws of floods with different characteristics to ULAC still needs further discussion, and the effects of urban landscape structure and shape on flooding have not been illustrated. This paper used a Markov chain and cellular automata (CA-Markov) model, the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) model, and the regression analysis method to assess the effects of ULAC on flooding. The Qinhuai River Basin (QRB) was selected to conduct the study. The results showed that (1) for minor, medium, and major flood groups, the statistical ranges of the linear curve [the relationship between flood volume (Qv) relative change and urbanization] slopes were 0.46–3.44, 0.74–1.82, and 0.24–0.76, respectively, whereas for peak flow (Qp) they were 0.8–3.27, 0.34–1.61, and 0.09–0.12, respectively; (2) the influence degree of ULAC on flood processes is gradually weakened with flood evolution; (3) for double-peak floods, the increase of the urban landscape area can significantly increase the Qp in the early stage and lead to earlier appearance of Qp, but for single-peak floods, the influence on peak time is not significant; and (4) urban landscape structure is more important than shape in terms of flood protection.