Open Access Original Research Article - Special Issue

Open Access Original Research Article - Special Issue

Performance Evaluation of Low Impact Development Practices Using Linear Regression

Marija Eric, James Li, Darko Joksimovic

International Journal of Environment and Climate Change, Page 78-90
DOI: 10.9734/BJECC/2015/11578

Aims: To develop a modelling methodology for evaluating the cumulative stormwater performance of Low Impact Development technologies on a watershed basis to address stormwater impacts of urban development.
Study Design: A method is presented to perform hydrological modelling on large watersheds. Hydrological modelling simulations and linear regression analyses of a small sample of randomly selected lots were performed to generate results which were extrapolated to the entire watershed.
Place and Duration of Study: Department of Civil Engineering, Ryerson University, between September 2010 and September 2012.
Methodology: Urban hydrological response units were developed by using the K-means cluster analysis procedure to group 6926 lot parcels amenable to the residential rain barrel Low Impact Development practice into clusters. Two versions of a Microsoft Excel macro were developed to run simulations for thousands of lots simultaneously before and after Low Impact Development implementation to determine the total runoff produced by all lots for both cases. The results of computer modelling all lots were compared with the results from developing calculation methods to be used after computer modelling subsets of lots. Two calculation methods based on clustering lots to form urban hydrological response units were developed.
A random sample of 5 % of all lots was then extracted from 6616 lots amenable to the porous pavement Low Impact Development. Stepwise linear regression and linear regression were performed on the random sample for each case of no Low Impact Development and with Low Impact Development. Regression equations were used to extrapolate results from the sample to the entire data set to determine the total runoff volume produced by each set of lots.
Results: Results from the cluster-based calculation methods developed as applied to residential rain barrels were unsatisfactory since they did not approximate the output values from modelling all lots using software. The alternative method applied to porous pavement Low Impact Development implementation, entailing stepwise linear regression and linear regression, produced 945,382.97 m3 and 747,380.13 m3 of total runoff respectively. These values closely approximated corresponding values generated by the modelling software of 937,088.58 m3 and 746,462.40 m3.
Conclusion: The formation of urban hydrological response units may be unnecessary for hydrological modelling Low Impact Development technologies for large watersheds. Hydrological characteristics for only a small, randomly selected subset of all lots can be used to determine total runoff volume produced by all lots in the watershed before and after Low Impact Development implementation.

Open Access Original Research Article - Special Issue

Exploratory Assessment of SUDS Feasibility in Nhieu Loc-Thi Nghe Basin, Ho Chi Minh City, Vietnam

Ho Huu Loc, M. S. Babel, Sutat Weesakul, K. N. Irvine, Pham Minh Duyen

International Journal of Environment and Climate Change, Page 91-103
DOI: 10.9734/BJECC/2015/11534

Aims: In recent decades, Ho Chi Minh City, Vietnam, frequently has been affected by local floods and inundation from heavy rainfall. Conventional flood mitigation measures such as building flood gates and upgrading sewerage systems have been implemented but problems persist. The objective of this research is to assess another approach for flood control measures, namely Sustainable Urban Drainage Systems (SUDS), with application to the Nhieu Loc - Thi Nghe Basin, located in the central part of Ho Chi Minh City.
Methodology: A combination of the Stormwater Management Model (PCSWMM) and interviews with 140 households was used to assess the efficacy and acceptability of four of the most popular SUDS: Rainwater harvesting, green roofs, urban green space and pervious pavement. Thirteen SUDS and urban build-out scenarios were simulated under 6 design storm conditions.
Results: PCSWMM results showed that inundation from intense rainfall could be reduced with proper land-use control, specifically by maintaining imperviousness at 65% or less of the surface area. With respect to SUDS performance, green roofs were best at reducing peak runoff (22% reduction), followed by pervious pavement, urban green space, and rainwater harvesting systems. Regarding environmental improvements, as represented by reduction in total suspended solids load, urban green space was best with 20% of the solids load removed compared to the base case scenario, followed by green roofs, pervious pavement, and rainwater harvesting. The household interviews revealed the majority of people preferred pervious pavement to the other SUDS options and the least preferred option was green roof technology.
Conclusion: Considering the combination of water quantity and water quality controls, it seems that green roof technology was the best performer for this area of Ho Chi Minh City, followed by urban green space, pervious pavement and rainwater harvesting. However, green roof technology also was the least favored option for the public and stakeholder acceptance will impact SUDS implementation.

Open Access Original Research Article - Special Issue

Dynamic Modeling to Assess Natural Wetlands Treatment of Wastewater in Phnom Penh, Cambodia: Towards an Eco-City Planning Tool

Chansopheaktra Sovann, Kim N. Irvine, Sthiannopkao Suthipong, Sothea Kok, Eliyan Chea

International Journal of Environment and Climate Change, Page 104-115
DOI: 10.9734/BJECC/2015/12101

Aims: A personal computer version of the Stormwater Management Model (PCSWMM) was applied to seamlessly link urban runoff, sanitary flow, pump station operations, and a natural wastewater treatment wetland in Phnom Penh, Cambodia, as a step towards developing a planning tool that could be used to explore urban development or climate change scenarios.
Study Design: PCSWMM was calibrated with measured flow and water quality data and used to estimate total phosphorus, total nitrogen, detergents, and E. coli levels at the outlet of the wastewater treatment wetland for the period May 15 to July 1, 2011.
Place and Duration of Study: Phnom Penh, Cambodia; January, 2011 to March, 2012.
Methodology: In support of model development, a limited water quality sampling program and bathymetric survey were conducted for the sewer and wetland system in both the dry and rainy seasons, 2011. Samples were analyzed for total nitrogen, total phosphorus, detergents, and E. coli. Sewer flow was measured continuously at 5 minute intervals to determine sanitary flow characteristics as input to the model and pump operation rules were determined through interviews with the pump operators and analysis of their data log books.
Results: Consistent with past studies, the sampling showed that the wetland was effective in treating municipal waste, particularly with respect to E. coli (99% reduction from sewage inputs) and detergents (86% reduction from sewage inputs). A lower treatment efficiency was observed for total phosphorus, at around 31%, while the treatment efficiency for total nitrogen was around 71%. The wetland was divided into four zones and PCSWMM was run in continuous mode for the period May 2-July 1, 2011. The mean levels of E. coli, detergents, total phosphorus, and total nitrogen estimated by the model for that time period compared favorably with sample results from the field campaign in August, 2011.
Conclusion: The naturally-occurring wetland treatment system in Phnom Penh is effective and fits well with the concepts of green infrastructure and eco-cities. PCSWMM is a useful decision-support and planning tool to explore various development and climate change scenarios in Phnom Penh.

Open Access Original Research Article - Special Issue

A Study of Urban Heat Island using “Local Climate Zones” – The Case of Singapore

Yvonne X. Y. Ng

International Journal of Environment and Climate Change, Page 116-133
DOI: 10.9734/BJECC/2015/13051

Aims: The study of urban heat islands and traditionally relies on simplistic descriptors such as “urban” and “rural”. While these descriptors may be evocative of the landscape, they are insufficient in providing information like its site properties which have direct impacts on the surface-layer climate. The newly developed “Local Climate Zones” (LCZ) characterization scheme from Oke and Stewart [1] was applied to three case study areas to provide a more objective assessment of the urban heat island (UHI) phenomenon in Singapore.
Study Design: The three step procedure of site metadata collection, definition of the thermal source area, and selection of the appropriate climate zone was followed for the three case study areas representing green space, a typical high rise residential housing area, and the CBD to identify and explain UHI characteristics.
Place and Duration of Study: Singapore; January-March, 2014.
Methodology: Characterization of the three study sites included scoring of a sky view factor, canyon aspect ratio, terrain roughness, building surface fraction, impervious surface fraction, surface energy admittance, surface albedo, and anthropogenic heat flux based on observation, photography, and Google Earth imagery, to determine the LCZ class. Temperature, wind speed, and relative humidity were recorded on an hourly basis at each site using Kestrel 4000 weather trackers and data logger at a 2 m elevation for five consecutive days in January, 2014.
Results: The three study sites were characterized as LCZ 1 (compact high rise (CBD)), LCZ 4 (open high rise (high rise residential housing area)), and LCZ 9 (sparsely built (green space)). The temperature for LCZ 9 was lower than the other two sites, with the greatest UHI intensity (difference between mean air temperature being 2.01ºC between LCZ 4 and LCZ 9. Interestingly, although the CBD area was warmer than the open high rise area between midnight and 6 a.m., a typical UHI phenomenon, the mean air temperature for the entire 5 day period was greater at the open rise site.
Conclusion: The lower temperature at the green space site emphasizes the importance of such spaces in the urban landscape as a means to make cities more liveable and resilient to climate change impacts. The higher mean temperature at the open high rise site as compared to the CBD site was related to anthropogenic activities (particularly traffic patterns), landscaping/green space, and the influence of a large green-certified building within the circle of influence at the CBD site. Overall, the use of LCZ in quantifying the UHI magnitude of Singapore was relatively straightforward to apply and this approach should be widely applied to more objectively investigate the UHI phenomenon, particularly in tropical cities.

Open Access Original Research Article - Special Issue

Modeling the Effects of Drought in Urban Economies Using Regional Input-Output Analysis

Sheree A. Pagsuyoin, Joost R. Santos

International Journal of Environment and Climate Change, Page 134-146
DOI: 10.9734/BJECC/2015/9872

Aim: This research examines the economic impacts of drought severity and duration to interdependent production sectors in an urban catchment.
Methodology: We developed a dynamic water input-output model extension to analyze the drought vulnerability and resilience of economic sectors in an urban region. The model utilizes the North American Industry Classification System (NAICS), which encompasses 65 economic sectors in our regional analysis. The model is applied to a case study of the United States (US) National Capital Region, a predominantly urban region that is considered one of the major economic drivers of the US.
Results: Simulation results identify the critical economic sectors that experience the highest inoperability and economic losses as a result of water reduction schemes implemented during drought events. In the two scenarios studied (drought warning and drought emergency), sectors exhibit disproportionate levels of resilience and sensitivity to the magnitude and duration of water reduction. In each case, the economic loss and inoperability rankings of critical sectors differ due to differences in the quantity and value of the sectors’ production outputs.
Conclusion: Observed data trends provide valuable insights for decision makers in formulating drought preparedness policies, water conservation programs, and short-term responses aimed to reduce water consumption in cases of emergency. The dynamic water reallocation I-O model developed in this study can be applied to other drought-prone regions and be used to generate insights on the economic consequences of drought, ecosystem thresholds, and water reallocation strategies that minimize the economic impacts of prolonged drought events and their ripple effects across sectors.

Open Access Original Research Article - Special Issue

Two-Dimensional Hydrodynamic Modelling of Flood Inundation for a Part of the Mekong River with TELEMAC-2D

Tung T. Vu, Phuoc K. T. Nguyen, Lloyd H. C. Chua, Adrian W. K. Law

International Journal of Environment and Climate Change, Page 162-175
DOI: 10.9734/BJECC/2015/12885

Aims: This paper presents a study on the development of a 2-dimensional (2D) hydrodynamic model based on TELEMAC-2D for the flood simulation of the river from Kratie to Kampong Cham in Cambodia, a part of the Mekong River. The motivation behind the research was to study the feasibility of TELEMAC-2D in flood forecasting, and specifically to determine its adequacy in flood simulations with a focus on the reduction in model run-time through parallelization.
Place and Duration of Study: DHI-NTU Centre, Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, between November 2013 and March 2014.
Methodology: We simulated an actual flood event which occurred between June to November in 2001 for the stretch of the Mekong River from Kratie to Kampong Cham and compared the model simulations with MODIS satellite Images for specific days in the pre-, peak- and post-flood period.
Results: It was found that during the peak-flood period, there was high percentage (> 90%) match between the simulation results and observation obtained from satellite images while the match was below 50% for the pre- and post- flood periods.
Conclusion: The 2D simulation results were consistent with observations from satellite imaging. The discrepancy at pre- and post-flood may be due to the fact that (i) the model takes into account only hydrodynamic processes of flows in the river and flood plain, it does not consider other hydrological processes such as infiltration or evaporation which may be important during the pre- and post- flood periods, and (ii) the resolution of MODIS satellite image at 500m x 500m may be too coarse and therefore not sufficient to identify flooded areas when the area is small or water depth low. Finally, it was found that the computing time can be reduced significantly with parallelization using multi-core processors, albeit with lesser advantage in speedup when the number of cores increased beyond 4.

Open Access Case Study

Flood Risk Modeling of Urbanized Estuarine Areas under Uncertainty: A Case Study for Whitesands, UK

Manousos Valyrakis, Mark Solley, Eftychia Koursari

International Journal of Environment and Climate Change, Page 147-161
DOI: 10.9734/BJECC/2015/12915

Aims: The impacts of catastrophic flooding have steadily increased over the last few decades. This work investigated the effectiveness of flood modeling, with low dimensionality models along with a wealth of soft (qualitative) and hard (quantitative) data. In the presence of very low resolution or qualitative data this approach has the potential of assessing a plethora of different scenarios with little computational cost, without compromise in prediction accuracy.
Study Design: A flood risk modeling approach was implemented for the urbanized and flood prone region of Whitesands, at the Scottish town of Dumfries. This involved collection of a wide range of data: a) topographical maps and data from field visits were used to complement existing cross-sectional data, for building the river’s geometry, b) appropriate hydrological data were employed to run the simulations, while historical information about the extent, depth and impacts of flooding were utilized for calibrating the hydraulic model, and c) a wealth of photographic data obtained during the most recent December 2013 flood, were used for the model’s validation.
Place and Duration of Study: Desk study: School of Engineering, University of Glasgow; September 2013 to May 2014. Field study: Dumfries; November 2013 to January 2014.
Methodology: The HEC-RAS 1D model has been used to represent the hydraulics of the system. Flood maps were produced considering the local topography and predicted inundation depths. Flood cost and risk takes further into account the type and value of inundated property as well as the extent and depth of flooding.
Results: The model predictions (inundation depths and flood extents presented in the flood maps) were in fairly good agreement with the observed results along the studied section of the river.
Conclusion: This study presented a flood modeling approach that utilized an appropriate range of accessible data in the absence of detailed information. As the level of performance was comparable to other inundation models the results can be used for identification of flood mitigation measures and to inform best management strategies for waterways and floodplains.

Open Access Original Research Article

Spatial and Temporal Trend of Water Resources in Beijing, China during 1999-2012 and Its Impact Analysis

Huili Gong, Tao Tang, Zhaoning Gong, Xiaojuan Li, Yuzhu Chen, Wenji Zhao

International Journal of Environment and Climate Change, Page 176-188
DOI: 10.9734/BJECC/2015/13861

Aims: The objective of this research is to understand and analyze the trend of water resources and its effects on land subsidence, vegetation cover change, and water supply reservoir drawdown in Beijing, China.
Study Design: This research combined both field monitoring data and remote sensing data to study the water resource change and its impacts in the City of Beijing, China.
Place and Duration of Study: This study water resource record data during 1999-2012 and the Landsat TM or ETM+ data in the same period to analyze the changes of water resources in the City of Beijing. The water level and water surface change of the Guanting Reservoir as a major urban water supply was analyzed since 1979 in confirmation of the trend of water resource change.
Methodology: This research applied remote sensing data analysis, GIS spatial and spatial statistical analysis, and the conventional field monitoring data of water resources to understand and visualize the trend of water resource change and its environmental impacts in Beijing, China.
Results: This research shows that both surface water and ground water resources are declining owing to the decrease of precipitation in Beijing. In the meantime, the proportion of agricultural and industrial water consumptions was gradually reduced and that of urban and domestic water consumptions continuously increased. Land subsidence spatially coincides with groundwater level decrease, and the maximum quantity could reach five meters. Vegetation cover and NDVI index showed high correlation with precipitation in mountainous region, but does not reflect the natural water supply in plain regions in Beijing. The surface water area in the Guanting Reservoir drastically reduced since 1979.
Conclusion: The trend of water resource changes indicate that the water supply shortage in Beijing area was intensified. The more effective planning of economic development and urban growth in Beijing according its water resources is needed.