Integrated Environmental Modelling Framework for Cumulative Effects Assessment

Global warming and population growth have resulted in an increase in the intensity of natural and anthropogenic stressors. Investigating the complex nature of environmental problems requires the integration of different environmental processes across major components of the environment, including water, climate, ecology, air, and land. Cumulative effects assessment (CEA) not only includes analyzing and modeling environmental changes, but also supports planning alternatives that promote environmental monitoring and management. Disjointed and narrowly focused environmental management approaches have proved dissatisfactory. The adoption of integrated modelling approaches has sparked interests in the development of frameworks which may be used to investigate the processes of individual environmental component and the ways they interact with each other. Integrated modelling systems and frameworks are often the only way to take into account the important environmental processes and interactions, relevant spatial and temporal scales, and feedback mechanisms of complex systems for CEA. This book examines the ways in which interactions and relationships between environmental components are understood, paying special attention to climate, land, water quantity and quality, and both anthropogenic and natural stressors. It reviews modelling approaches for each component and reviews existing integrated modelling systems for CEA. Finally, it proposes an integrated modelling framework and provides perspectives on future research avenues for cumulative effects assessment

Determination of extreme flood events in the Black Creek, Julington Creek, Dubin Creek, Big Davis Creek, Ortega River, and Pablo Creek sub-basins of the lower St. Johns River basin, Florida, USA

Extreme flood estimation is a continuously developing field of research. Economic and community well-being are dependent on flood risk preventative planning, which can only be successfully implemented through sound flood estimating methods. Without the execution of proper flood prevention measures, many communities remain at risk. In addition to a new extreme flood estimation methodology, this research presents a new approach to establish flood estimates. Traditionally, more than one flood estimate per return frequency storm does not exist. This research produced a set of 10-, 25-, 50-, and 100-year flood estimates for the Black Creek, Julington Creek, Durbin Creek, Big Davis Creek, Ortega River, and Pablo Creek sub-basins in northeastern Florida. The flood estimates for each recurrence interval were developed using HSPF hydrologic modeling, statistical computations involving the use of the Log-Pearson Type III and Power Law distribution, and analysis of existing Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS) estimates. Sensitivity of parameters such as land-use change, precipitation frequency values (median versus 90th percentile), and rainfall distribution (uniform versus Synthetic Type II Modified) were assessed in the resulting extreme flows determined from the HSPF Model. The hydrologic modeling component presented in this research utilizes the St. John’s River Water Management District’s (SJRWMD) powerful Hydrologic Simulation Program – FORTRAN (HSPF) model. This is a new methodology as the SJRWMD’s HSPF model has previously never been used to estimate extreme flood flows. This methodology has the capability of being implemented in any sub-basin along the St. Johns River in Florida

Evaluation of the swat model in simulating catchment hydrology : case study of the Modder river basin

Thesis (M. Tech. (Civil engineering)) - Central University of Technology, free State, 2013Hydrological models have become vital tools for understanding hydrologic processes at the catchment level. In order to use model outputs for tasks ranging from regulation to research, models should be scientifically sound, robust, and tenable. Model evaluation is therefore beneficial in the acceptance of models to support scientific research and to guide policy, regulatory, and management decision-making. The objective of this study was to evaluate the performance of the SWAT model in simulating stream flow for the Modder River Basin. The study area is situated at -29° 11’ latitude and 26° 6’ longitude at an elevation of 1335 m and drains a land area of 949 km2. The land cover is mainly grassland (pasture) with other minor land use types. The climate of the area is semi-arid with Mean Annual Precipitation (MAP) of 563 mm. Two techniques that are widely used in evaluating models, namely quantitative statistics and graphical techniques, were applied to evaluate the performance of the SWAT model. Three quantitative statistics, namely Nash-Sutcliffe efficiency (NSE), percent bias (PBIAS), and ratio of the mean square error to the standard deviation of measured data (RSR), in addition to the graphical techniques, were identified to be used in model evaluation. Results of calibration and validation of the model at a monthly time step gave NSE of 0.65, Pbias of 15 and RSR of 0.4, while NSE of 0.5, Pbias of 31 and RSR of 0.5 were recorded for validation. According to monthly model performance ratings, the model performed well during calibration and performed satisfactory during the validation stage

An Assessment Of The Use Of Green Stormwater Infrastructure For Flood Mitigation At Berry Brook

This research examined the effectiveness of GSI and other BMPs to control urban flooding for extreme precipitation events and compared the impacts of increasing impervious cover with the impacts of increasing rainfall intensity caused by climate change. The City of Dover has spent the last decade implementing best management practices in the 185-acre Berry Brook watershed to combat stream pollution and flooding caused by urbanization. Improvements to the watershed included building additional headwater wetland area, daylighting and restoring 1,100 feet of stream, and redirecting stormwater to GSIs, thereby reducing the effective impervious cover from 30% to 10%. Four PCSWMM models of the Berry Brook watershed were developed for the analysis: a pre-implementation model, a model of the pre-implementation watershed set to 15% IC, a model of the pre-implementation watershed set to 0% IC, and a model of the watershed after BMP implementation. The four models were used to examine the effects of GSI implementation, changing impervious cover, and climate change on urban watershed hydrology for the 2-year, 10-year, 50-year, and 100-year extreme precipitation events. The effectiveness of GSI and other BMPs to control urban flooding caused by extreme precipitation events was tested by comparing the peak flows, time to peak flows, runoff depth, and total storm flow volume. A long-term rainfall-runoff simulation from 2001 to 2011 was also done for the watershed with and without GSI. It was found that BMP implementation caused an median decrease in extreme peak flow of 7%, an increase in the time to peak flow of 3 minutes, a decrease in the runoff depth of 29%, and a decrease in the total storm flow volume of 30%. GSI impact was more prevalent in short duration extreme precipitation events than in long duration events. In the 10-year analysis, annual maximum flow decreased 8%. The infiltration of rainfall increased by 17% and the stormwater runoff decreased by 40%. This showed implementing GSI in an urban watershed will reduce flooding caused by extreme precipitation events but not eliminate it. For common storms of about no more than 1.3 inches, it was found that GSI reduced peak flows by a median of 68%. Increasing IC in the watershed was shown to have a much more dramatic effect than the increase in rainfall caused by climate change. Impact was still more prevalent in short duration extreme precipitation events than in long duration events. The difference between the BMP-managed watershed under future climate change conditions and the traditionally managed watershed under current day conditions was minimal, implying BMP implementation will keep flooding from getting any worse as the climate shifts, but by itself, GSI will not eliminate urban flooding

Modelling in ungauged catchments using PyTOPKAPI : a case study of Mhlanga catchment.

Masters Degree. University of KwaZulu-Natal, Durban.Hydrological modeling of rainfall-runoff processes is a powerful tool used in various water resources applications, including the simulation of water yield from ungauged catchments. Many rivers in developing countries are poorly gauged or fully ungauged. This gives rise to a challenge in the calibration and validation of hydrological models. This study investigated the applicability of PyTOPKAPI, a physically based distributed hydrological model, in simulating runoff in ungauged catchments, using the Mhlanga River as a case study. This study is the first application of the PyTOPKAPI model to simulate daily runoff on an ungauged catchment in South Africa. The PyTOPKAPI model was parameterised using globally available digital elevation data (DEM), satellite-derived land cover, soil type data and processed hydro-meteorological data collected from various sources. Historical 30-year (1980-2009) quaternary monthly streamflow (from a well-tested and calibrated model) and daily meteorological variables (rainfall, temperature, humidity and so on) were obtained. The rainfall data were subjected to double mass curve test to check for consistency. The monthly streamflow was transposed to the catchment and disaggregated to daily streamflow time step. The PyTOPKAPI model was calibrated using an average runoff ratio as an alternative to matching streamflow data that is usually used for model calibrations. The simulated results were thereafter compared with the disaggregated monthly quaternary data. The model results show good overall performance when compared with the average runoff ratio, monthly disaggregated streamflow and the expected mean annual runoff in the catchment. In general, PyTOPKAPI can be used to predict runoff response in ungauged catchments, and thus may be adopted for water resources management applications

Improvement of Low Impact Development (LID) models coupled with watershed models: Application, performance, and optimization

Department of Urban and Environmental Engineering (Environmental Science and Engineering)Urbanization has influenced the environmental and hydrological cycles in local, global and regional scales. This can cause urban flooding including sewer water overflows and spilling pollutants that pose a risk of human health. Hence, urban water sustainability and planning have drawn public attention. Low Impact Development (LID) practices have been mentioned to improve the environmental, hydrological, and social outcomes. Therefore, our study developed LID modules to optimize and simulate LID facilities. We hope that developed modeling tools will establish effective LID strategies for improving urban management and sustainability. In an urban watershed, the first flush effect (FFE) is one of the greatest issues facing the urban environment. It indicates a greater discharge of the load of the early part in the rainfall event. LIDs have been suggested as strategies for managing urban stormwater and pollution. However, these practices require various monitoring and modeling approaches to identify characteristics and purpose to LID. These could produce proper guidelines to optimize LID management. Our study conducted stormwater monitoring and modeling to select the optimal LID sizes in the urban area. The optimal LID size was determined for reducing mass first flush (MFF), which is an index to quantify FFE. The optimal LID sizes showed range of 1.2 mm to 3.0 mm in terms of runoff depths. To increase the effectiveness of LID, the optimization process is important. Hence, this study developed optimizing tool for bioretention considering hydrological watershed properties. The model could calculate soil infiltration under hydrological conditions and hydraulic structure. Using this model, we could generate an optimized plan for bioretention based on Flow Duration Curve (FDC). The optimized result demonstrated that the soil texture, location and size are important factors affecting bioretention. Previous LID models have limitations to calculate the detailed water movement. Therefore, we developed a new LID model by coupling the stormwater management model and HYDRUS-1D (SWMM-H) models to enhance simulations of hydrological processes. Rainfall-runoff monitoring was conducted for a pilot-scale green roof and urban sub-catchment. The developed LID module was evaluated with the observed data, while the hydrologic performance of the developed model was assessed by considering scenarios of green roof sizes and soil types. Soil moisture in the green roof was simulated more accurately using SWMM-H than with SWMM. The scenario analysis demonstrated that SWMM-H estimated a more reasonable soil type (sandy loam) for managing runoff than SWMM (sand). The water quality module in LID was simplified in that water quality simulation only considered the dilution effect of rainfall. This study solved this limitation by modifying the LID-water quality module in the stormwater management model (SWMM). We evaluated the modified module by simulating TSS, COD, TN, and TP for LID facilities. The developed module applied the scenarios analysis of LID under climate change conditions. The modified module produced accurate simulation for pollutant, yielding an average ratio of root mean square error (RMSE) to the observation standard deviation ratio (RSR) of 0.52, while the original module presented an unacceptable performance with an RSR value of 1.11.This scenario analysis showed that the hydrological simulation was sensitive to the volume of rainfall while the water quality simulation was sensitive to the temporal distribution of rainfall.clos

Estimation of urban imperviousness and its impacts on flashfloods in Gazipaşa, Turkey

The paper examines flooding issues under rapid urbanization in Gazipasa city during the past seven years 2013-2019. The Storm Water Management Model (SWMM) integrated with the satellite images representing temporal variation in the land use and land cover (LULC) characteristics of the city were used to determine the variation in the runoff generation capacity, flood volume, and associated risks. The Google Earth software together with GIS technology were utilized to create and handle spatial data required for SWMM simulation. Standard design storm intensity derived from the local intensity-duration-frequency curves was used as the stationary input parameter for SWMM simulation in both the past and current LULC conditions. The comparison between LULC maps showed that the extent of urban imperviousness area has been approximately increased by 80% in average. The SWMM simulations showed the peak flood value of 51.3 m3 /sec and 61.4 m³/sec for the year 2013 and 2019, respectively. Moreover, under the same design storm, Rational Method has been applied and 39 m3 /sec of peak flow rate has been calculated by disregarding the urbanization activity. The results indicate that the LULC variation during the past seven years resulted in almost 20% (18%) increase in peak flow (flood volume).No sponso

Advancing understanding of development policy impacts on transboundary river basins: Integrated watershed modelling of the Lower Mekong Basin.

The management of transboundary river basins across developing countries, such as the Lower Mekong River Basin (LMB), is frequently challenging given the development and conservation divergences of the basin countries. Driven by needs to sustain economic performance and reduce poverty, the LMB countries are embarking on significant land use changes in the form hydropower dams, to fulfill their energy requirements. This pathway could lead to irreversible changes to the ecosystem of the Mekong River, if not properly managed. This thesis aims to explore the potential effects of changes in land use —with a focus on current and projected hydropower operations— on the Lower Mekong River network streamflow and instream water quality. To achieve this aim, this thesis first examined the relationships between the basin land use/land cover attributes, and streamflow and instream water quality dynamics of the Mekong River, using total suspended solids and nitrate as proxies for water quality. Findings from this allowed framing challenges of integrated water management of transboundary river basins. These were used as criteria for selecting eWater’s Source modelling framework as a management tool that can support decision-making in the socio-ecological context of the LMB. Against a combination of predictive performance metrics and hydrologic signatures, the model’s application in the LMB was found to robustly simulate streamflow, TSS and nitrate time series. The model was then used for analysing four plausible future hydropower development scenarios, under extreme climate conditions and operational alternatives. This revealed that hydropower operations on either tributary or mainstream could result in annual and wet season flow reduction while increasing dry season flows compared to a baseline scenario. Conversely, hydropower operation on both tributary and mainstream could result in dry season flow reduction. Both instream TSS and nitrate loads were predicted to reduce under all three scenarios compared to the baseline. These effects were found to magnify under extreme climate conditions, but were less severe under improved operational alternatives. In the LMB where hydropower development is inevitable, findings from this thesis provide an enhanced understanding on the importance of operational alternatives as an effective transboundary cooperation and management pathway for balancing electricity generation and protection of riverine ecology, water and food security, and people livelihoods

Development of a distributed water quality model using advanced hydrologic simulation

Cypress Creek is an urbanizing watershed in the Gulf Coast region of Texas that contributes the largest inflow of urban runoff containing suspended solids to Lake Houston, the primary source of drinking water for the City of Houston. Historical water quality data was statistically analyzed to characterize the watershed and its pollutant sources. It was determined that the current sampling program provides limited information on the complex behaviors of pollutant sources in both dry weather and rainfall events. In order to further investigate the dynamics of pollutant export from Cypress Creek to Lake Houston, fully distributed hydrologic and water quality models were developed and employed to simulate high frequency small storms. A fully distributed hydrologic model, Vflo(TM) , was used to model streamflow during small storm events in Cypress Creek. Accurately modeling small rainfall events, which have traditionally been difficult to model, is necessary for investigation and design of watershed management since small storms occur more frequently. An assessment of the model for multiple storms shows that using radar rainfall input produces results well matched to the observed streamflow for both volume and peak streamflow. Building on the accuracy and utility of distributed hydrologic modeling, a water quality model was developed to simulate buildup, washoff, and advective transport of a conservative pollutant. Coupled with the physically based Vflo(TM) hydrologic model, the pollutant transport model was used to simulate the washoff and transport of total suspended solids for multiple small storm events in Cypress Creek Watershed. The output of this distributed buildup and washoff model was compared to storm water quality sampling in order to assess the performance of the model and to further temporally and spatially characterize the storm events. This effort was the first step towards developing a fully distributed water quality model that can be widely applied to a wide variety of watersheds. It provides the framework for future incorporation of more sophisticated pollutant dynamics and spatially explicit evaluation of best management practices and land use dynamics. This provides an important tool and decision aid for watershed and resource management and thus efficient protection of the sources waters