Analysis on the development characteristic of the Luoma Cave Underground River and the origin of the flood

According to the karst development history in the region, the formation and development of the Luoma Cave Subterranean River can be divided into two stages. The first stage occurred from the end of the Cretaceous Period to the late Tertiary Period. In this phase, precipitation was caught into the karst under-ground pipeline through the small karst depression and sinkholes located by the sides of the Woxiping polje, then drained into Woxiping polje and formed a small karst lake, and 3 east-westwards underground rivers formed at the same time. The second phase occurred from the end of the Tertiary Period until now. During this stage, with the uplift of the regional oscillated structure motion, the erosion base level declined continually. The Xiaheicao, Tongluoping and Woxiping sinkholes formed, and the east-west wards pipelines that formed in the early phase were transfixed and then the new pipeline captured the water from the karst lake, which made the dispersive karst water system discharged focused through the south-north wards pipeline and formed multi-entrance dendritic underground river system. The scale of the Luoma Underground River which formed in the later periodis too small and highly filled up that led to the discharging capacity get diminished, which is the main causation of the flood disaster in the polje. Based on this analysis, the governing way of the flood disaster in the drainage basin should include enhancing management of soil erosion, dredge river way and build new drainage tunnel.