The relationship between the fluvial morphology and the variation of stream power in Taiwan

Steep terrain, fragile geology and abundant rainfall result in a high sediment concentration and significant discharge variation in Taiwan rivers, which cause the unique river patterns in different regions. In this study, twenty-six main rivers in Taiwan are taken as the analytical samples, whose corresponding relationships between the total stream power and specific stream power are used to describe the morphology of different rivers and the characteristics of sediment transport. The common methods for estimating flow intensity include velocity, shear stress, and stream power. Among them, stream power is the most suitable for estimating the change in river morphology at basin scales. Therefore, stream power is used to investigate the characteristics of Taiwan rivers. Google Street View and Google Earth are used to find out the place where riparian vegetation is slightly affected by floods. Furthermore, using the Digital Elevation Model (DEM), the flow data of rivers and hydraulic geometry relations are analyzed to get its stream power characteristics. Through the analysis of these reaches, the specific stream power of which is about 20~30 W/m². These low values indicate that riparian vegetation resistant large floods and protect river banks. The study also demonstrates that the value of specific stream power can be used to discriminate the river morphology. The specific stream power is typical > 600 W/m² for mountain rivers, 100~600 W/m², for braided rivers, and < 100 W/m² for rivers in the lowland plains. The results of riparian vegetation distribution can be used as a reference for river health. Moreover, the value and variation of total stream power and specific stream power can be used to describe the developing tendency of river morphology. This is helpful to qualitatively distinguish the corresponding river morphology and the geometric property of the river.

Keywords: Stream power, Specific stream power, Riparian vegetation, River morphology, Sediment load