Kazuhisa Matsunaga, Shinya Kouno

Present Condition Survey of the Urban Area in KOBE-CITY,Japan

The earthquake disaster reconstruction work carried out since 1995 in Kobe city, Japan has been steadily progressing. However, there are areas considerably disused and poorly developed such as roads entering urban areas. This paper describes the current situation of urban areas, using the city planning foundation's survey data along with the town district unit, to tackle future city planning.

1.Introduction

On 17th January 1995, a strong vertical-thrust earthquake (The Great Hanshin -Awaji Earthquake) struck Kobe city, leading to a great loss of life and extensive damage to essential services. There was tremendous damage to roads, railroads, buildings and power lines. Since then the city residents and businesses of Kobe city have joined efforts to focus on post-quake reconstruction and now residential life is slowly returning to normal.

After the Great Hanshin -Awaji earthquake, the effectiveness of GIS has become widely recognized in Japan and has rapidly spread. From 1992 onwards, even Kobe city's Planning Department's planning division has made varied use of GIS and has digitalized the information obtained from 1/2500 topographical maps and regulatory systems. Within this, the "U-map" system which carries out inspection of regulatory system information (involving land use and construction), plays a role in the improvement of citizen services as well as reducing labor costs.

To gather basic data collection and analysis targeted towards restoration of Kobe city, this survey used GIS in ascertaining road maintenance conditions (highways and secondary roads) and indexed it to examine the current situation of urban areas.

2.Survey outline

2.1.Reference limits of the survey

The reference limits of the survey makes planned redevelopment of the city redevelopment policy necessary for this urban area (Diagram 1).

Diagram 1

2.2.System structure

This survey made use of ArcView8.1 for data processing and analysis, and for examining the results, ArcView3.2 and ArcView8.1 were used (Diagram 2).

Diagram 2

2.3.GIS Data

This survey used the GIS data shown in the table.

Table 1. showing the GIS data used

Elements	Information level of map	Method of preparation
Topographical map(1/2500DM)	2500	Renewed by aerial photo survey
Regulatory system information	2500	Regulatory system zones entered as polygon data
Road polygon	2500	Roads extracted from topographical maps (1/2500DM) are converted into polygon data and divided by a representative width
Central road line	2500	Central road lines entered as line data
Building lot polygon	2500	Land use maps entered as polygon data
Block polygon	10000	Block area converted into Polygon data
Division polygon	10000	District polygon integrated into Town level

3.Result of survey

3.1.Total Unit

The town polygon was treated as the total unit of the survey.

3.2.Current situation of highways

Roads of over 12m in width which prevented fires in the Great Hanshin-Awaji earthquake were examined in the following order:

Table 2. Classification of density of roads over 12m in width

Method of classification	Color classification
Less than 1.5sq km	Red
More than 1.5sq km,less than 2.5sq km	Orange
More than 2.5sq km,less than 3.5sq km	Yellow
More than 3.5sq km,less than 4.0sq km	Green
More than 4.0sq km,less than 6.0sq km	Light blue
More than 6.0sq km	Red

Diagram 3

3.3.Understanding the present conditions for district of roads

Roads having densities of more than 400m/ha or having more than 50% of roads less than 4m were classified in the following order.

Diagram 4

4.Conclusion

By digitalizing Kobe city's current situation as GIS data, road maintenance in the Targeted districts could be understood objectively. The results obtained from this survey show that regions with low line density of highways and regions extracted as targeted sections of division roads generally agree with those regions where activities such as road and urban area maintenance are not in practice. In these regions the necessity of new road and urban city planning should be carefully considered. New projects to redevelop urban areas should take priority.

The results of this survey show:
1) GIS data was unified at about the 2500 level.
2) Various basic information was maintained as GIS data and saved.
3) Arc Info8.1 overlay function was analyzed leading to a rapid survey.

Acknowledgements

This survey was conducted under Kobe city's Planning department's fiduciary office(Kobe city urban redevelopment policy survey service), and this report was prepared from the survey carried out by Pasco Corporation. I would like to extend my gratitude to Kobe city's Planning department and its authorities for their advice and for use of their facilities.

Supplementary notes

Based on the city redevelopment law in1985, Hyogo prefecture has put forward a basic city redevelopment plan where the various measures relating to systematic urban area redevelopment are viewed from a long-term, integrated perspective.

Kazuhisa Matsunaga
PASCO CORPORATION