Research on disasters by floods and geomorphological changes

为开展“洪涝灾害与地貌变化研究”，编制了三个分专题；(1)降雨和地表径流特征；(2)泥沙径流和河流变化特征；(3)海滩侵蚀特征。与主题(1)和(2)相关的讨论主要是关于布兰塔斯河的问题。第三个专题的重点是巴厘岛的珊瑚礁以及爪哇中北部的Semalan海滩。在进行研究时，采用了数据分析、数据收集观测和数值模拟。结果表明：(1)提出了一种长、短期降雨径流法，并利用Karankates水库径流资料对其适用性进行了验证。利用遥感影像和地理信息系统，实现了土地覆盖分类和地貌特征。降雨径流量采用运动波法计算，坡度和河道采用运动波法计算，支流产沙量采用单位水流功率法计算。(2)建立了考虑接触荷载、悬沙作用和支流输沙作用的一维和二维河流变化数值计算方法。该方法预测了河床的纵向变化、局部侵蚀形成凹河岸和河床物质的扩散，并应用于Brantas来评价河流的变化。此外，还提出了一种利用潮汐水库来减少河口沉积的方法。强调潮汐水库的光学调度可以防止河口严重淤积。(3)建立了一种基于二维控制方程和数据分析的海滩侵蚀方法。预测风致、浪致流和滩蚀过程。对人工养殖珊瑚礁的滩滩过程进行了数值模拟，并对河道缩短导致的沙量快速变化进行了预测。少

In order to conduct "research on disasters by flood and geomorphological changes", three sub-themes are prepared ;(1) Characteristics of rainfall and surface runoff,(2) Sediment runoff and river changes, and(3) Beach erosion.Discussions associated with topics (1) and (2) are made mainly on the problems in the Brantas river. The third topics is conducted with attention focused on the coral reef of Bali island as well as on the Semalan beach located on the north-central Jawa. In performing the study, data-analyzes, observations for data collections and numerical simulations are employed. Results are sammerized as follows :(1) A long and short terms rain fall runoff method its proposed in the upper Brantas, and is applicability is tested by using the runoff data at Karankates dam reservoir. Applying remote sensing images and a geographic information system, land cover classification and geomorphologic characteristics are realized. Rainfall runoff was computed by the kinematic wave method … More for the hillslopes and river channels, while sediment yields from tributaries was estimated by unit stream power method.(2) Numerical methods evaluating one dimensional river change as well as two dimensional one are developed, taking both contact loads and suspended sediment, and sediment supplies from tributaries into consideration. The methods predict longitudinal bed variation, local crosions forming concave river banks and propagation of bed material, and were applied to the Brantas to evaluate the river change. In addition, a method is proposed by means of a tidal reservoir for reducing the river mouth sedimentation. It emphasizes that optical operation of tidal reservoir prevents the river mouth from severe sedimentation.(3) A beach erosion method is developed, based on 2-D governing equations and data analyzes. It predicts wind-induced and wave-induced currents and beach crosion process. Numerical simulations have been conducted to predict the beach processes for cultivated coral reef as well as for rapid change of sediment supply due to shortcut of river course. Less