View All Items

Title: DEVELOPMENT OF DAILY, MONTHLY, INTER-ANNUAL, AND MEAN ANNUAL HYDROLOGICAL MODELS BASED ON A UNIFIED RUNOFF GENERATION FRAMEWORK.
Creator: Kheimi, Marwan, Wang, Dingbao, Wahl, Thomas, Singh, Arvind, Zheng, Qipeng, University of Central Florida
Abstract / Description: The main goal of this dissertation develops a unified model structure for runoff generation based on observations from a large number of catchments. Furthermore, obtaining a comprehensive understanding of the physical controlling factors that control daily, monthly, and annual water balance models. Meanwhile, applying the developed Unified model on different climate conditions, and comparing it with different well-known models.The proposed model was compared with a similar timescale model ...
Show moreThe main goal of this dissertation develops a unified model structure for runoff generation based on observations from a large number of catchments. Furthermore, obtaining a comprehensive understanding of the physical controlling factors that control daily, monthly, and annual water balance models. Meanwhile, applying the developed Unified model on different climate conditions, and comparing it with different well-known models.The proposed model was compared with a similar timescale model (HyMOD, and abcd) and applied on 92 catchments from MOPEX dataset across the United States. The HyMOD and abcd are a well-known daily and monthly hydrological model used on a variety of researchers. The differences between the new model and HyMOD, and abcd include 1) the distribution function for soil water storage capacity is different and the new distribution function leads to the SCS curve number method; and 2) the computation of evaporation is also based on the distribution function considering the spatial variability of available water evaporation. The performance of all models along with parameters used is examined to understand the controlling factors. The generated results were calibrated and validated using the Nash-Sutcliffe efficiency coefficient (NSE), indicating that the Unified model has a moderate better performance against the HyMOD at a daily time scale, and abcd model at a monthly timescale. The proposed model using the SCS-CN method shows the effect of improving the performance.
Show less
Date Issued: 2019
Identifier: CFE0007478, ucf:52684
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007478

Title: Sinkhole detection and quantification using LiDAR data.
Creator: Rajabi, Amirarsalan, Nam, Boo Hyun, Wang, Dingbao, Singh, Arvind, University of Central Florida
Abstract / Description: The state of Florida is highly prone to sinkhole incident and formation, mainly because of the soluble carbonate bedrock which is susceptible to dissolution and groundwater recharge that causes internal soil erosions. Numerous sinkholes, particularly in Central Florida, have occurred. Florida Subsidence Incident Report (FSIR) database contains verified sinkholes with Global Positioning System (GPS) information. In addition to existing detection methods such as subsurface exploration and...
Show moreThe state of Florida is highly prone to sinkhole incident and formation, mainly because of the soluble carbonate bedrock which is susceptible to dissolution and groundwater recharge that causes internal soil erosions. Numerous sinkholes, particularly in Central Florida, have occurred. Florida Subsidence Incident Report (FSIR) database contains verified sinkholes with Global Positioning System (GPS) information. In addition to existing detection methods such as subsurface exploration and geophysical methods, a remote sensing method can be an alternative and efficient means to detect and characterize sinkholes with a wide coverage. the first part of this study is aimed at developing a method to detect sinkholes in Missouri by using Light Detection and Ranging (LiDAR) data. Morphometrical parameters such as TPI (Topographic Position Index), CI (Convergence Index), SI (Slope Index), and DEM (Digital Elevation Model) have a high potential to help detect sinkholes, based on local ground conditions and study area. The GLM (General Linear Model) built in R software is used to obtain morphometrical indices of the study terrain to be trained and build a logistic regression model to detect sinkholes. In the second part of the study, a semi-automated model in ArcMap is then developed to detect sinkholes and also to estimate geometric characteristics of sinkholes (e.g. depth, length, circularity, area, and volume). This remote sensing technique has a potential to detect unreported sinkholes in rural and/or inaccessible areas.
Show less
Date Issued: 2018
Identifier: CFE0007084, ucf:51992
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007084

Title: Analysis of Hydrodynamic and Bathymetric gradients in Canaveral National Seashore following Living shoreline and oyster restorations.
Creator: Spiering, David, Kibler, Kelly, Medeiros, Stephen, Singh, Arvind, University of Central Florida
Abstract / Description: Coastal vulnerability has been gaining recognition as a critical issue, especially with the increasing predictions of sea level rise. Susceptibility to extreme events, eutrophication, and shoreline modification has left many coastal regions in a degraded state. Shoreline protection has traditionally taken the form of seawalls and offshore breakwaters which can be detrimental to both the local ecosystems and adjoining shorelines. The objective of this thesis is to analyze the hydrodynamic and...
Show moreCoastal vulnerability has been gaining recognition as a critical issue, especially with the increasing predictions of sea level rise. Susceptibility to extreme events, eutrophication, and shoreline modification has left many coastal regions in a degraded state. Shoreline protection has traditionally taken the form of seawalls and offshore breakwaters which can be detrimental to both the local ecosystems and adjoining shorelines. The objective of this thesis is to analyze the hydrodynamic and bathymetric variation that occurs within Mosquito Lagoon, Florida following living shoreline and oyster reef restorations. The shoreline sites were sampled using a Before-After-Control-Impact (BACI) design and data were analyzed to ascertain the hydrodynamic and bathymetric variations that occurred resulting from plantings of emergent vegetation and deployment of biogenic wave break structures. Turbulent statistics were calculated to determine the effects of nearshore emergent vegetation on the incoming currents and waves. The vegetative growth in conjunction with the wave break structure was shown to reduce the onshore velocities to 46% of those observed at the reference site. Surveys among restored and degraded shorelines and oyster reefs exhibit average crest heights 10-20 cm lower in the restored sites. Nearshore slopes at the hard armored TM Seawall site were over 161% steeper than the restored sites comprised of emergent vegetation and wave break structures implying that scour was present at the toe of the structure from potentially reflected wave energies and increased swash velocities. Quantifying the hydrodynamic and geomorphic processes at work within restored shorelines and reefs may aide managers in best practices both in selection of viable restoration sites and with proper implementation of restoration techniques.
Show less
Date Issued: 2019
Identifier: CFE0007535, ucf:52601
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007535

Title: Ichetucknee Springs: Measuring the Effects of Visitors on Water Quality Parameters through Continuous Monitoring.
Creator: Faraji, Sarah, Singh, Arvind, Wang, Dingbao, Mayo, Talea, University of Central Florida
Abstract / Description: Ichetucknee Springs System is in north central Florida, under the jurisdiction of the Suwannee River Water Management District (SRWMD). The Ichetucknee River is one of the most pristine spring-fed rivers in Florida and became a state park in 1970. Over 400,000 people visited the Ichetucknee Springs State Park in 2016. From that total, over 130,000 people came during the tubing season alone (Memorial Day to Labor Day). During the tubing season, only 750 visitors per day are allowed to launch...
Show moreIchetucknee Springs System is in north central Florida, under the jurisdiction of the Suwannee River Water Management District (SRWMD). The Ichetucknee River is one of the most pristine spring-fed rivers in Florida and became a state park in 1970. Over 400,000 people visited the Ichetucknee Springs State Park in 2016. From that total, over 130,000 people came during the tubing season alone (Memorial Day to Labor Day). During the tubing season, only 750 visitors per day are allowed to launch from the North Launch, near the Ichetucknee Head Spring. The park enforces visitor usage of the river during these time frames to protect the integrity of the aquatic vegetation and aquatic organisms in the northern portion of the River. The objective of this study is to evaluate the response of water quality from the Head Spring to the seasonal changes in visitor numbers to the Park. Water quality parameters were continuously monitored and recorded by a SRWMD station using a YSI EXO2 and SUNA nitrate sensor: temperature, turbidity, pH, specific conductivity, dissolved oxygen content, and nitrates (NO2+NO3). Water quality data from April 2015 to September 2017 was reviewed and processed into max daily values that were compared to daily visitor counts. Results from the statistical analysis indicate there is a significant difference in turbidity from the Head Spring during the tubing season and outside the tubing season (Kruskal-Wallis, p(<)0.001), which results from higher visitor counts during the weekends of the tubing season. However, due to inconsistency of water quality readings and equipment damage, some data were lost or outside the range of monitoring capabilities; which may have resulted in decreased correlation between water quality and daily visitor counts. Continued evaluation of water quality by continuous monitoring is warranted as it can assist the SRWMD and Ichetucknee Springs State Park Staff better monitor and evaluate the health of the Ichetucknee Springs System.
Show less
Date Issued: 2017
Identifier: CFE0006873, ucf:51748
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006873

Title: Effects of climate change and anthropogenic activities on the Everglades landscape.
Creator: Sandhu, Daljit, Singh, Arvind, Wang, Dingbao, Medeiros, Stephen, University of Central Florida
Abstract / Description: The Everglades has been experiencing major changes, both climatic and anthropogenic, such that the landscape is experiencing additional stresses and forcings leading it away from its natural equilibrium. The land within and surrounding the Everglades has undergone severe modifications that may have detrimental effects on wildlife and natural features, such as rivers and landscape connectivity. Here in this study, the main focus is on understanding and quantifying hydrologic and geomorphic...
Show moreThe Everglades has been experiencing major changes, both climatic and anthropogenic, such that the landscape is experiencing additional stresses and forcings leading it away from its natural equilibrium. The land within and surrounding the Everglades has undergone severe modifications that may have detrimental effects on wildlife and natural features, such as rivers and landscape connectivity. Here in this study, the main focus is on understanding and quantifying hydrologic and geomorphic signatures of climatic and anthropogenic changes on the Everglades landscape. For this, in particular, available data on natural hydrological processes was used, such as rainfall, groundwater elevation, streamflow as well as surface elevations and satellite images for three different regions. These regions are categorized as forested, urban (nearby Everglades regions) and transition (in between forested and urban regions). The results show distinct differences in the statistics of observed hydrologic variables for the three different regions. For example, the probability distribution functions (PDFs) of groundwater elevation for the case of urban region show a shift in mean as well as lower asymmetry as compared to forested regions. In addition, a significant difference in the slopes between smaller and larger scales of the power spectral densities (PSDs) is observed when transitioning from forested to urban. For the case of the streamflow PDFs and PSDs, the opposite trends are observed. Basin properties extracted from digital elevation models (DEMs) of the Everglades reveal that drainage densities increase when moving from the urban to the forested sub-regions, highlighting the topographic and land use/land cover changes that the Everglades has been subjected to in recent years. Finally, computing the interarrival times of extreme ((>)95th percentile) events that suggest power-law behavior, the changes in power-law exponents of the hydrologic processes further highlights how these processes differ spatially and how the landscape has to respond to these changes. Quantifying these observed changes will help develop a better understanding of the Everglades and other wetlands ecosystems for management to future changes and restoration.
Show less
Date Issued: 2016
Identifier: CFE0006495, ucf:51395
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006495

Title: Remote Sensing of Coastal Wetlands: Long term vegetation stress assessment and data enhancement technique.
Creator: Tahsin, Subrina, Medeiros, Stephen, Singh, Arvind, Mayo, Talea, University of Central Florida
Abstract / Description: Apalachicola Bay in the Florida panhandle is home to a rich variety of salt water and freshwater wetlands but unfortunately is also subject to a wide range of hydrologic extreme events. Extreme hydrologic events such as hurricanes and droughts continuously threaten the area. The impact of hurricane and drought on both fresh and salt water wetlands was investigated over the time period from 2000 to 2015 in Apalachicola Bay using spatio-temporal changes in the Landsat based NDVI. Results...
Show moreApalachicola Bay in the Florida panhandle is home to a rich variety of salt water and freshwater wetlands but unfortunately is also subject to a wide range of hydrologic extreme events. Extreme hydrologic events such as hurricanes and droughts continuously threaten the area. The impact of hurricane and drought on both fresh and salt water wetlands was investigated over the time period from 2000 to 2015 in Apalachicola Bay using spatio-temporal changes in the Landsat based NDVI. Results indicate that salt water wetlands were more resilient than fresh water wetlands. Results also suggest that in response to hurricanes, the coastal wetlands took almost a year to recover while recovery following a drought period was observed after only a month. This analysis was successful and provided excellent insights into coastal wetland health. Such long term study is heavily dependent on optical sensor that is subject to data loss due to cloud coverage. Therefore, a novel method is proposed and demonstrated to recover the information contaminated by cloud. Cloud contamination is a hindrance to long-term environmental assessment using information derived from satellite imagery that retrieve data from visible and infrared spectral ranges. Normalized Difference Vegetation Index (NDVI) is a widely used index to monitor vegetation and land use change. NDVI can be retrieved from publicly available data repositories of optical sensors such as Landsat, Moderate Resolution Imaging Spectro-radiometer (MODIS) and several commercial satellites. Landsat has an ongoing high resolution NDVI record starting from 1984. Unfortunately, the time series NDVI data suffers from the cloud contamination issue. Though simple to complex computational methods for data interpolation have been applied to recover cloudy data, all the techniques are subject to many limitations. In this paper, a novel Optical Cloud Pixel Recovery (OCPR) method is proposed to repair cloudy pixels from the time-space-spectrum continuum with the aid of a machine learning tool, namely random forest (RF) trained and tested utilizing multi-parameter hydrologic data. The RF based OCPR model was compared with a simple linear regression (LR) based OCPR model to understand the potential of the model. A case study in Apalachicola Bay is presented to evaluate the performance of OCPR to repair cloudy NDVI reflectance for two specific dates. The RF based OCPR method achieves a root mean squared error of 0.0475 sr?1 between predicted and observed NDVI reflectance values. The LR based OCPR method achieves a root mean squared error of 0.1257 sr?1. Findings suggested that the RF based OCPR method is effective to repair cloudy values and provide continuous and quantitatively reliable imagery for further analysis in environmental applications.
Show less
Date Issued: 2016
Identifier: CFE0006546, ucf:51331
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006546

Title: Implications of groundwater plume transport and analysis of karst aquifer characteristics in central Florida.
Creator: Sandhu, Daljit, Singh, Arvind, Wang, Dingbao, Nam, Boo Hyun, Zheng, Qipeng, University of Central Florida
Abstract / Description: Groundwater aquifers make up the primary source of drinking water in Florida. It is imperative to protect and maintain water quality to ensure optimal drinking water conditions. Florida is known for being prone to sinkholes due to karst features. One sinkhole event occurred beneath a phosphogypsum stack, and leaked a large amount of radioactive waste in the Floridan aquifer, raising water quality concerns. To study the behavior of contaminant transport, the radioactive waste plume was modeled...
Show moreGroundwater aquifers make up the primary source of drinking water in Florida. It is imperative to protect and maintain water quality to ensure optimal drinking water conditions. Florida is known for being prone to sinkholes due to karst features. One sinkhole event occurred beneath a phosphogypsum stack, and leaked a large amount of radioactive waste in the Floridan aquifer, raising water quality concerns. To study the behavior of contaminant transport, the radioactive waste plume was modeled by coupling hydraulic and chemistry concepts. Adsorption was studied to see if it can serve as a potential remediation solution to the contaminant waste, using available adsorption knowledge and data from previous studies. Results suggest that simulating mineral adsorption helped limit how far the waste stack would travel in the aquifer, however it would still pose risk in water quality, as drinking water wells are situated along the path of the contaminant plume. Implementation of treatment wells and monitoring would ensure drinking water criteria are met.Acknowledging that the Floridan aquifer contains karst features that consist of limestone fractures and the rock matrix, groundwater flow patterns may be influenced over time. For instance, fractures (or conduits) can conduct larger amounts of groundwater at higher conductivities, which could have implications on groundwater/contaminant transport. To model this process, a karst evolution model utilizing hydraulic and chemistry concepts are applied in a basin in Florida. Results indicate the karst model reproduces head profiles and estimates the age of several conduits. A sensitivity analysis was conducted to investigate how karst evolution is influenced by hydraulic and chemistry parameters. Results show that fracture length has more influence on karst evolution, however other physical parameters show some influence as well.A karst conduit network was simulated for the Silver Springs springshed, based on obtained potentiometric head data. Implementing information on aquifer chemistry and fracture geometry resulted in a unique realization of a karst network. During this process, flow rates change direction, inducing backflow, which can have implications on groundwater resources. Overall, an improved understanding of karst processes can aid in better characterizing conduit flow patterns and improve water resources management.
Show less
Date Issued: 2019
Identifier: CFE0007723, ucf:52427
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007723

Title: Turbulent Flame-Vortex Dynamics of Bluff-Body Premixed Flames.
Creator: Geikie, Marissa, Ahmed, Kareem, Vasu Sumathi, Subith, Bhattacharya, Samik, Singh, Arvind, University of Central Florida
Abstract / Description: This study explores the effects of turbulence and pressure-gradient tailoring on the turbulent flame and vorticity transport mechanisms of premixed flames. A turbulent premixed flame stabilized by a bluff-body in a high-speed combustor is used for the investigation. The combustor pressure gradient is altered using a variable-geometry test section. The turbulence within the combustor is controlled using a custom-designed, supersonic variable-turbulence generator. The turbulent flame-flow field...
Show moreThis study explores the effects of turbulence and pressure-gradient tailoring on the turbulent flame and vorticity transport mechanisms of premixed flames. A turbulent premixed flame stabilized by a bluff-body in a high-speed combustor is used for the investigation. The combustor pressure gradient is altered using a variable-geometry test section. The turbulence within the combustor is controlled using a custom-designed, supersonic variable-turbulence generator. The turbulent flame-flow field is measured and characterized using simultaneous high-speed particle imaging velocimetry (PIV) and CH* chemiluminescence. The flame-vortex dynamics of the turbulent flame are analyzed using a Lagrangian tracking methodology. Lagrangian fluid elements (LFEs) are tagged on the experimental data and are tracked as they propagate across the turbulent flame. The vorticity generation and transport mechanisms are decomposed along the Lagrangian trajectories to determine their relative balance under the various pressure gradient and turbulence conditions. It is demonstrated that the turbulence and induced pressure-gradient independently affect the relative magnitudes of dilatation, baroclinic torque, and vortex stretching mechanisms. Increasing the combustor pressure gradient augments the relative magnitudes of the vorticity mechanisms; baroclinic torque exhibits the largest gain for augmented pressure gradient relative to attenuated. The turbulence causes a in a reduction of the dilatation and baroclinic torque vorticity mechanisms, meanwhile the vortex stretching increases. When the turbulence and pressure gradient are altered simultaneously, the aforementioned effects superpose. These results confirm that alteration of the test section pressure gradient can be used to augment the vorticity mechanisms independently from turbulence. Furthermore, a change in the relative balance of the combustion-induced vorticity mechanisms and turbulence energy transport occurs as a result of increasing the turbulence and pressure gradient.
Show less
Date Issued: 2018
Identifier: CFE0007180, ucf:52277
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007180

Title: Physical Hydrogeological Modeling of Florida's Sinkhole Hazard.
Creator: Perez, Adam, Nam, Boo Hyun, Wang, Dingbao, Chopra, Manoj, Singh, Arvind, An, Jin Woo, University of Central Florida
Abstract / Description: Sinkholes are one of the major geohazards in karst terrain and pose a social, economic, and environmental risk. In Florida, sinkhole-related insurance claims between 2006 and the third quarter of 2010 amounted to $1.4 billion. Approximately 20 % of the United States is underlain by karst terrain formed from the dissolution of soluble rocks and is susceptible to a sinkhole hazard. Particularly, Texas, Florida, Tennessee, Alabama, Missouri, Kentucky, and Pennsylvania are known as sinkhole...
Show moreSinkholes are one of the major geohazards in karst terrain and pose a social, economic, and environmental risk. In Florida, sinkhole-related insurance claims between 2006 and the third quarter of 2010 amounted to $1.4 billion. Approximately 20 % of the United States is underlain by karst terrain formed from the dissolution of soluble rocks and is susceptible to a sinkhole hazard. Particularly, Texas, Florida, Tennessee, Alabama, Missouri, Kentucky, and Pennsylvania are known as sinkhole states.The scope of this study is to develop a physical model to simulate sinkholes (referred to as a sinkhole simulator), which can assess the qualitative behavior of the hydrogeological mechanism of Florida's sinkhole formations. Two sinkhole simulators were developed, with the second simulator constructed to overcoming the limitations of the first. The first generation sinkhole simulator incorporated a falling head groundwater system and the sinkhole could only be observed once the ground surface was breached. The second generation sinkhole simulator incorporated a constant head groundwater system which accurately depicts field conditions and the sinkhole was able to be observed during all stages of formation within this model. In both simulators multiple hydrogeological conditions were created and water level transducers were installed at various locations within the soil profile to monitor variations in the groundwater table during the sinkhole process, this was done to investigate the soil-groundwater behavior.Findings from this study include: 1) groundwater recharge is a critical sinkhole triggering factor, 2) the groundwater table cone of depression increases as the raveled zone or void travels up through the overburden due to sinkhole formation, 3) The cover-subsidence sinkhole failure mechanism is similar to the failure mechanism present in Terzaghi's trapdoor experiment and the cover-collapse failure mechanism consists of four district components: failure planes with erosion envelope, arch dropout failure, formation of elliptical void, and slope stability failure, and 4) a strong qualitative relationship between soil strength and type of sinkhole formed (cover-subsidence or cover-collapse) was observed.
Show less
Date Issued: 2017
Identifier: CFE0006637, ucf:51247
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006637

Title: Hydrologic controls on the natural drainage networks extracted from high-resolution topographic data.
Creator: Hooshyar, Milad, Wang, Dingbao, Medeiros, Stephen, Singh, Arvind, Kibler, Kelly, Weishampel, John, University of Central Florida
Abstract / Description: Drainage networks are important geomorphologic and hydrologic features which significantly control runoff generation. Drainage networks are composed of unchannelized valleys and channels. At valley heads, flow changes from unconfined sheet flow on the hillslope to confined flow in valley. Localized confined flow dominates in valleys as a result of convergent topography with positive curvature. Channels initiate at some distance down from the valley head, and the transition from unchannelized...
Show moreDrainage networks are important geomorphologic and hydrologic features which significantly control runoff generation. Drainage networks are composed of unchannelized valleys and channels. At valley heads, flow changes from unconfined sheet flow on the hillslope to confined flow in valley. Localized confined flow dominates in valleys as a result of convergent topography with positive curvature. Channels initiate at some distance down from the valley head, and the transition from unchannelized valley to channel is referred to as the channel head. Channel heads occur at a point where fluvial transport dominates over diffusive transport.From the hydrologic perspective, channels are categorized as perennial, intermittent, and ephemeral streams based on the flow durations. Perennial streams flow for the most of the time during normal years and are maintained by groundwater discharge. Intermittent (i.e. seasonal) streams flow during certain times of the year receiving water from surface sources such as melting snow or from groundwater. Lastly, ephemeral streams flow only in direct response to precipitation without continuous surface flow. In this dissertation, the hydrologic controls on the drainage networks extracted from high resolution Digital Elevation Models (DEMs) based on Light Detection and Ranging (LiDAR) are investigated. A method for automatic extraction of valley and channel networks from high-resolution DEMs is presented. This method utilizes both positive (i.e., convergent topography) and negative (i.e., divergent topography) curvature to delineate the valley network. The valley and ridge skeletons are extracted using the pixels' curvature and the local terrain conditions. The valley network is generated by checking the terrain for the existence of at least one ridge between two intersecting valleys. The transition from unchannelized to channelized sections (i.e., channel head) in each 1st-order valley tributary is identified independently by categorizing the corresponding contours using an unsupervised approach based on K-means clustering. The method does not require a spatially constant channel initiation threshold (e.g., curvature or contributing area). Moreover, instead of a point attribute (e.g., curvature), the proposed clustering method utilizes the shape of contours, which reflects the entire cross-sectional profile including possible banks. The method was applied to three catchments: Indian Creek and Mid Bailey Run in Ohio, and Feather River in California. The accuracy of channel head extraction from the proposed method is comparable to state-of-the-art channel extraction methods. Valleys extracted from DEMs may be wet (flowing) or dry at any given time depending on the hydrologic conditions. The temporal dynamics of flowing streams are vitally important for understanding hydrologic processes including surface water and groundwater interaction and hydrograph recession. However, observations of wet channel networks are limited, especially in headwater catchments. Near infrared LiDAR data provide an opportunity to map wet channel networks owing to the fine spatial resolution and strong absorption of light energy by water surfaces. A systematic method is developed to map wet channel networks by integrating elevation and signal intensity of ground returns. The signal intensity thresholds for identifying wet pixels are extracted from frequency distributions of intensity return within the convergent topography extent using a Gaussian mixture model. Moreover, the concept of edge in digital image processing, defined based on the intensity gradient, is utilized to enhance detection of small wet channels. The developed method was applied to the Lake Tahoe area based on eight LiDAR acquisitions during recession periods in five watersheds. A power-law relationship between streamflow and wetted channel length during recession periods was derived, and the scaling exponent (L?Q^0.38) is within the range of reported values from fieldwork in other regions.Several studies in the past focused on the relationship between drainage density (i.e., drainage length divided by drainage area) and long-term climate and reported a U-shape pattern. In this dissertation, this relationship was re-visited and the effect of drainage area on drainage density was investigated. Long-term climate was quantified by climate aridity indices which is the ratio between long-term potential evaporation and precipitation. 120 study sites across the United States with minimal human disturbance and a wide range of climate aridity index were selected based on the availability of LiDAR data. The drainage networks were delineated from LiDAR-based 1 m DEMs using the proposed curvature-based method. Despite the U-shaped relationship in the literature, our result shows a significant decreasing trend in the drainage density versus climate aridity index in arid regions; whereas no trend is observed in humid watersheds. This observation and its discrepancy with the reported pattern in the literature are justified considering the dynamics of the runoff erosive force and the resistance of vegetation and the climate controls on them. Our findings suggest that natural drainage networks in arid regions are more sensitive to the change in long-term climate conditions compared with drainage networks in humid climate. It was also found that drainage density has a decreasing trend with drainage area in arid regions; however, no trend was observed in humid regions. In a broader sense, the findings influence our understanding of the formation of drainage networks and the response of hydrologic systems to climate change. The formation and growth of river channels and their network evolution are governed by the erosional and depositional processes operating on the landscape due to movement of water. The branching angles, i.e., the angle between two adjoining channels, in drainage networks are important features related to the network topology and contain valuable information about the forming mechanisms of the landscape. Based on channel networks extracted from 1 m Digital Elevation Models of 120 catchments with minimal human impacts across the United States, we showed that the junction angles have two distinct modes with ?1 ? 49.5(&)deg; and ?2 ? 75.0(&)deg;. The observed angles are physically explained as the optimal angles that result in minimum energy dissipation and are linked to the exponent characterizing slope-area curve. Our findings suggest that the flow regimes, debris-flow dominated or fluvial, have distinct characteristic angles which are functions of the scaling exponent of the slope-area curve. These findings enable us to understand the geomorphologic signature of hydrologic processes on drainage networks and develop more refined landscape evolution models.
Show less
Date Issued: 2017
Identifier: CFE0006604, ucf:51278
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006604

Title: Base Flow Recession Analysis for Streamflow and Spring Flow.
Creator: Ghosh, Debapi, Wang, Dingbao, Chopra, Manoj, Singh, Arvind, Medeiros, Stephen, Bohlen, Patrick, University of Central Florida
Abstract / Description: Base flow recession curve during a dry period is a distinct hydrologic signature of a watershed. The base flow recession analysis for both streamflow and spring flow has been extensively studied in the literature. Studies have shown that the recession behaviors during the early stage and the late stage are different in many watersheds. However, research on the transition from early stage to late stage is limited and the hydrologic control on the transition is not completely understood. In...
Show moreBase flow recession curve during a dry period is a distinct hydrologic signature of a watershed. The base flow recession analysis for both streamflow and spring flow has been extensively studied in the literature. Studies have shown that the recession behaviors during the early stage and the late stage are different in many watersheds. However, research on the transition from early stage to late stage is limited and the hydrologic control on the transition is not completely understood. In this dissertation, a novel cumulative regression analysis method is developed to identify the transition flow objectively for individual recession events in the well-studied Panola Mountain Research Watershed in Georgia, USA. The streamflow at the watershed outlet is identified when the streamflow at the perennial stream head approaches zero, i.e., flowing streams contract to perennial streams. The identified transition flows are then compared with observed flows when the flowing stream contracts to the perennial stream head. As evidenced by a correlation coefficient of 0.90, these two characteristics of streamflow are found to be highly correlated, suggesting a fundamental linkage between the transition of base flow recession from early to late stages and the drying up of ephemeral streams. At the early stage, the contraction of ephemeral streams mostly controls the recession behavior. At the late stage, perennial streams dominate the flowing streams and groundwater hydraulics governs the recession behavior. The ephemeral stream densities vary from arid regions to humid regions. Therefore, the characteristics of transition flow across the climate gradients are also tested in 40 watersheds. It is found that climate, which is represented by climate aridity index, is the dominant controlling factor on transition flows from early to late recession stages. Transition flows and long-term average base flows are highly correlated with a correlation coefficient of 0.82. Long-term average base flow and the transition flow of recession are base flow characteristics at two temporal scales, i.e., the long-term scale and the event scale during a recession period. This is a signature of the co-evolution of climate, vegetation, soil, and topography at the watershed scale. The characteristics of early and late recession are applied for quantifying human impacts on streamflow in agricultural watersheds with extensive groundwater pumping for irrigation. A recession model is developed to incorporate the impacts of human activities (such as groundwater pumping) and climate variability (such as evapotranspiration) on base flow recession. Groundwater pumping is estimated based on the change of observed base flow recession in watersheds in the High Plains Aquifer. The estimated groundwater pumping rate is found consistent compared with the observed data of groundwater uses for irrigation. Besides streamflow recession analysis, this dissertation also presents a novel spring recession model for Silver Springs in Florida by incorporating groundwater head, spring pool altitude, and net recharge into the existing Torricelli model. The results show that the effective springshed area has continuously declined since 1988. The net recharge has declined since the 1970s with a significant drop in 2002. Subsequent to 2002, the net recharge increased modestly but not to the levels prior to the 1990s. The decreases in effective springshed area and net recharge caused by changes in hydroclimatic conditions including rainfall and temperature, along with groundwater withdrawals, contribute to the declined spring flow.
Show less
Date Issued: 2015
Identifier: CFE0005951, ucf:50814
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005951

Title: Understanding Hydroclimatic Controls on Stream Network Dynamics using LiDAR Data.
Creator: Kim, Seoyoung, Wang, Dingbao, Medeiros, Stephen, Nam, Boo Hyun, Singh, Arvind, Sumner, David, University of Central Florida
Abstract / Description: This dissertation investigates the hydroclimatic controls on drainage network dynamics and characterizes the variation of drainage density in various climate regions. The methods were developed to extract the valley and wet channel networks based on Light Detection and Ranging (LiDAR) data including the elevation and intensity of laser returns. The study watersheds were selected based on the availability of streamflow observations and LiDAR data. Climate aridity index was used as a...
Show moreThis dissertation investigates the hydroclimatic controls on drainage network dynamics and characterizes the variation of drainage density in various climate regions. The methods were developed to extract the valley and wet channel networks based on Light Detection and Ranging (LiDAR) data including the elevation and intensity of laser returns. The study watersheds were selected based on the availability of streamflow observations and LiDAR data. Climate aridity index was used as a quantitative indicator for climate. The climate controls on drainage density were re-visited using watersheds with minimal anthropogenic interferences and compared with the U-shape relationship reported in the previous studies. A curvature-based method was developed to extract a valley network from 1-m LiDAR-based Digital Elevation Models. The relationship between drainage density and climate aridity index showed a monotonic increasing trend and the discrepancy was explained by human interventions and underestimated drainage density due to the coarse spatial resolution (30-meter) of the topographic maps used in previous research. Observations of wet channel networks are limited, especially in headwater catchments in comparison with the importance of stream network expansion and contraction. A systematic method was developed to extract wet channel networks based on the signal intensities of LiDAR ground returns, which are lower on water surfaces than on dry surfaces. The frequency distributions of intensities associated with wet surface and dry surface returns were constructed. With the aid of LiDAR-based ground elevations, signal intensity thresholds were identified for extracting wet channels. The developed method was applied to Lake Tahoe area during recession periods in five watersheds. A power-law relationship between streamflow and wet channel length was obtained and the scaling exponent was consistent with the reported findings from field work in other regions.Perennial streams flow for the most of the time during normal years and are usually defined based on a flow duration threshold. The streamflow characteristics of perennial streams in this research were assessed using the relationship between streamflow exceedance probability and wet channel ratio based on wet channel networks extracted from LiDAR data. Non-dimensional analysis based on the relationship between streamflow exceedance probability and wet channel ratio showed that results were consistent with previous research about perennial stream definition, and provided the possibility to use wet channel ratio to define perennial streams. Wetlands are important natural resources and need to be monitored regularly in order to understand their inundation dynamics, function and health. Wetland mapping is a key part of monitoring programs. A framework for detecting wetland was developed based on LiDAR elevation and intensity information. After masking out densely vegetated areas, wet areas were identified based on signal intensity of ground returns for barrier islands in East-Central Florida. The intensity threshold of wet surface was identified by decomposing composite probability distribution functions using a Gamma mixture model and the Expectation-Maximization algorithm. This method showed good potential for wetland mapping.The methodology developed in this dissertation demonstrated that incorporating LiDAR data into the drainage networks, stream network dynamics and wetlands results in enhanced understanding of hydroclimatic controls on stream network dynamics. LiDAR data provide a rich information source including elevation and intensity, and are of great benefit to hydrologic research community.
Show less
Date Issued: 2016
Identifier: CFE0006532, ucf:51372
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006532

Title: Annual water balance model based on generalized proportionality relationship and its applications.
Creator: Tang, Yin, Wang, Dingbao, Kibler, Kelly, Singh, Arvind, Sumner, David, Quintana-Ascencio, Pedro, University of Central Florida
Abstract / Description: The main goal of this dissertation research is to derive a type of conceptual models for annual water balance at the watershed scale. The proportionality relationship from the Soil Conservation Service Curve Number method was generalized to annual scale for deriving annual water balance model. As a result, a one-parameter Budyko equation was derived based on one-stage partitioning; and a four-parameter Budyko equation was derived based on two-stage partitioning. The derived equations balance...
Show moreThe main goal of this dissertation research is to derive a type of conceptual models for annual water balance at the watershed scale. The proportionality relationship from the Soil Conservation Service Curve Number method was generalized to annual scale for deriving annual water balance model. As a result, a one-parameter Budyko equation was derived based on one-stage partitioning; and a four-parameter Budyko equation was derived based on two-stage partitioning. The derived equations balance model parsimony and representation of dominant hydrologic processes, and provide a new framework to disentangle the roles of climate variability, vegetation, soil and topography on long-term water balance. Three applications of the derived equations were demonstrated. Firstly, the four-parameter Budyko equation was applied to 165 watersheds in the United States to disentangle the roles of climate variability, vegetation, soil and topography on long-term water balance. Secondly, the one-parameter Budyko equation was applied to a large-scale irrigation region. The historical annual total water storage change were reconstructed for assessing groundwater depletion due to irrigation pumping by integrating the derived equation and the satellite-based GRACE (Gravity Recovery and Climate Experiment) data. Thirdly, the one-parameter Budyko equation was used to model the impact of willow treatment on annual evapotranspiration through a two-year field experiment in the Upper St. Johns River marshes. An empirical relationship between the parameter and willow fractional coverage was developed, providing a useful tool for predicting long-term response of evapotranspiration to willow treatment. ?
Show less
Date Issued: 2017
Identifier: CFE0006958, ucf:51638
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006958

LiDAR (2)	+ -
Silver Springs (2)	+ -
groundwater depletion (2)	+ -
perennial stream (2)	+ -
sinkhole (2)	+ -

Asymmetry (1)	+ -
Base flow recession (1)	+ -
Budyko (1)	+ -
Carrying Capacity (1)	+ -
Channel network (1)	+ -
Climate (1)	+ -
Climatic and anthropogenic changes (1)	+ -
Curvature (1)	+ -
DEM (1)	+ -
Drainage density (1)	+ -
Evaporation (1)	+ -
Everglades (1)	+ -
GRACE (1)	+ -
High Plains Aquifer (1)	+ -
Hydrolog (1)	+ -
Hydrologic changes (1)	+ -
Ichetucknee (1)	+ -
Junction angle (1)	+ -
Living shorelines (1)	+ -
Panola Mountain Research Watershed (1)	+ -
Power spectral density (1)	+ -
Precipitation (1)	+ -
Quality (1)	+ -
Rainfall-Runoff (1)	+ -
Random Forest (1)	+ -

Singh, Arvind (13)	+ -
University of Central Florida (13)	+ -
Wang, Dingbao (10)	+ -
Medeiros, Stephen (6)	+ -
Nam, Boo Hyun (4)	+ -

Kibler, Kelly (3)	+ -
Chopra, Manoj (2)	+ -
Mayo, Talea (2)	+ -
Sandhu, Daljit (2)	+ -
Sumner, David (2)	+ -
Zheng, Qipeng (2)	+ -
Ahmed, Kareem (1)	+ -
An, Jin Woo (1)	+ -
Bhattacharya, Samik (1)	+ -
Bohlen, Patrick (1)	+ -
Faraji, Sarah (1)	+ -
Geikie, Marissa (1)	+ -
Ghosh, Debapi (1)	+ -
Hooshyar, Milad (1)	+ -
Kheimi, Marwan (1)	+ -
Kim, Seoyoung (1)	+ -
Perez, Adam (1)	+ -
Quintana-Ascencio, Pedro (1)	+ -
Rajabi, Amirarsalan (1)	+ -
Spiering, David (1)	+ -
Tahsin, Subrina (1)	+ -
Tang, Yin (1)	+ -
Vasu Sumathi, Subith (1)	+ -
Wahl, Thomas (1)	+ -
Weishampel, John (1)	+ -

Search In

Sort Results By:

Narrow results by:

Topical Subject

Collection

Type of Resource

Language

Creator

Format

Owner