Subsurface perforated pipes drain infiltrated stormwater runoff while attenuating the peak flow. The Manning roughness coefficient (n) was identified as a fundamental parameter for estimating roughness in various subsurface channels. Hence, in this work, the performance of a six-row non-staggered sand-slot perforated pipe as a sample of the subsurface drainage is investigated experimentally in a laboratory flume at Universiti Sains Malaysia (USM) aimed at determining the Manning roughness coefficients (n) of the pipe and assessing the relationship between the Manning’s n and the hydraulic parameters of the simulated runoff flow under the conditions of the tailgate channel being opened fully (GFO) and partially (GPO), as well as the pipe having longitudinal slopes of 1:750 and 1:1000. Water is pumped into the flume at a maximum discharge rate of 35 L/s, and the velocity and depth of the flow are measured at nine points along the inner parts of the pipe. Based on the calculated Reynolds numbers ranging from 38,252 to 64,801 for both GFO and GPO conditions, it is determined that most of the flow in the perforated pipe is turbulent, and the calculated flow discharges and velocities from the outlets under GFO are higher than the flow and velocity rates under GPO with similar pipe slopes of 1:750 and 1:1000. The Manning coefficients are calculated at nine points along the pipe and range from 0.004 to 0.009. Based on the ranges of the calculated Manning’s n, an inverse linear relationships between the Manning coefficients and the flow velocity under GFO and GPO conditions are observed with the R2 of 0.975 and 0.966, as well as 0.819 and 0.992 resulting from predicting the values of flow velocities with the equations v = ((0.01440 − n)/0.009175), v = ((0.01330 − n)/0.00890), v = ((0.02007 − n)/0.01814), and v = ((0.01702 − n)/0.01456) with pipe slopes of 1:750 and 1:1000, respectively. It is concluded that since the roughness coefficient (Manning’s n) of the pipe increases, it is able to reduce the flow velocity in the pipe, resulting in a lower peak of flow and the ability to control the quantity of storm water in the subsurface urban drainages.
The Cameron Highlands are particularly susceptible to erosion because of their agricultural and urban expansion. Numerous existing and proposed development projects in the Cameron Highlands have contributed to this scenario which risks the environment. Thus, this study uses the USLE model with a GIS application to assess the risk of soil loss in Cameron Highlands. An earlier study by PLANMalaysia and the Department of Agriculture Malaysia, which documented varying land use and land cover, yielded different soil loss risk estimates in the Cameron Highlands. Town growth and development are reflected in land-use statistics from PLANMalaysia, whilst agricultural influence is reflected in land-use data from the Department of Agriculture. Based on the findings, REDAC USM's soil loss risk level estimated that 6.72 per cent of the Cameron Highlands have a 'HIGH' risk or higher. With the use of this new soil loss risk level developed by REDAC USM, farmers and local authorities may be able to regulate present land-use habits, reduce soil loss and erosion, and promote environmental sustainability in the Cameron Highlands.
Subsurface drainage is part of a sustainable drainage system's components. This component represents the infiltration of stormwater into the subsurface drainage system for flow attenuation purposes. This study examines the flow parameters of subsurface drainage components. The laboratory validation of perforated subsurface drains was conducted at a longitudinal slope gradient of 1/500 with the Gate Fully Open. The manning, n data obtained in these experiments varies with several hydraulic parameters. Therefore, the experimental relationship between the flow characteristics of these subsurface drain components has been investigated. The relationship between flow behavior has been determined. The sub-critical and supercritical, and turbulence flow has occurred in this study.
Water shortage has been an issue for urbanized areas. For the Penang state in Malaysia, it is forecast that there will be a significant increase in water demand in the future. Penang authorities in Malaysia are trying to find an alternative water source to overcome the problem, with one of the options being the Perai River catchment. However, the river water quality was found to be polluted and not suitable to be used for water extraction for domestic consumption. This paper aims to study the pollution level variation due to changes in rainfall during the year in the Perai River Basin, and estimate the TMDL of the river in a particular case for BOD, COD, and NH3N parameters. A water quality model was developed for the Perai River, Jarak River and Kulim River using InfoWorks ICM. The year 2016 was selected as a model event due to data availability. BOD, COD and NH3N concentrations were used for TMDL calculation, and the load duration curve approach was used to estimate TMDL. The tidal effect at the downstream of the Perai River was found to impact the data analysis in the river stretch. It was found that pollutant load exceedance was the highest during the rainy season and the problematic pollutant was NH3N. Thus, local authorities need to focus on tidal and seasonal change factors when developing action plans to manage water quality issues in this basin.
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