In order to systematically investigate the effects of vegetation types and spatial patterns on hydrodynamics of overland flow

this study was conducted to explore variations of hydrodynamic elements such as depth

velocity

flow regime and roughness through conducting a series of laboratory flume simulation experiments on smooth and vegetated beds under conditions of emerged flow

seven flow discharges

two vegetation types (flexible vegetation

rigid vegetation) and three vegetation spatial patterns at a gentle slope gradient of 1.4%. The results showed that: (1) In comparison with bare plot

mean flow depth increased by 1.4 to 2.8 times than bare plot and mean velocity was reduced by 31% to 65% with vegetation cover

while the combination of flexible vegetation and a banded pattern retarded overland flow best. (2) Flow index m indicated that the flow with rigid vegetation and checkerboard pattern had the roughest turbulence and index k

suggesting that the combination of rigid vegetation and the pattern of a single long strip parallel to slope direction exerted the most efficient influence on flow characteristics. (3) The flow regime was mainly transition state and was majorly controlled by the discharge. With the cover of vegetation

the flow pattern changed from supercritical flow to subcritical flow and was mainly influenced by vegetation patterns. (4) Mean friction coefficient (f) of the whole slope for vegetation treatment was 2.9 to 20.9 times higher than that of bare slope

demonstrating that f increased more efficiently under subcritical flow. Emerged flexible vegetation with a banded pattern or a checkerboard pattern performed in a more efficient way than other vegetation distributions. While f alone slope distance under the banded pattern fluctuated

but the parameter kept stable with the checkerboard pattern under a better hydrodynamic condition.