One of the best management practices (BMPs) for stormwater quality and quantity control is a bioretention system. The removal efficiency of different pollutants under this system is generally satisfactory, except for nitrogen which is deficient in certain bioretention systems. Nitrogen has a complex biogeochemical cycle, and thus the removal processes of nitrogen are typically slower than other pollutants. This study summarizes recent studies that have focused on nitrogen removal for urban stormwater runoff and discusses the latest advances in bioretention systems. The performance, influencing factors, and design enhancements are comprehensively reviewed in this paper. The review of current literature reveals that a bioretention system shows great promise due to its ability to remove nitrogen from stormwater runoff. Combining nitrification and denitrification zones with the addition of a carbon source and selecting different plant species promote nitrogen removal. Nevertheless, more studies on nitrogen transformations in a bioretention system and the relationships between different design factors need to be undertaken.

Land use land cover (LULC) has altered dramatically because of anthropogenic activities, particularly in places where climate change and population growth are severe. The geographic information system (GIS) and remote sensing are widely used techniques for monitoring LULC changes. This study aimed to assess the LULC changes and predict future trends in Selangor, Malaysia. The satellite images from 1991–2021 were classified to develop LULC maps using support vector machine (SVM) classification in ArcGIS. The image classification was based on six different LULC classes, i.e., (i) water, (ii) developed, (iii) barren, (iv) forest, (v) agriculture, and (vi) wetlands. The resulting LULC maps illustrated the area changes from 1991 to 2021 in different classes, where developed, barren, and water lands increased by 15.54%, 1.95%, and 0.53%, respectively. However, agricultural, forest, and wetlands decreased by 3.07%, 14.01%, and 0.94%, respectively. The cellular automata-artificial neural network (CA-ANN) technique was used to predict the LULC changes from 2031–2051. The percentage of correctness for the simulation was 82.43%, and overall kappa value was 0.72. The prediction maps from 2031–2051 illustrated decreasing trends in (i) agricultural by 3.73%, (ii) forest by 1.09%, (iii) barren by 0.21%, (iv) wetlands by 0.06%, and (v) water by 0.04% and increasing trends in (vi) developed by 5.12%. The outcomes of this study provide crucial knowledge that may help in developing future sustainable planning and management, as well as assist authorities in making informed decisions to improve environmental and ecological conditions.

For once, mangrove forests were surprisingly resistant to the forceful impacts of the Indian Ocean Tsunami of December 2004 which swept away entire villages and caused the deaths of approximately 200,000 people. It was reported that human death and loss of property were significantly reduced in areas of dense mangrove forests in southeastern India. As the importance of mangrove is gaining attention lately, numerous countries have started to replant mangroves for coastal protection. This study discusses the extensive researches that have been conducted to study the role of mangrove forests in wave energy dissipation. These include field measurements, numerical studies and laboratory experiments. The findings illustrate that mangrove species, density, forest width, forest structure, age, water depth and incident wave height are among the factors affecting the performance of mangroves in attenuating waves. Dense forest, larger forest width, bigger trunk diameter and higher wave height resulted in relatively more wave energy dissipation by mangroves.

The flow resistance of the existing modules in the bio-ecological drainage system (BIOECODS) is high and may lead to flood instead of its mitigation. As part of efforts to enhance the performance of the system, the river engineering and urban drainage research center (REDAC) module was developed. This study modelled the hydrodynamics of flow through this module using FLOW-3D and laboratory experiments for two cases of free flow without module (FFWM) and flow with a module (FWM) to understand and visualize the effects of the module. With less than 5% error between the numerical and experimental results, REDAC module altered the flow pattern and created resistance by increasing the Manning's roughness coefficient at the upstream, depth-averaged flow velocity (43.50 cm/s to about 46.50 cm/s) at the downstream and decreasing water depth (7.75-6.50 cm). These variations can be attributed to the complex nature of the module pattern with further increase across the porous openings. Therefore, the technique used herein can be applied to characterize the behavior of fluids in larger arrangments of modules and under different flow conditions without the need for expensive laboratory experiments.

Stormwater pollutants are one of the main problems causing environmental damage. The accumulated pollutants on urban impervious surfaces are carried by stormwater runoff and enter water bodies, therefore, caused ecological damage. To decrease the pollution effect of stormwater, best management practices (BMP), and low–impact development (LID) principles were introduced. Bioretention technology as one of these practices has been used to control stormwater quality. This technology stills not widely used in Malaysia. However, the design of bioretention system that used in Malaysia follows a conventional design and stills in the early stage. Therefore, this paper reviews the role of plants and their effect on bioretention performance in terms of nutrient removal. Bioretention system that vegetated with the plant was very effective on nutrient removal than without plant. In Malaysia, there is a need to develop the conventional bioretention system. Applying multispecies plant in bioretention system would be more effective on nutrient removal. However, limited studies have been conducted on the types of plant that are suggested in (MSMA). This paper recommends applying multispecies plant (mixture plants) to enhance the performance of conventional bioretention system in terms of nutrient removal.