The Impact of Providing Surface Cover on the Soil Loss and Water Discharge under the Moderate Rainfall Event

A nation’s development purely relies on the good road infrastructure which is necessary to promote the economic growth of the country. On the other side, the detrimental effects in the form of soil loss caused by its construction cannot be neglected. Roads, regardless of their small areal periphery are equally responsible to induce higher rates of erosion when compared with the agricultural lands. This study aimed to shelter the exposed soil surface once the gradients are constructed to mitigate undesirable siltation which raises water muddiness and worsens water carrying capacity of the stream channels. To cope with this issue a full scale field test was conducted on three plots which resembles the road embankments (~30°) provided with the different percentage of land covers i.e. Plot A (fully grass covered surface), Plot B (bare surface), and Plot C (50% of the grass covered surface). The soil loss examined was sandy loam. The sediment loss was observed manually at the catchment outlet of each plot whereas, the volume rate of water flow was observed in the designed bottom container. The runs were conducted for 2 hours under the simulated rainfall events of 52 mm hr-1. The impact of simulated rainfall on the soil loss was nullified by Plot A, the soil loss was severe for Plot B, and Plot C showed preeminent results in restricting soil from flowing away. Whereas, the values of water discharge were found varying for all the plots at different time intervals which are further discussed in this paper. Keywords: erosion by water, water discharge, exposed soil surface, land cover, simulated rainfal

THE BEST FIT PROBABILITY DISTRIBUTION MODEL FOR THE ESTIMATION OF EXTREME RAINFALL IN LIMBANG, SARAWAK

In Malaysia, the increment of annual rainfall patterns is causing frequent floods, mainly in Sabah and Sarawak. Limbang river basin was selected as a case study due to it was facing of high-risk flooding problem mainly during the transition of climate. This study was aimed to estimate the frequency of rainfall under various return periods and to identify the best fit model probability distribution of annual maximum rainfall based on twenty-four hours sample in Limbang. The three statistical models were used, which are Gumbel, Log-Pearson type III, and Log-Normal. Based on the goodness of fit tests, Chi-Square, Kolmogorov Smirnov test, and the Log-Normal was found to be the best fit model for the station of Panduran. The Log-Pearson type III was found to be the best-fit distribution model for the rest of the stations, which occupies almost more than 90%. The maximum values of expected rainfall were calculated using the best fit probability distributions and could be used by a design engineer in the future

A review of safety guidelines for vehicles in floodwaters

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of River Basin Management on 2019, available online at: http://www.tandfonline.com/10.1080/15715124.2019.1687487The development of guidelines for the design and analysis of street drainage systems to ensure safety of pedestrians and vehicles is an issue of fundamental importance. To prevent pedestrians and vehicles from being swept away during flooding events, the up to date guidelines are recommended in Australian Rainfall and Runoff (AR&R, 2011) report. These guidelines are based on the upper bounds on both depth and velocity; and the constant limiting velocity × depth (v·y) functions derived from the earlier works (1967–1993) associated with the stability of old-fashioned vehicles (static condition). The AR&R (2011) guideline does not include the assessment of the studies on modern vehicles (static) which were published very close or after its release (2010–2017). However, as a result of considerable modifications in the chassis design since those former investigations, several issues concerning stability of modern vehicles in floodwaters have been raised. Herein this paper ponders on both the limit functions highlighted in those earlier and recent works. Further, the reported works have highlighted that the studies performed on vehicles in the past were limited to static condition, therefore in this paper an attempt has been made to address hydrodynamic response of a non-static vehicle endangered by floodwaters. Thus, the algorithms of the hydrodynamic studies for the non-static vehicle into safe stability limits will be presented, under the consideration of few modified parameters, which involves the rolling resistance generated at vehicle tires, drag impact at vehicle’s front end and driving force caused by vehicle enginePeer ReviewedPostprint (author's final draft

Impact and Mitigation Strategies for Flash Floods Occurrence towards Vehicle Instabilities

This chapter presents a flood risk management system for vehicles at roadways, developed from extensive experimental and numerical studies on the impact of flash floods towards vehicle instabilities. The system, easily addressed as FLO-LOW, developed to contradict the assumptions that a vehicle would be able to protect the passengers from the flood impact. Herein the hydrodynamics of flows moving across these roads coupled with the conditions of a static car that would result in vehicle instabilities has been studied. In an attempt to prevent fatalities in commonly flooded areas, permanent structures are installed to warn users regarding water depth at the flooded areas. The existing flood monitoring system only focuses on water conditions in rivers or lake in order to determine risks associated with floods. Thus, there is a need for a better system to understand and quantify a mechanism to determine hydrodynamics instability of a vehicle in floodwaters. FLO-LOW enables the road users to input their vehicle information for a proper estimation of safety limits upon crossing the flood prone area. Preferably, the system enables road users to describe and quantify parameters that might cause their vehicles to become vulnerable to being washed away as they enter the flooded area

The Common Approaches of Nitrogen Removal in Bioretention System

Bioretention is considered one of the best management practices (BMPS) for managing stormwater quality and quantity. The bioretention system has proven good performance in removing total suspended solids, oil, and heavy metals. The nitrogen (N) removal efficiency of the bioretention system is insufficient, however, due to the complex forms of nitrogen. Therefore, this paper aims to review recent enhancement approaches to nitrogen (N) removal and to discuss the factors influencing bioretention efficiency. To improve bioretention efficiency, several factors should be considered when designing bioretention systems, including nitrogen concentration, climate factors, and hydrological factors. Further, soil and plant selection should be appropriate for environmental conditions. Three design improvement approaches have been reviewed. The first is the inclusion of a saturated zone (SZ), which has been used widely. The SZ is shown to have the best performance in nitrogen removal. The second approach (which is less popular) is the usage of additives in the form of a mixture with soil media or as a separated layer. This concept is intended to be applied in tropical regions with wet soil conditions and a short dry period. The third approach combines the previous two approaches (enhanced filter media and applying a SZ). This approach is more efficient and has recently attracted more attention. This study suggests that further studies on the third approach should be carried out. Applying amendment material through filter media and integrating it with SZ provides appropriate conditions to complete the nitrogen cycle. This approach is considered a promising method to enhance nitrogen removal. In general, the bioretention system offers a promising tool for improving stormwater quality

SVM-based geospatial prediction of soil erosion under static and dynamic conditioning factors

Land degradation caused by soil erosion remains an important global issue due to its adverse consequences on food security and environment. Geospatial prediction of erosion through susceptibility analysis is very crucial to sustainable watershed management. Previous susceptibility studies devoid of some crucial conditioning factors (CFs) termed dynamic CFs whose impacts on the accuracy have not been investigated. Thus, this study evaluates erosion susceptibility under the influence of both non-redundant static and dynamic CFs using support vector machine (SVM), remote sensing and GIS. The CFs considered include drainage density, lineament density, length-slope and soil erodibility as non-redundant static factors, and land surface temperature, soil moisture index, vegetation index and rainfall erosivity as the dynamic factors. The study implements four kernel tricks of SVM with sequential minimal optimization algorithm as a classifier for soil erosion susceptibility modeling. Using area under the curve (AUC) and Cohen’s kappa index (k) as the validation criteria, the results showed that polynomial function had the highest performance followed by linear and radial basis function. However, sigmoid SVM underperformed having the lowest AUC and k values coupled with higher classification errors. The CFs’ weights were implemented for the development of soil erosion susceptibility map. The map would assist planners and decision makers in optimal land-use planning, prevention of soil erosion and its related hazards leading to sustainable watershed management

Instability Criteria for Vehicles in Motion Exposed to Flood Risks

Flooded roads have somewhat become a norm to the society and among the damages that floods can pose, there are fatalities and harm caused to people. Floating debris such as vehicles, manipulated by floodwaters could potentially cause harm not only to the public safety but also towards the public and private-owned properties. In the past, research on vehicle’s instabilities have been solely dedicated to static vehicles which are normally translated as vehicles parked on road surface. A vehicle when exposed to floodwater get influenced by different hydrodynamic forces and becomes prone to different instability modes, namely sliding, floating and toppling. Outcomes on such modes are somehow recognised in the works on static vehicles, but the mechanics of a moving vehicle under such influences have not been studied. Herein the influence of floodwater flows on the vehicle attempting to cross a flooded path (partial submergence) is presented. With that regards, a non-stationary model vehicle with the scale ratio of 1:10 (Perodua Viva) was used and a series of experiments were conducted. Moreover, a new formula to estimate the incipient velocity for a moving vehicle has been introduced and the prediction accuracy of the proposed formula has been validated using experimental data. Measurements were taken including approaching velocities and water depths, through which the instability was computed