The objectives of the study are: 


The project’s major project achievements are the verification of Manning’s n values for bio-retention swales, calibration of required parameters for SWMM modeling, and confirmation of swale capability in flow attenuation for various rainfall events.  The results confirm the flow retarding effect of swale due to the presence of grass along its boundary.  The application of swale as one of “control-at-source” methods is established over a five-year period (2003 – 2007) during various rainfall events covering 1-yr, 2-yr, 5-yr, 10-yr and 50-yr events.




SWMM thumbnailSWMM Modeling Result


Observed Values of Manning’s n for Station A (Swale Type B)

Date Flow Depth(m) Velocity, V
Discharge, Q
Manning’s n
26.09.2006 0.40 0.078 0.059 0.137
11.11.2006 0.47 0.096 0.087 0.119
15.11.2006 0.31 0.057 0.027 0.150
08.12.2006 0.50 0.106 0.100 0.114


     GrafVariation of Manning n


test rig thumbnail       test h1 thumbnail       test g1 thumbnail
Test Rig for Sub-drainage component   Sub-drainage component   Experimental Work
TypeA thumbnail   TypeB thumbnail   Measurement thumbnail
Discharge measurement station (Site A)   Discharge measurement station (Site B)   Flow discharge measurement