Takao Tamura

AN INUNDATION INSIDE THE LEVEE ANALYTICAL METHOD THAT CONSIDERED THE BASE FLOW OF THE DRAINAGE CANAL

An inundation inside the levee analytical method that considered the base-flow of the drainage canal was considered for the suburban area where the mountainous district and the field were contained, and the drainage-canal flowed. The base-flow is presumed from the unsteady flow calculation using the waterlevels data of the drainage-canal observed at low-water, and applied to an inundation inside the levee model. The analytical method of the present study was applied to inundation inside the levee in Nishisuga region in Tokushima city that had been generated by Typhoon No.11 in 2014. The following results were achieved. (1)The water-levels in drainage-canal could be reproduced when it was flooded. (2)The runoffcoefficient presumed by the analytical modeling and the runoff-coefficient calculated from material concerning the land-uses were roughly corresponding. (3)The ratio of the base-flow at the flood peak was estimated to be about 50%. The importance of the evaluation of the base-flow was suggested.

A METHOD FOR ESTABLISHING STAGE-DISCHARGE CURVE BY USING RAINFALL, WATER LEVEL DATA AND RUNOFF MODEL

A method for establishing stage-discharge curve (H-Q curve) using a runoff model to the rainfall observed in a basin and the water level observed in a river channel was discussed. A quadratic function that represented the relation between water level and discharge was built into the runoff model. When the observed water level hydrographs at some floods were reproduced, the H-Q curve was obtained. The method was applied to six water level stations in Shikoku which observed runoff quantity, and the established curve was compared with the H-Q curve based on the runoff observation. Two major findings were obtained: (1) a satisfied H-Q curve in which the error was 5-17% compared with measurement H-Q curve could be set up by using the data of one main flood event when there was a rain-gauge stations for each 30km 2 in the basin or more; (2) a useful H-Q curve was still obtained by using a lot of flood events when the rain-gauge stations were sparse and were unevenly distributed.

MATHEMATICAL MODELING OF NITRATE NITROGEN RUNOFF PROCESS FROM A FORESTED BASIN WITH NITRIFICATION SUB MODEL

A mathematical model of NO3-N runoff process from a forested mountain basin is developed, based on a tank model comprising a surface tank with soil water storage systems, and a ground water tank. The model takes account of three elementary processes of NO3--N in the forested mountain soil. They are infiltration and advection, solute exchange between mobile water and immobile regions, and nitrification by microorganisms in the soil. The process of former two are modeled as a function of the rainwater movement and soil moisture saturation calculated by the tank model. The latter process is modeled as a function of soil temperature calculated by a soil temperature model. The model is applied to annual observations in 1992 obtained in Shirakawa-tani forested mountain basin (main species Japanese cedar ) located on Shikoku island in Japan. The model describes the seasonal change of NO3-N streamwater concentration well, through a year.

The Runoff Analysis of Total Nitrogen and Phosphorus in a Storm Event in a Forested Basin Using a Tank Model

This study focused on the runoff characteristic of total nitrogen and phosphorusduring a storm event in a forested basin. The stream water was separated into four runoff components using a tank model, and the correlation between those components and the temporal changes of stream water concentration of total nitrogen and phosphorus was investigated. It is clarified that stream water concentration of total nitrogen and phosphorus are formed by the temporal change of runoff components. Then, the modeling of runoff of total nitrogen and phosphorus from a forested basin is employed using a tank model.