Drop
structure is a key hydraulic structure used in river improvement projects for
flood control purposes. However, as demand for riparian construction techniques
with environmental considerations is increasing both domestically and
internationally, discontinuation of aquatic organisms as a result of high head
is raised as a serious issue associated with the existing drop structures.
Accordingly, it has become necessary to install a drop structure with a mild
slope rather than the existing drop structures with high head, so that the
structure can function as a migration channel for fish, which is severed by the
existing drop structures, and also improve surrounding landscapes. In this
study, which was initiated based on the necessity as such, a drop structure of
mild slope was defined as sloping weir and flow characteristics under different
conditions were analyzed through a hydraulic experiment. Focusing on efficiency
according to energy dissipation that takes place according to different
gradients of sloping weir, particle sizes of riverbed materials and the effect
of hydraulic jump occurring at the downstream of a structure, this study aimed at
identifying flow characteristics according to the conditions of sloping weirs.
Thehydraulic experimentwas carried out on a variable-slope channel measuring 0.6 m in width and 20.0 m
in length. As for riverbed materials, materials with two particle sizes (16 mm
and 25 mm) were selected. For the experiment, models with different slope
ratios to the structure, such as 1V:2H, 1V:3H and 1V:4H, were created. For flow
conditions and hydraulic jump locations, an amount of water satisfying four
water level conditions by stage was flown according to water level at the inlet
area. Then, eight points were selected from inlet area, drop area, jet flow
area and downstream area by controlling water level at the downstream area and
adjusting the location of hydraulic jump occurrence. Water level (y), flow velocity (V), length of hydraulic jump (Lr)
and distance of hydraulic jump occurrence (Lj)
were measured at the eight points.