Technical Notes: Determination of Manning Roughness Coefficient for PVC Gutters
Abstract: This study is about
the determination of the Manning roughness coefficient for a PVC (Polyvinyl
Chloride) gutter and of its capacity due to longitudinal-slope changes. Both
the roughness coefficient and gutter slope are factors that greatly affect both
the velocity and depth of flow in a channel. For this purpose, an experiment is
performed in the laboratory using a PVC gutter with adjustable slopes. The
Manning formula, i.e. a function of: flow rate; chan-nel roughness coefficient;
flow depth (wet cross-sectional geometries); and channel longitudinal-slope, is
then used. Water is supplied by a pump, and the discharge flow rate is
determined by collecting the water that comes out at the end of the gutter
downstream using a bucket. Then, both the volume of water in the bucket and the
time it taking are measured. The flow depths are measured with a ruler (the
other geometry sizes of the gutter are fixed, the length of 4m, width 12cm,
height 10cm). These measurements were performed five times for each slope
variation with 1cm/4m step (from 1cm/4m to 10cm/4m). The results show that the
values of the Manning roughness coefficient for the PVC gutter range from 0.010
to 0.014. Due to an increase in the slope of 1cm/4m to 10cm/4m, the flow depth drops
60% to 40% for the same discharge.
Author: Mas Mera
Journal Code: jptsipilgg130003
