Abstract: The fluvial-aeolian interaction in semiarid areas is becoming a new hot issue of aeolian geomorphology research. In this paper, the field survey and observation were both conducted along the Xiangshui River on the western Horqin Sand Land, Inner Mongolia, China, three typical sections were selected with each having two transects. In each transect, the cross-sectional shape and flow speed were measured; meanwhile, 31 water samples were collected in total, and the sediment loads were acquired by desiccation method. The discharges are calculated according to the speed and cross-sectional area. Results show as follows: (1)The instantaneous discharge and sediment load apparently increase from south to north, because the catchment area of mobile dune fields along the river successively augments streamwise and the riverbed is composed of loose sand which is easily eroded and carried by the flowing water. (2)In summer, the discharge is larger, and the interactions between river and its banks are evident and active. The manners of interactions are fundamentally shown as follows:running water eroding upwind riverine dunes and encroaching into the river valley by lateral erosion; upwind marginal dunes burying and pressing riverbed; the running water eroding the steep downwind valley walls composed of Q3 lacustrine sediments; river eroding the river floodplain; river laterally eroding the riverbank dunes; sand dunes in the river valley burying the river way. (3)When the normal direction of downwind steep bend coincides with the local prevailing wind direction, airflow shows an obvious convergence, wind tends to speedup, thereby exerting more intensive erosion by wind and promoting the formation of groove-shaped blowouts. Consequently, this, in turn, facilitate the formation and development of the riverbank dunes, and as the concave bank is seriously eroded, and the load accumulates at the convex bank, then favorable conditions for meandering are created. (4)As the river is not only suppressed by encroaching upwind dunes, but also blocked by downwind valley walls, the development of meandering of Xiangshui River is well-developed, but not perfect without standard loops. Therefore, the river is not a free meandering, but a confined one.

Key words: Xiangshui River, aeolian-fluvial interactions, lateral erosion, mobile dunefields, catchment effect