| From the angle of urban geomorphology, the changes of urban landform of Jinan City in different stages of the city development were studied and contracted, and particularly a research in detail on the changes of various negative landforms in the urban and suburb region with the expanding of Jinan City was made. The influence of these changes upon the urban drainage system and flood prevention in Jinan city have been discussed. Based on the research upon the topographical feature and the situations of flooding and water logging in Jinan City in the past, the areas liable to flooding and water logging were designated in this paper.Jinan City locates in piedmont plain where is the joint position between Taishan Mountain and Huabei Plain. The relief of Jinan City is higher in south and lower in north, and shows like a shallow basin opening to the east. In geomorphologic types, the terrain occupied by the urban areas can be divided into four types: low mountain and hill region; alluvial-pluvial plain; alluvial plain; and inselbergs. The negative landforms in the urban and suburbs areas include mainly natural and semi-natural valleys and gullies, lakes, depressions or low-lying lands, and springs. Upper reaches of tributaries of Xiaoqinghe river are generally in natural form, while the main channel of Xiaoqinghe river, the city moat, the Gongshanghe and many drainage gullies are semi-natural or man-made rivers and channels. Depressions or low-lying lands are distributed in the northern part of Jinan City.The development process of Jinan City can be divided into following stages: before the commercial area so-called "Shangpu" been built; from the Shangpu had been built to 1949; from 1949 to the middle of 1950's; from 1958 to the period of "Culture Revolution"; and from 1976 to now. Urban landform in Jinan City shows following changes with the expanding of the urban area:1) Geomorphologic types in urban area become more complicated. In initial stage of formation of Jinan City, the best geomorphologic position (piedmont plain) had been chosen to construct city, while as the expanding of the urban, good landform positions had gradually been fully used. Now the urban area have toexpand into the terrain where are not ideal for city construction. So the geomorphologic types occupied by urban area increased from single kind alluvial-pluvial plain) to several kinds.2) Original natural ground of suburb area has been turned into urbanized ground, which changes the nature of the surface. As former farmlands and grass slope land have been replaced by various urban constructions and streets, the percolation ratio of this kind of urban surface decreased greatly.3) In the course of urban expanding, the changes of various negative landforms within or near the city are very distinct. Great stretches of original low-lying lands and paddy fields were opened out for the construction of commercial and residential quarters; many of smaller gullies and channels were filled or leveled up and the larger channels were usually lined, narrowed or capped and became underground sewers. The whole urban drainage system has been built up.4) Because drought and over exploitation of underground water, the spring groups of Jinan City are declining day and day. However, various constructive activities such as widening of streets and construction of high buildings, as well as the increase of impermeable surface in the region of water intake of the spring groups are also important reasons led to the declination of Jinan City's spring groups. Many springs were neglected in the course of urban expanding and remaking.Changes of the urban landform altered urban hydrological process, and affected obviously drainage and flood-prevention of Jinan City:1) In the past when the ancient Jinan City was within the limits of the city moat, rivers and gullies of southern were joined with the city moat from east or west, then flowed into Xiaoqinghe river at north of the ur...
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