Abstract:Metal contents of sediments in Manila Bay -Laguna Lake watershed in the Philippines were measured and detailed horizontal distribution was obtained. The distribution of zinc and lead concentration in Manila Bay clearly shows the effect of anthropogenic contamination and it was explained by the diffusion of lead and zinc rich anthropogenic particles discharged from Pasig River. The sediments in Laguna Lake were mostly natural particulate matters from surrounding mountains and they contained 20 mgPb/kg and 100 mgZn/kg, while the sediment taken at the heavily polluted branches of the Pasig River contained as high as 88 mgPb/kg and 310 mgZn/kg. The lead and zinc concentrations in the sediments of Manila Bay -Laguna Lake watershed were compared with those in the mouth of the Tama River, Tokyo, where the faster deposition of coarser natural origin particles and slower deposition of lead and zinc rich anthropogenic particles determined the sediment concentration. The comparison was also made with Hanoi City, Vietnam. In spite of the difference in time when leaded gasoline was prohibited, the difference in the lead concentrations of roadside deposits and sediments was not obvious in the vicinity of these three target cities. This is probably due to dilution by a large amount of suspended solids conveyed by the Pasig River in the case of the Philippines. Storm water runoff containing roadside deposits and discharge of untreated wastewater were identified as factors increasing zinc and lead concentrations of sediments in receiving waters based on the measurements on roadside deposits and the estimation of the contribution of untreated wastewater.

Hydraulic physical model experiments concerning the inundation by river water in Kyoto City are carried out to clarify the characteristics of the behavior of flooding water on a complicated city area. The physical model scale is 1/100 and it is a non-distorted model. The model can make allowance for the intrusion of flooding water into underground space. Flooding processes were simulated by using a numerical model that incorporated the finite volume method and unstructured meshes. The flooded area and depth of water in case of no intrusion of flooded water into underground space were reasonably well evaluated by this method, while in case of intrusion of water into underground space calculated results were not well evaluated. The reason is that the drop flow equation was used to estimate the discharge into underground space and that the entrances into underground space were not taken into account reasonably.The suitable equation for evaluating the discharge into underground space must be developed and also the unstructured mesh of entrances must be constituted reasonably.Key Words: flood disaster in urban cities, inundation due to river flood, hydraulic physical model experiment, inundation in underground space, numerical simulation, Kyoto City