Actual Conditions of Terrain Roughness Evaluated from Numerical Data of Structural Dimensions in Tokyo

The terrain roughness in the 23 wards of Tokyo cannot be easily evaluated because of a variety of structures with different dimensions. The authors have characterized the city from the viewpoint of terrain roughness, using the numerical data of dimensions of all structures in the 23 wards. The area of the 23 wards was divided into about 2,600 regions with a 500m mesh, and the terrain roughness of each region was analyzed. The results indicate that the regions are classified into the following three groups; that is, (i) regions in which the ratio Rf≥4 of the building area to the mesh area for the buildings with four stories or over is less than 20%, (ii) regions in which 20%≤ Rf≥4