Research Publications

Now showing 1 - 2 of 2

Open Access
Feasibility of Sediment Budgeting in an Urban Catchment with the Incorporation of an HEC—HMS Erosion Model: A Case Study from Sri Lanka
(Springer, 2024-09-16) Abeysiriwardana, H. D.; Pattiyage, I. A. Gomes
This study aimed at studying the feasibility of using a sediment model built in HEC – HMS incorporating Modified Universal Soil Loss Equation (MUSLE) in aiding the separation of sediment contribution as point and non-point, an important aspect in sediment pollution control. The model was developed and verified using a representative sub-catchment and a canal reach of a tropical climate. The field observations and model developed had a good agreement and indicated about 16% and 35% of total sediments in the canal may be from nonpoint sources for the dry and wet seasons, respectively. Results suggested that a major fraction of eroded sediment ended up in the main canal through the dense drainage network across the catchment. This meant sediment trapping should focus tributary drainage ditches or at point source inputs to canal rather than the main canal banks. The study recognized that HEC – HMS is also capable of simulating sediment generation with acceptable errors. Being a free software package, HEC – HMS would be an effective sediment modelling tool for jurisdictions where sediment analysis has been constrained by cost.
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Deflectors to introduce heterogeneity to canals
(Faculty of Graduate Studies and Research, 2017-01-26) Gomes, P.I.A.; Kumara, G. H. V. S.; Wijethilaka, M. A. D. K.; Randima, W. A. H.
Canals are manmade lotic water systems constructed for flood control, navigation, irrigation, etc. In general, canals are eco-hydrologically homogeneous. As such, a canal might have the same prismatic cross section and an even bed profile along its course. Such characteristics do not support rich biota, something a sustainable society expects. Several past studies have attributed heterogeneity to be an important factor for a healthy stream. In this study the deflectors were used to introduce the heterogeneity in canals. In tandem studying flow complexity by deflectors, their role with respect to sediment (sand) and seed transport, and fisheries were also studied. The model canal's (laboratory flume) homogenous velocity of 0.4 m/s changed to a range of values from 0.1 to 0.7 m/s after placing deflectors. Similarly, water depth changed from a uniform 30 mm to a range from 20 mm to 70 mm. This resulted in formation of flow patches similar to flow patches formed by meso-scale physical habitats such as pools and riffles. Sediment deposition was patchy and seemed to be stable as only a minor bedload movement was observed for prolonged durations. This meant it is possible to achieve a quasi-equilibrium state in field canals where upstream brings sediments. Seed trapping was weak for floating type seeds, whereas non-floating seeds managed to get deposited with sediment. Fishes quickly migrated to the pool like areas that resulted from deflectors. The results suggested the role of deflectors in transforming a homogenous channel to heterogeneous channel that has the potential to have rich biota which is essential in ecological rehabilitation works.

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