The valley of the mid-stream in the Hsintienchi is characterized by the three curved and three straight reaches, which are disposing in alternation. The latter translate perpendicularly the terrains of northern Taiwen, and the former are in a parallel direction with strike of terrains. According to the height of river bed and the gravel, the terraces of mid-stream Hsintienchi are divided into three: upper, middle and lower. Most of the terraces are located at meander (curved) reache's. Therefore, the meanders and terraces come to be the most important problem in the Hsintienchi.
Analyzing gravels of terraces, we note Three points: (1) The exact flowage of past stream can be sure by the direction of maximum surf ace CAB plat), over 32mm, of terraces gravels. (2)The value of roundness doesn't increase with the distance when it reaches a certain extent (generally being 6). But the roundness of shale gravel is larger than either of sandstone and quartz-sandstones gravel. It' doesn't make much difference between the size of gravel and the roundness in upper terraces But in the middle and lower terraces the reverse is not just as true. (3) In shape the gravel is divided into two: called sphericity and platness. The sphericity's value of sandstone gravel of upper terraces is great, and so is the platness, value of shale stone gravel in lower terraces.
After analyzing gravel and sand of river bed, we know that the change of gravel in channel is just as in terraces; that in the upper part of Kweishan, three-quarter of gravels are shale stone and the other are sandstone. On the contrary, the gravel of sandstone and shale stone on the down part of Kweishan is almost equal in proportion. And we also note that the value of sphericity and platness of the gravels at river bed is almost as terraces', and the relationship of their value is Y=8-0.43x and r=0.88.
