Changing rate of urban creep and urban expansion over time and its impact upon the hydrologic response of a catchment

Most previous quantitative research conducted on urban creep and urban expansion has focused on small areas, short time periods, case studies with fairly uniform housing stock and demographic makeup, and the characterisation of urban creep and expansion exclusively in terms of impervious area changes without quantification of the consequential hydrological impact, i.e., increase in surface runoff volume and peak flows in a catchment. This study, using satellite imagery, catchment characteristics data, geographic information system and hydrologic modelling, presents, for the first time, a long-term analysis of urban creep and expansion. The case study is the Ouseburn catchment in Newcastle upon Tyne, a wide-ranging catchment made up of rural, suburban and urban areas, over a period of seven decades. The rate of increase of impervious surfaces is found not to be constant in time; the significant impact of this variation on the catchment's hydrologic response is quantified. This has overall caused a substantial flow volume increase in the Ouseburn over the study period, e.g. 48% for a 1 in 5 years rainfall event. The conclusions obtained are likely representative of many large towns and cities across the United Kingdom and the methodology presented can be easily replicated in other study areas.

Assess the impacts of climate change on the patterns of rainfall, temperature, and streamflow in the Abelti Watershed of Southwestern Ethiopia

Changes in rainfall, temperature and streamflow (stf) will be one of the most critical factors determining the overall impact of climate change (CC). Thus, in this study we evaluated rainfall(rf), temperature, and stf pattern under changing climate in the Abelti-Watershed (a sub-watershed of upper Omo Gibe basin), Ethiopia. The Representative Concentration Pathway (RCP) scenarios of Hadley Global Environment Model 2-Earth System (HadGEM2-ES) under Coordinated Regional Climate Downscaling Experiment (CORDEX)-Africa database selected for the near (2011-2040), med (2041-2070), and end (2071-2100) periods. Hydrologic Engineering Centers-Hydrologic Modelling System (HEC-HMS) model applied for stf projection. XL-STAT conducts average annual and seasonal rf, minimum and maximum temperature (tmin&tmax), and stf trend tests. Mean seasonal and annual rf and stf variation evaluation taken using the coefficient of variation (CV). Finally, the impact of CC analysis is taken based on the baseline period. The results revealed that the climate model projection is successful for given weather stations. HEC-HMS model showed a satisfactory performance during calibration (R2=0.82) and validation (R2=0.78). The MK trend of tmin&tmax show significantly increasing; whereas rf and stf show insignificantly decreasing except under RCP8.5. The rf and stf CV analysis indicated less, moderate, and high in the study area. And the future long year average annual rf increased by -3.6%, -1.9% and -7.7%; temperature +1.15%, +2.2% and +4.2%; and stf -2.9%, -0.05% and -8.5% under RCP2.6, RCP4.5 and RCP8.5 respectively. Thus, the decrement in rf and the increment in temperature lead to more evapotranspiration and affect the stf negatively. In conclusion, stf in the Abelti-watershed could significantly decline with adverse consequences for water supplies, agriculture, and ecosystem health for the future. Therefore, this study may contribute to the planning and implementation of sustainable resources development and management strategies and help to mitigate the consequences of CC.

RavenR v2.1.4: an open source R package to support flexible hydrologic modelling

In recent decades, advances in the flexibility and complexity of hydrologic models has enhanced their utility in scientific studies and practice alike. However, the increasing complexity of these tools leads to a number of challenges, including steep learning curves for new users and in the reproducibility of modelling studies. Here, we present the RavenR package, an R package that leverages the power of scripting to both enhance the usability of the Raven hydrologic modelling framework and provide complimentary analyses that are useful for modellers. The RavenR package contains functions that may be useful in each step of the model-building process, particularly for preparing input files and analyzing model outputs, and these tools may be useful even for non-Raven users. The utility of the RavenR package is demonstrated with the presentation of six use cases for a model of the Liard River basin in Canada. These use cases provide examples of visually reviewing the model configuration, preparing input files for observation and forcing data, simplifying the model discretization, performing reality checks on the model output, and evaluating the performance of the model. All of the use cases are fully reproducible, with additional reproducible examples of RavenR functions included with the package distribution itself. It is anticipated that the RavenR package will continue to evolve with the Raven project, and will provide a useful tool to new and experienced users of Raven alike.

Calibration and Validation of HEC-HMS Model for Chalakudy River Basin

Prediction of flood prone areas in a basin and evolution of the impact of climate change on water resources needs a correct estimation of the availability of water which will solely be achieved by hydrological modelling of the basin. However, modelling the hydrology of a basin is a complex task and models should be well calibrated to increase user confidence in its predictive ability which in turn makes the application of the model effective. In this study rainfall-runoff simulation model viz., Hydrologic Modelling System, developed by the Hydrologic Engineering Centre USA (HEC-HMS) has been calibrated and validated for Chalakduy river basin in Kerala, in Sothern India for prediction of its hydrologic response. The result shows Curve Number (CN), Lag time and initial abstraction (Ia) to be the sensitive parameters for the simulated stream flow. The statistical analysis of Nash-Sutcliffe model efficiency criteria, the percentage error in peak, percentage error in volume, and net difference of observed and simulated time to peak, which were used for performance evaluation, have been found to range from (0.70 to 0.87), (4.39 to 19.47%), (1.9 to 19%) and (0 to 1day) respectively, indicating a very good performance of the model for simulation of stream flow.

Generating and analyzing Terrain characteristics from Shuttle Radar Topographic Mission (SRTM), DEM

Terrain analysis is the quantitative analysis of topographic surfaces. The purpose of a digital terrain system is to provide the digital representation of terrain so that environmental problem like soil erosion may be approached accurately and efficiently through automated means. Traditionally this was (and still is!) being done manually by using topographic/contour maps. With the availability of Digital Elevation Models (DEM) and GIS tools, watershed properties can be extracted by using automated procedures. Remote Sensing and Digital elevation models (DEMs) are known to be very useful data sources for the automated delineation of flow paths, sub watersheds and flow networks for hydrologic modelling and watershed characterization. The digital terrain model was extracted from a 90m resolution Shuttle Radar Topographic Mission (SRTM) of the study area. The SRTM data was corrected by removing voids, striping, tree offsets and random noise. The SRTM DEM data was projected from geographic coordinate WGS 84 to UTM zone 32 of the study area. The 3-D analysis tool of the ArcGIS 10.1 was used for this process. The DEM was processed to obtain the Slope, Contour, Flow direction, Flow accumulation, Flow length, Stream power Index of the study area. The study proved that SRTM elevation dataset has the ability to obviate the lack of terrain data for hydrologic modelling using ArcGIS where appropriate data for terrain modelling and simulation of hydrological processes is unavailable.

Investigation of Appropriate Model Structures for Modelling Small Urban Catchments

Although the hydrologic modelling of small urban catchments has been practised for several decades, guidance on the development of models is still needed. This research evaluates and compares several modelling structures of small residential areas with and without low impact development implementation using distributed and lumped models. Hypothetical small areas were modelled to examine several grid based models with different grid sizes. The results were used to test the ability of uncalibrated models to predict runoff using three model configurations: 1) single catchment, 2) grid, and 3) homogenous areas, where every building, backyard, and street was modelled separately as a single catchment. The results of the models were compared and evaluated based on the total runoff volume, peak flow rate, and infiltration volume. The results of a real case study show that the grid model is an appropriate model structure for modelling small urban catchments.

Investigation of Appropriate Model Structures for Modelling Small Urban Catchments

Although the hydrologic modelling of small urban catchments has been practised for several decades, guidance on the development of models is still needed. This research evaluates and compares several modelling structures of small residential areas with and without low impact development implementation using distributed and lumped models. Hypothetical small areas were modelled to examine several grid based models with different grid sizes. The results were used to test the ability of uncalibrated models to predict runoff using three model configurations: 1) single catchment, 2) grid, and 3) homogenous areas, where every building, backyard, and street was modelled separately as a single catchment. The results of the models were compared and evaluated based on the total runoff volume, peak flow rate, and infiltration volume. The results of a real case study show that the grid model is an appropriate model structure for modelling small urban catchments.

Hydrologic Modelling of Construction Site Sediment Control Pond Using SWMM

Construction activities have been identified as one of the major sources of pollution to receiving waters. Although Erosion and Sediment Control (ESC) measures reduce the amount of sediment exported from construction sites, there are still significant concerns regarding the sufficiency of current control measures to protect receiving waters. This study documents the work completed to monitor and model the performance of a typical stormwater management facility used for erosion and sediment control in suburban construction site. The main objective of this study is to provide background information regarding the performance of stormwater management facilities for treating urban construction runoff prior to discharging to receiving water bodies. The RUNOFF and STORAGE TREATMENT blocks of EPA's stormwater management model (PCSWMM4.4) were used to simulate the quantity and quality of stormwater run-off from the area under construction and assess the performance of stormwater treatment facility (Ballymore Pond) located in Richmond Hill, Ontario. The performance of the construction site sediment control pond was found to be unsatisfactory due to the high outflow concentration of suspended solids. Some specific recommendations to improve its effectiveness have been made.