Technological innovation has brought spatial reorganization of production systems in the electrom ics industry in Japan since the 1980s. Especially on the fringes of metropolitan regions, some main fac-tories owned by large corporations have made serious change in their factories' functions. Thus, it is necessary to disentangle linkages of subcontractors in those regions from a spatial viewpoint.
The purpose of this study was to elucidate the linkage system of a large electronics factory located in the fringe of the Keihin area, which consists of Tokyo, Kawasaki, Yokohama and their suburban re-gions, and which contains the largest concentration of electronics factories in Japan. The Ome plant of Company T, located in the western part of the Keihin area, was chosen because company T is one of the largest electronics manufacturers in Japan. To reveal linkages between the Ome plant and its first-tier subcontractors, and between first-tier and second-tier subcontractors, the author conducted interviews with executive officers at the Ome plant and at the headquarters of Company T, and questionnaire surveys at each first-tier subcontractor, in 1992. There were 45 first-tier subcontractors and 138 second-tier ones.
The Ome plant was established in 1968 to produce computers, but its intra-firm function has shifted from production to research and development. In order to keep producing at this site, the Ome plant was forced to rationalize its production. Parts requiring high skill levels were processed and assembled at the plant, and final assembly was performed. Numerous other processes and assem-blies that did not require high levels of skill depended on first-tier subcontractors. Company T's sub-sidiaries supplemented first-tier subcontractors within the linkage system of the Ome plant. The policy decision was that the higher value-added activities would remain within the Ome plant itself. First-tier subcontractors undertook less profitable process or products, Agreements with first-tier subcontractors served to lower variable costs and surplus investment in equipment. Company T's policy on the use of the subcontract system is to shift short-term costs to subcontractors by means of inter-subcontractor competition and intensification of orders to specific subcontractors.
Although many first-tier subcontractors are located in the fringe of Keihin Area, we found a some-what wide spatial dispersion among them. There were two regional differences in subcontracts: one was used in the Keihin area, where specialized processing techniques were used; the other was used in peripheral regions, where large-scale and standardized production was undertaken. Some spatially dispersed plants were established as branches by the first-tier subcontractors in the Keihin area. This fact indicates that Company T at Ome is responding to increasing demands without establishing a mass-production plants.
In considering transactional relationships, first-tier subcontractors did not always depend on the Ome plant for processing techniques. The subcontractors accumulate their own technology or tech-niques, and have many business relationships among themselves and with other large machinery firms located in the Keihin area. In the process of increasing transactions with large firms, the first-tier subcontractors spatially dispersed toward regions far from the Keihin area.
The first-tier subcontractors depended on second-tier subcontractors in many production processes. By intention of subcontract, second-tier linkages were divided into two categories: one was related to specialized techniques and equipment, the other to cheap labor cost. The former type of linkage was especially seen in orders to Keihin's second-tier subcontractors. This means that there was a strict dependence on an existing agglomerated area with technical processes in a lower tier of the pro-duction system.

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Previous studies in the Japanese mountains have suggested that slope failure plays a significant role in determining the structure of drainage networks. However, few studies have examined the ef-fects of slope failure on Horton's parameters of drainage nets such as the bifurcation ratio and the stream length ratio. To address the question, this paper examines the drainage nets of mountain river basins in the Matsumoto region of central Japan, which are subject to frequent slope failure (Fig. 1). Two types of drainage nets were constructed on topographic maps: “D-type drainage”-iden-tified from deeply notched v-shaped contours with angle<53° and “T-type drainage”-flow lines along shallower valleys combined with the D-type drainage (Figs. 2 and 3). The comparison between the constructed drainage nets and geomorphological maps has revealed that the D-type drainage mostly occurs in deep valleys cutting into the bedrock, whereas the T-type one generally occurs both in the deep valleys and in shallow hollows caused by regolith failure (Table 2).
Horton's law of stream numbers and lengths generally holds for both D-type and T-type drainages (Figs. 4 and 5) . Mean bifurcation ratios for both drainage types exceed the theoretical values report-ed in previous works (4.0), and occasionally reach 5.0. Mean stream length ratios tend to be less than 2. 0, although the theoretical ratios are 2.0 to 2.3 (Table 3) . The T-type drainage has larger bifur-cation ratios and smaller stream length ratios than the D-type one, showing stronger disagreement with the theoretical values.
Further analyses on both types of drainage nets have shown that “excess streams”, which do not con-tribute to increase in stream orders despite their joining, abundantly exist on the valley-side slopes of high-order streams (Table 4). The number of excess streams is larger than that of the most proba-ble drainage nets deduced from mathematical theory. This fact accounts for the increased number of low-order streams, and thus for the large values of mean bifurcation ratios. Stream length ratios be-tween 1st- and 2nd-order streams are much smaller than those between higher-order streams (Fig. 5, Table 3), indicating that the low values of mean stream length ratios reflect the notably large length of 1st-order streams. These tendencies are more distinct for the T-type drainage than for the D-type one.
The unique drainage structure in the study area is ascribed to the frequent occurrence of storm-induced slope failure, the most dominant erosion process in the region. Because slope failures left many hollows and gullies on valley sides of high-order streams, the number of low-order streams in-creased. Failures also led to the migration of channel heads toward upper hillslopes, resulting in elon-gated 1st-order streams. Because the T-type drainage reflects the effects of shallow failure more direct-ly, it has larger bifurcation ratios and smaller stream length ratios than the D-type one.
To examine the validity of the above inference, the known values of the bifurcation ratio and the stream length ratio for various regions were compiled (Table 6). Most of the values had been calculat-ed for the drainage nets including small channels, identified by T-type contour crenulation, field sur-veys, and aerial-photo interpretation. The compilation has revealed that the bifurcation ratios and the stream length ratios for the Matsumoto region are comparable to those for other Japanese moun-tains. By contrast, river basins subjected to less frequent slope failure, such as those in Japanese non-mountainous areas and foreign countries, have smaller bifurcation ratios and larger stream length ratios than those in Japanese mountains. These findings validate the hypothesis that widespread slope failure leads to larger bifurcation ratios and smaller stream length ratios.

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The purpose of this report is to arrange the definitions of geomorphometric measures for digital ele-vation models (DEMs) and to prescribe some advanced applications of the 50 m-DEM newly deli-vered by the Geographical Survey Institute of Japan.
We express terrain surface morphology in the two forms of computer-compatible data structure. One is the vector type, in which the surface is defined as a set of local triangular patches, or contour lines. The other is the raster type as a two-dimensional array of even-spaced terrain heights (DEM). In the report we focus our interest on the geomorphometric measures for DEMs.
The measures can be classified into three types by localization of objects: point, window, and drain-age-basin. The window measures are statistical parameters of heights within the scanning window, and they are plotted at central points of the windows resulting in raster maps of geomorphometry.
To calculate drainage-basin measures it is necessary to prepare anteriorly the drainage direction matrix (DDM). The DDM is a raster map in which the drainage direction (related to the neighbor-ing lowest point) is indicated by the chain code of the rook's or queen's case. We are not concerned here with the interesting skill of automatic generation of DDM from DEM.
The drainage-basin measures are the same as the window measures in definition, but they are plot-ted at outlet points of the basins, and therefore resulted also in raster maps of basin geomorphome-try.
Newly defined measures in this report include projected area (A), surface area (A_S), and volume (V) of topography defined within the window and the drainage basin, and their derivatives for ex-ample, general steepness (A/A_S), general relief (V/A), and steepness index (V/A^3/2).

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