Influence of Two-line Emergent Floodplain Vegetation on a Straight Compound Channel Flow

Abstract: Floods are frequent events occur in Malaysia and cause loss of life, human suffering and widespread damages to buildings, crops and infrastructure. Effort to understanding on this phenomenon is an interesting research. The objectives of this study are to determine the stage-discharge relationship, roughness coefficient and streamwise velocity distribution in a vegetated straight compound channel. The effects of two-line emergent vegetation along the edge of floodplain are studied by using a flume in the Hydraulics Laboratory, Faculty of Civil Engineering, Universiti Teknologi Malaysia (UTM). The results on stage-discharge relationship, Manning’s n and velocity distribution for overbank flows are presented in this paper. From the analysis, it is found that the vegetation influences stage-discharge where retardation of flow takes place. The maximum velocity zone is observed to be in the main channel and less fluid momentum transfer takes place in the presence of vegetation. Vegetated floodplain also influence the increases of channel roughness

Spatio-Temporal Patterns of Saltwater Intrusion in A Narrow Meandering Channel

Saltwater intrusion has become a crucial issue for water resources management across the globe. Consequently, this issue leads to problems such as encroachment on water intake zone, loss of freshwater vegetation and also disturbance to aquatic life habitat. Undeniably climate change increases the saline water flow into the river system. The meandering rivers are common, and the hydraulics is more complex than straight rivers. An experimental hydraulic investigation was carried out in the Universiti Teknologi Malaysia to elucidate the hydrodynamic interactions between saline water and freshwater in a narrow meandering channel. The spatio-temporal salinity profiles along the river are discussed in this paper. The findings prevailed a typical characteristic of a salt-wedge estuary and indicated the processes of estuarine mixing. As the saltwater flows upstream, the salinity level drops due to the dilution process. Salinity levels and densimetric Froude number were mainly driven by freshwater discharge in the channel. A variation of dilution rate in a narrow meandering channel were up to 78.9% due to strong velocity forces produced by a high freshwater discharge. Furthermore, the flow resistance induced by the channel boundaries and meander planform itself influenced the salinity intrusion profiles along the channel

Spatio-Temporal Patterns of Saltwater Intrusion in A Narrow Meandering Channel

Saltwater intrusion has become a crucial issue for water resources management across the globe. Consequently, this issue leads to problems such as encroachment on water intake zone, loss of freshwater vegetation and also disturbance to aquatic life habitat. Undeniably climate change increases the saline water flow into the river system. The meandering rivers are common, and the hydraulics is more complex than straight rivers. An experimental hydraulic investigation was carried out in the Universiti Teknologi Malaysia to elucidate the hydrodynamic interactions between saline water and freshwater in a narrow meandering channel. The spatio-temporal salinity profiles along the river are discussed in this paper. The findings prevailed a typical characteristic of a salt-wedge estuary and indicated the processes of estuarine mixing. As the saltwater flows upstream, the salinity level drops due to the dilution process. Salinity levels and densimetric Froude number were mainly driven by freshwater discharge in the channel. A variation of dilution rate in a narrow meandering channel were up to 78.9% due to strong velocity forces produced by a high freshwater discharge. Furthermore, the flow resistance induced by the channel boundaries and meander planform itself influenced the salinity intrusion profiles along the channel

Flume investigation on bed load transport and bedforms in simple channels

Massive floods hit various states in Malaysia such as Pahang, Kelantan, Johor, Terengganu, Sabah and Sarawak. It caused widespread damages to properties, infrastructures, human suffering and even deaths. More frequent floods incidents and soil erosion are reported which lead to sedimentation problems in the drainage and river systems due to urbanisation. It is important to understand the sedimentation process and the behaviour of bed forms in the water course for post-flood events. However, it is risky and dangerous to conduct field study during occurrence of flooding. Laboratory study has been chosen as an alternative to fulfill the objectives. Experimental investigations on the bed load transport and bed forms in simple channels have been undertaken. Small and large flume models are used in the laboratory. The effects of flow on mobile sandy bed channel and bed load transportation are studied by using a modified flume with an asymmetric straight compound channel. However, the findings on rate of transport and bed formation for non-flooding cases are presented in this paper. It is found that the bed formation profiles for both channels are different due to scale and flume characteristics. The bed forms, erosion and deposition processes are significantly influenced by the water velocity in the channel. The bed forms observed for large flume are repeating ripples and dunes; meanwhile variable of ripples are observed in small flume

Simulations of Depth-Averaged Streamwise Velocity of Meandering Compound Channel using TELEMAC Modules

Capabilities of numerical tools to simulate fluid problems significantly depend on its methods to solve for the Navier-Stokes equations. Different dimensional computing tools using the same horizontal meshes were used to simulate flow conditions inside non- and vegetation meandering compound channel. Both tools give good agreement for simulations of depth-averaged streamwise velocity inside the main channel, but its capabilities vary significantly for simulations on floodplains. Lower relative depth recorded a higher percentage of errors than flow with higher relative depth. Vegetation along the main channel increased the flows complexity especially in the area near the vegetation thus reducing the simulation capabilities of the computing tools. Simulations work by TELEMAC-3D significantly better in the areas with highly dimensional and turbulence conditions. TELEMAC-2D is still useful because of its simplicity and lower computing time and resources required

Simulations of Depth-Averaged Streamwise Velocity of Meandering Compound Channel using TELEMAC Modules

Capabilities of numerical tools to simulate fluid problems significantly depend on its methods to solve for the Navier-Stokes equations. Different dimensional computing tools using the same horizontal meshes were used to simulate flow conditions inside non- and vegetation meandering compound channel. Both tools give good agreement for simulations of depth-averaged streamwise velocity inside the main channel, but its capabilities vary significantly for simulations on floodplains. Lower relative depth recorded a higher percentage of errors than flow with higher relative depth. Vegetation along the main channel increased the flows complexity especially in the area near the vegetation thus reducing the simulation capabilities of the computing tools. Simulations work by TELEMAC-3D significantly better in the areas with highly dimensional and turbulence conditions. TELEMAC-2D is still useful because of its simplicity and lower computing time and resources required

Infiltrated sustainable urban drainage system for storm water control

The Best Management Practices for Sustainable Urban Drainage System including On-Site Detention have been introduced in the Storm Water Management Manual for Malaysia. Flash floods are becoming frequent in the urbanised areas in this country. Inefficient drainage system has been highlighted as one of the factors. Urban drains were reported incapable of coping with the unexpected heavy rainfall. Concrete drains are favourable in construction industry for economic reasons. An experimental research was conducted out to investigate the effectiveness of infiltration integration with drainage system to reduce flash flood. This laboratory research was conducted in the Universiti Teknologi Malaysia. Experiments were performed for selected drainage bed slopes and focussed on several spacing between precast drain sections along the system. The total and infiltrated flow rates, water surface and velocity profiles were examined. The results showed that drain flow rates were reduced by 60.9%-89.6% when the spacing between drain sections were enlarged. Meanwhile, the flow depths in drain sections were dropped by 48.2%-68.9%, and the water velocity was lowered up to 49% as the spacing between drain sections were increased. The study found that the drainage bed slope also influ­enced the performance of the infiltrated concrete drainage system

Flume scaled investigation on flood flow and bed load transport in river systems

The conference will cover areas like watershed management,flood management,water supply and water economics,coastal engineering and management