HKDSE Geography/M2a/Fluvial Morphometry
Fluvial morphometry describes what rivers are shaped like. You don't have to know the word - it's just that a title was needed for this section.
The stream order is counted from streams flowing from the source.
- When two first-order streams meet, they form a second-order stream.
- When two third-order streams meet, a fourth-order stream is formed.
- When a second-order stream meets a third-order stream, a fourth-order stream is formed.
This may appear in map-reading questions.
A drainage pattern is the 'shape' of the river system. Usually, it suffices to be able to identify each. The formation of each pattern is included, just in case.
|Dendritic||Looks like tree branches; tributaries join at acute angles||Uniform rock structure (same type/resistance)|
|Rectangular||Tributaries join at right angles (streams are not located at valleys)||Lines of weakness intersecting at right angles (perpendicular joint sets)|
|Trellis||Tributaries join the main stream at right angles (streams are located at valleys)||175px||Alternate layers of resistant and non-resistant rock (soft rocks are eroded to form valleys and thus tributaries)|
|Radial||Rivers flow in all directions from a centre down the sides of a hill||At a hill (conical/volcano)|
|Centripetal||Rivers flow from different directions towards central depression||still needs one||Inland basins|