Drafts by Dr. Sunny Agarwal
Urban pluvial flood are attracting growing public concern due to rising intense precipitation and... more Urban pluvial flood are attracting growing public concern due to rising intense precipitation and increasing consequences. Accurate risk assessment is critical to an efficient urban pluvial flood management, particularly in transportation sector. This paper describes an integrated methodology, which initially makes use of high resolution 2D inundation modeling and flood depth-dependent measure to evaluate the potential impact and risk of pluvial flash flood on road network in the city center of Shanghai, China. Intensity-Duration-Frequency relationships of Shanghai rainstorm and Chicago Design Storm are combined to generate ensemble rainfall scenarios. A hydrodynamic model (FloodMap-HydroInundation2D) is used to simulate overland flow and flood inundation for each scenario. Furthermore, road impact and risk assessment are respectively conducted by a new proposed algorithm and proxy. Results suggest that the flood response is a function of spatio-temporal distribution of precipitation and local characteristics (i.e. drainage and topography), and pluvial flash flood is found to lead to proportionate but nonlinear impact on intra-urban road inundation risk. The approach tested here would provide more detailed flood information for smart management of urban street network and may be applied to other big cities where road flood risk is evolving in the context of climate change and urbanization.
Growing concern on climate-related flood hazards has led to increasing interest in understanding ... more Growing concern on climate-related flood hazards has led to increasing interest in understanding the interactions between climate, flood, and human responses. This paper jointly investigates climate change trends, impacts on flood events, flood vulnerability and risk, and response strategies in the Pearl River Delta (PRD), a rapidly urbanizing coastal area in southeast China. Our analysis based on a reanalysis dataset and model projections are integrated with literature results, which indicates a climate scenario of increasing mean temperature, precipitation, sea level, typhoon intensity, and the frequency of extreme weather events in the PRD. These trends, together with the continuing urbanization in flood-prone areas, are expected to increase flood frequency and aggravate both the scale and degree of flooding in the PRD area. We further estimate the flood vulnerability of the 11 PRD cities using the indicator system method. The results suggest that the exposure and sensitivity of central cities (Hong Kong, Macao, Shenzhen, and Guangzhou) are very high because of highly exposed populations and assets located in lowland areas. However, the potential vulnerability and risk can be low due to high adaptive capacities (both by hard and soft flood-control measures). A novel framework on flood responses is proposed to identify vulnerable links and response strategies in different phases of a flood event. It further suggests that the flood risks can be mitigated by developing an integrated climate response strategy, releasing accurate early warning and action guidance, sharing flood-related information, and applying the advantages of online social network analysis.
We analyze flash flooding in small urban watersheds, with special focus on the roles of rainfall ... more We analyze flash flooding in small urban watersheds, with special focus on the roles of rainfall variability, antecedent soil moisture, and urban storm water management infrastructure in storm event hydrologic response. Our results are based on empirical analyses of high-resolution rainfall and discharge observations over Harry's Brook watershed in Princeton, New Jersey, during 2005-2006, as well as numerical experiments with the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. We focus on two subwatersheds of Harry's Brook, a 1.1 km 2 subwatershed which was developed prior to modern storm water management regulations, and a 0.5 km 2 subwatershed with an extensive network of storm water detention ponds. The watershed developed prior to modern storm water regulations is an ''end-member'' in urban flood response, exhibiting a frequency of flood peaks (with unit discharge exceeding 1 m 3 s 21 km 22 ) that is comparable to the ''flashiest'' watersheds in the conterminous U.S. Observational analyses show that variability in storm event water balance is strongly linked to peak rain rates at time intervals of less than 30 min and only weakly linked to antecedent soil moisture conditions. Peak discharge for both the 1.1 and 0.5 km 2 subwatersheds are strongly correlated with rainfall rate averaged over 1-30 min. Hydrologic modeling analyses indicate that the sensitivity of storm event hydrologic response to spatial rainfall variability decreases with storm intensity. Temporal rainfall variability is relatively more important than spatial rainfall variability in representing urban flood response, especially for extreme storm events.
Pluvial flooding in urban areas is characterized by a gradually varying inundation process caused... more Pluvial flooding in urban areas is characterized by a gradually varying inundation process caused by surcharge of the sewer manholes. Therefore urban flood models need to simulate the interaction between the sewer network and the overland flow in order to accurately predict the flood inundation extents. In this work we present a methodology for linking 2D overland flow models with the storm sewer model SWMM 5. SWMM 5 is a well-known free open-source code originally developed in 1971.
Issuing warning information to the public when rainfall exceeds given thresholds is a simple and ... more Issuing warning information to the public when rainfall exceeds given thresholds is a simple and widely-used method to minimize flood risk; however, this method lacks sophistication when compared with hydrodynamic simulation. In this study, an advanced methodology is proposed to improve the warning effectiveness of the rainfall threshold method for urban areas through deterministic-stochastic modeling, without sacrificing simplicity and efficiency. With regards to flooding mechanisms, rainfall thresholds of different durations are divided into two groups accounting for flooding caused by drainage overload and disastrous runoff, which help in grading the warning level in terms of emergency and severity when the two are observed together. A flood warning is then classified into four levels distinguished by green, yellow, orange, and red lights in ascending order of priority that indicate the required measures, from standby, flood defense, evacuation to rescue, respectively. The proposed methodology is tested according to 22 historical events in the last 10 years for 252 urbanized townships in Taiwan. The results show satisfactory accuracy in predicting the occurrence and timing of flooding, with a logical warning time series for taking progressive measures. For systems with multiple rainfall thresholds already in place, the methodology can be used to ensure better application of rainfall thresholds in urban flood warnings.
An open source subcatchment generator program was developed for the Stormwater Management Model (... more An open source subcatchment generator program was developed for the Stormwater Management Model (SWMM) to automate tedious stages in the model construction process. The generator divides the investigated area into subcatchments using a uniform computation grid and connects the grid cells together and to the underlying stormwater network. The system was tested by applying it to two small urban catchments with different fractions of impervious surfaces in Helsinki, Finland, using mostly openly available data. The simulated discharge results were compared to measured data and to results obtained from manually built models. The proposed system significantly accelerated the setup of a SWMM modelling project, as the routing between the subcatchments as well as the subcatchment slopes and flow widths were directly derived from the computation grid. Automatically generated and manually constructed SWMM models produced discharge results that differed only slightly from each other.
As a result of global climate change, urban flooding has become a global concern in recent years ... more As a result of global climate change, urban flooding has become a global concern in recent years because of its significant negative impacts on cities. To cope with the frequent occurrence of urban flooding in recent years as well as water shortages, China has started a new nationwide initiative called Sponge City intended to increase urban resilience. This study aimed to examine public perceptions of and knowledge about urban flooding and sponge city construction, as well as the public's willingness to support sponge cities through two options, which includes (1) paying a domestic water fee surcharge and (2) buying government-issued credit securities. We found that most respondents knew about urban flooding and sponge cities, and also supported sponge city construction. Residents believed that government grants and public-private partnerships (PPP) should be the main financial sources for sponge city construction. However, respondents also accepted 17% of the domestic water price as a surcharge to be used for sponge city construction. Meanwhile, the willingness to pay (WTP) for government-issued credit securities for sponge city construction was 55% of the average annual capital surplus. We also found that occupation, education, and income were the main factors affecting respondents' WTP to support sponge city initiatives. Though increasing water prices by a certain amount will be acceptable to the public, a more properly designed PPP model should be considered and promoted by the government to overcome financial insufficiencies and ensure the sustainability of the sponge city initiative. (M. Sun). significantly improved. In addition, as a result of urbanization, the increase in impervious surfaces has led to increased surface runoff, increased runoff velocity, decreased time concentration, and decreased water quality, which have caused severe hydraulic problems and increased the possibility of urban flooding during storm events . Moreover, urbanization involves converting some "natural" lands (e.g., forest and grasslands) for residential or commercial use. Diverse vegetation that existed prior to development is replaced by impervious surfaces or monoculture grasses in residential green areas that are trimmed regularly and inundated with pesticides and fertilizers . Converting natural land for residential or commercial use significantly alters the water balance and increases areas with impervious surfaces. Large areas of impervious surfaces cannot absorb, maintain, filter, or purify rainwater and cause severe urban flooding. Studies have also shown that when impervious areas reach a certain ratio, habitat and waterquality indicators rapidly decline .
Benchmarking 2D hydraulic models for urban flooding Hunter et al.
Madeira, like many mountainous volcanic islands, is susceptible to flash floods.
In the present paper, a multi objective optimization approach based in Genetic Algorithm, Design ... more In the present paper, a multi objective optimization approach based in Genetic Algorithm, Design Of Experiments and Response Surface Method strategies, is applied in order to predict the optimal CFD model parameters, allowing to model with high accuracy the 3D free surface flow of urban flood propagation retaining the total computation time (CPU-time) as short as possible. An experimental data set was used in this study as a validation means for numerical optimized models. We can say that the constraints in terms of computation time and accuracy, related to the application of 3D CFD modeling for flood propagation problems can be overcome by making an optimal choice of the advanced parameters of model.
Flooding is an accumulation of water in an area either by direct rainfall irresistible to the vol... more Flooding is an accumulation of water in an area either by direct rainfall irresistible to the volume of drainage systems or a spill of huge amount of water from water bodies beyond normal limits. It could be localized, impacting a small area or could be vast or massive, impacting very large area. Urban flooding is caused by heavy rainfall overwhelming drainage capacity. It already has large economic and social impacts. These are very likely to increase if no changes are made to the unplanned development of buildings and infrastructure and poor management of urban drainage. Urban floods are a great disturbance of daily life in the city. Urbanization in developing countries doubled from less than 25% in 1970 to more than 50% in 2006. By 2020, seven of the world's ten largest economies will be from Asia. At the same time, Asia in one of the fastest urbanization regions in the world. In 2000, 37% of its population lived in cities and the proportion is projected to reach more than 50% by 2025.Across India, in the recent times, city after city has experienced floods. Through this paper, the author reviews urban flood events within India in recent past. This paper describes why it is important to study urban floods scenarios and what the need for this study is. It highlights the types and causes of the localized flooding as well as its impact and consequences. The study concludes the infrastructure and economic losses due to these urban events.
Study region: United Kingdom (UK). Study focus: Climate change and urbanization pose significant ... more Study region: United Kingdom (UK). Study focus: Climate change and urbanization pose significant threats for flooding and water quality in urban areas. This paper reviews the evidence concerning the combined impacts of urbanisation and climate on the urban water environment of inland catchments of the United Kingdom and assesses the degree of confidence in reported directions of change and response. It also assesses the utility of the evidence for setting environmental legislation and managing the urban water environment in the future and identifies knowledge gaps that limit effective and management interventions. New hydrological insights: There is a lack of nationally research focused on the dual impacts of climate change and urbanisation on flooding and water quality in UK urban areas. This is despite there being a clear acceptance that flood risk is increasing, water quality is generally not meeting desirable levels, and that combined population and climate change projections pose a pressing challenge. The available evidence has been found to be of medium-high confidence that both pressures will result in (i) an increase in pluvial and fluvial flood risk, and (ii) further reduction in water quality caused by point source pollution and altered flow regimes. Evidence concerning urban groundwater flooding, diffuse pollution and water temperature was found to be more sparse and was ascribed a low-medium confidence that both pressures will further exacerbate existing issues. The confidence ascribed to evidence was also found to reflect the utility of current science for setting policy and urban planning. Recurring factors that limit the utility of evidence for managing the urban environment includes: (i) climate change projection uncertainty and suitability, (ii) lack of sub-daily projections for storm rainfall, (iii) the complexity of managing and modelling the urban environment, and (iv) lack of probable national-scale future urban landuse projections. Suitable climate products are increasingly being developed and their application in applied urban research is critical in the wake of a series of extreme flooding events across the UK and timely for providing state-of-the-art evidence on which to base possible future water quality legislation in a post Brexit-WFD era.
Multi-million if not multi-billion dollar decisions are being made on the basis of computer model... more Multi-million if not multi-billion dollar decisions are being made on the basis of computer modeling results. The question that is often not explored is how reliable and accurate are these results? This paper explores several issues related to modeling using distributed rainfall-runoff models as they may affect accuracy and reliability of results. Issues such as continuous simulation, design storms, temporal and spatial rainfall data density in continuous simulations, aerial corrections for modeling larger catchments and others are discussed and challenges to the modeler community are posed.
Urban flooding is significantly different from rural flooding as Urbanization leads to developed ... more Urban flooding is significantly different from rural flooding as Urbanization leads to developed catchments, which in turn increases the flood peaks by 1.8 to 8 times and flood volumes by nearly 6 times 1 . Such urban flooding is basically due to the defective and inefficient urban drainage systems, and cause damage to public and private buildings and disrupts public life. This has necessitated use of simulation studies for understanding complexities related to the urban flood management. The paper describes a feasible application of EPA SWMM simulation to a typical hydrologic unit represented by an educational campus Nanded about which relatively accurate information of physical characteristics is readily available. The drainage line and sub-catchments are defined using percentage of imperviousness and further divided according to elevation. The catchment is divided in to 98 small sub catchments, 31 conduits, with 31 junction nodes. Daily rainfall data is obtained from nearby Asarjan raingage station. Arc-GIS (10.1) used for processing DEM (Digital Elevation Model) and LULC (Land Use Land Cover) data to obtain elevation and imperviousness respectively. Topographical data such as area, width, length, etc. are also taken from Arc-GIS. The selected extreme daily event was disaggregated into hourly events using reduction formula. Thereafter, the EPA SWMM is used to simulate the response of catchment to rainfall events in which runoff, water depth profile, and outflow hydrograph are obtained. Runoff is also obtained from rational formula for comparison purpose. Parameters needed for rational method are taken from CPHEEO manual, and for obtaining design intensity a frequency analysis is carried out.
The principles of sustainable and healthy urban environment are characterized by the recognition ... more The principles of sustainable and healthy urban environment are characterized by the recognition of the pivotal role of urban dwellers activities. Based on this, this research examines the impact of human activities (anthropogenic factors) on urban flooding in Ilorin west local government area of Kwara state. Systematic random sampling techniques was used in selecting 120 respondents based on the 12 geographic units susceptible to flooding in the local government of study. One household head out of every ten (10) houses identified and located in each vulnerable area was selected and administered with a questionnaire to give a total of 120 respondents. The questionnaire was designed to specifically capture the socio-cultural attitudes of individuals, specifically ordinary citizens in the destruction of modesty and threatening of urban productivity in some parts of Ilorin city. Primary data were collected on how the inhabitants dispose their waste generation, the building pattern, major flooding incidents as well as people's attitude to environmental regulation. The result of the findings showed that that there are poor waste management practices among the residents while poor governance coupled with lack of proper environmental planning lies on the part of government. These however, make environmental sanity unachievable in the study area. The research therefore suggests that everyone must cultivate the habit of cleanliness. It is specifically imperative that the national monthly environmental sanitation exercise is enforced and sustained. It also recommends that there is need to reinvent Nigerian cities through good governance in order to achieve improved and conducive urban environment in Nigeria
Floodplains with urban areas have significant effects on inundation flows. Large-scale modelling ... more Floodplains with urban areas have significant effects on inundation flows. Large-scale modelling of such zones thus requires a special treatment to involve those effects. This paper presents a shallow-water model with porosity to account for the reduction in storage and in the exchange sections due to presence of buildings and other structures on the floodplains. The introduction of the porosity in the shallow-water equations modifies the expressions for the fluxes and source terms. Furthermore, it implies the addition of a specific source term. The equations are solved by means of a finite-volume scheme with a modified HLLC Riemann solver and upwind treatment of the source terms. The possibilities of the proposed approach are demonstrated by an application to a large-scale experiment that was part of the European IMPACT project, which represents the severe flooding of the Italian Toce valley. This demonstrates the key advantage of the method, as it allows an accurate representation of the flow without detailed meshing of the urbanized area.
India is one of the most flood-prone countries in the world after Bangladesh and these are quite ... more India is one of the most flood-prone countries in the world after Bangladesh and these are quite common throughout the country. However, their characteristics differ from region to region. Flooding behavior and their management at national level have been investigated in this article. Floods are caused mainly due to the extreme spatial and temporal variation in the quantity of rainfall and meteorological conditions during monsoon season (June-September). About 80% of the total annual rainfall is concentrated during the period, resulting in a very high discharge from rivers, causing extensive damage to life and property. The National Flood Control Program has been launched in the country in the year 1954. Since then, sizeable progress has been made in structural and non-structural flood protection measures. Structural measures involve the construction of physical structures like embankments, dams, drainage channels, and reservoirs that prevent flood waters from reaching potential damage centers, whereas non-structural measures like flood forecasting aim at improving the preparedness to floods by keeping people away from flood waters. Institutional and legal setup to mitigate the impacts of floods has evolved over the years. Nevertheless, statistics do not reveal major reduction in the flood damages. However, river-friendly and less-interventionist approaches have been suggested to achieve sustainable flood management.
Uploads
Drafts by Dr. Sunny Agarwal
evaluating the stresses on the soil and the frame structure under the guidance of SSI, the full - Structure Interaction of foundation is a model and SAP2000 software is using based on it analysed in the finite element. Finally, a comparison of reinforced concrete
framed buildings with and without SSI was conducted.
territory for authentic most extreme exceptional precipitation occasion just as future extraordinary precipitation circumstances. Flooding circumstances of future is computed by using RCP 4.5 NOAA- GFDLESM2M climate model downscaled data. Infiltration and Flow routing are the two essential aspects of SWMM. Modified Green-Ampt strategy is utilized for the penetration while Dynamic Wave technique is picked for Flow Routing. SWMM results are exhibited as diagrams, tables which helps in understanding the flood area and hubs.
Scenarios of GCM data. Results shown that there is a rapid growth in temperatures and rainfall events in future. It shows that the max average temperature of 30.5℃ during the period of (2081-2084) for RCP 8.5 at the same time RCP 2.6 is showing lesser temperature events than the other two RCP scenarios.