Browsing by Subject "GIS"
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Item A GIS-based Bayesian approach for analyzing spatial-temporal patterns of traffic crashes(2009-06-02) Li, LinhuaThis thesis develops a GIS-based Bayesian approach for area-wide traffic crash analysis. Five years of crash data from Houston, Texas, are analyzed using a geographic information system (GIS), and spatial-temporal patterns of relative crash risk are identified based on a hierarchical Bayesian approach. This Bayesian approach is used to filter the uncertainty in the data and identify and rank roadway segments with potentially high relative risks for crashes. The results provide a sound basis to take preventive actions to reduce the risks in these segments. To capture the real safety indications better, this thesis differentiates the risks in different directions of the roadways, disaggregates different road types, and utilizes GIS to analyze and visualize the spatial relative crash risks in 3-D views according to different temporal scales. Results demonstrate that the approach is effective in spatially smoothing the relative crash risks, eliminating the instability of estimates while maintaining real safety trends. The posterior risk maps show high-risk roadway segments in 3-D views, which is more reader friendly than the conventional 2-D views. The results are also useful for travelers to choose relatively safer routes.Item Abundance and distribution trends of the West Indian manatee in the coastal zone of Belize: implications for conservation.(Texas A&M University, 2004-09-30) Auil, Nicole EricaThe coastal zone of Belize is home to the largest recorded number of the threatened Antillean manatee (Trichechus manatus manatus) within the species' Caribbean range. The objectives of my study were: (1) to determine long-term trends in aerial survey counts and indices of the manatee population in the coastal zone of Belize; and (2) to examine the seasonal change in manatee distribution among habitats in the coastal zone. Standardized extended-area aerial surveys were conducted along the entire coastline of Belize in the dry and wet seasons of 1997, and 1999 - 2002. Manatees were counted in five habitat categories: cay, coast, estuary, lagoon, and river. Total sightings per survey ranged from 90 to 338; the greatest number was counted in the 2002 wet season. Calf percentage ranged from 5 to 13. A slight negative trend in total counts was significant for dry-season, not wet-season surveys, indicating an interactive effect of season and year. Based on analysis of variance, the Abundance Index (transformed manatee sightings per hour) did not differ significantly among years, although it varied significantly within year by season and habitat by season. In applying a spatial approach, the general survey route was buffered 1 km on both sides, and 1 km grids were overlaid and classified by habitat type. The presence or absence of each cell for each survey was used in likelihood ratio tests of the single and interactive effect of season and habitat. The Index for river habitat was higher in the dry season, while cay habitat was higher in the wet season. Overall, near-shore habitat (estuary, lagoon, and river) showed a higher Index than did the offshore habitat (cay and coast) although the total number of sightings was higher offshore. Considering the interactive effect of year, season, and habitat, long-term studies are needed, in both seasons, and among all habitats to account for variation. Continued broad-scale surveys, along with metapopulation analysis would fine-tune the understanding of specific sites, enhancing integrated coastal zone management for protected species and their habitat systems.Item An exploration of the relationship between use of parks and access, park appeal, and communication effectiveness(2009-05-15) Walker, Jamie RaeUnderstanding what variables influence park use would assist park providers and policy makers in acquiring, designing, managing, and funding initiatives which encourage or support park use. Previous studies indicate that access to parks (measured by both objective and perceived distances), park appeal in terms of being well-maintained, and effective communication between constituents and park suppliers, relate positively to park use. This study explores the relationships between access, appeal, and communication and park use. Access is operationalized as four objective distances from household to nearest park using both Euclidian and Network measures, and by subjective self-reported measures of ability to access parks on foot or by bicycle. Appeal is concerned with the influence of parks? perceived level of maintenance and availability of amenities on the probability of park use. Effective communication is operationalized by three variables: perceptions of being well-informed, being included in the planning process, and being able to give feedback to park leaders. These variables and selected demographic data were extracted from an existing data set: the City of College Station Needs Assessment. Findings indicated that a) respondents with access to parks are more likely to use parks, b) level of maintenance and available amenities influenced use, and c) respondents who are well-informed are more likely to use parks.Item Analyzing the connectivity potential of landscape geomorphic systems: a radar remote sensing and GIS approach, Estufa Canyon, Texas, USA(Texas A&M University, 2005-11-01) Ibrahim, ElSayed Ali HermasConnectivity is considered one of the fundamental aspects that influences the rate of mass movement in the landscape. The connectivity aspect has been acknowledged from various conceptual geomorphic frameworks. None of these provided a developmental methodology for studying the connectivity of geomorphic systems, especially at the scale of the fluvial system. The emphasis in this research is placed on defining variables of the geomorphic systems that influence the connectivity potential of these systems. The landscape gradient, which is extracted from the Digital Elevation Model (DEM), and the surface roughness, which is extracted from radar images, are used to analyze the connectivity potential of geomorphic systems in the landscape. Integration of these variables produces a connectivity potential index of the various geomorphic systems that compose the fluvial system. High values of the connectivity potential index indicate high potential of the geomorphic system to transport mass whereas the low values indicate low potential of the geomorphic system to transport mass in the landscape. Using the mean values of the connectivity potential index, the geomorphic systems in the landscape can be classified into geomorphic systems of low connectivity potential, geomorphic systems of intermediate connectivity potential and geomorphic systems of high connectivity potential. In addition to the determination of the relative connectivity potential of various geomorphic systems, the connectivity potential index is used to analyze the system-wide connectivity. The ratios between the connectivity potential index of the upstream geomorphic systems and the connectivity potential index of the downstream geomorphic systems define system-wide connectivity in the landscape. High ratios reflect the high potential of the upstream geomorphic systems to transport mass in the downstream direction. Low ratios indicate the influence of the downstream geomorphic systems in maximizing mass movement in the upstream geomorphic systems. The presence of high and low ratios suggests the presence of a high system-wide connectivity. As the ratio approaches unity, mass movement is minimized in the landscape indicating low system-wide connectivity. Applying the above approach to Estufa Canyon, Texas, illustrated that Estufa Canyon is a dynamic fluvial system with high system-wide connectivity.Item Austin's route forward : an exploration of alternative demand estimation and the transit planning process(2015-05) Mosteiro, Jonathan David; Jiao, Junfeng; Machemehl, RandyAlternative demand estimation techniques for transit planning have gained increased attention in recent years. These "sketch planning" models are often faster and easier to use than traditional four-step travel demand models, and can therefore play a significant role in preliminary feasibility analyses for major fixed-guideway transit planning initiatives. This paper uses one such sketch planning tool produced by Transit Cooperative Research Program (TCRP) Report 167 to explore ridership potential along two light rail corridors in the City of Austin. Planners recently completed a planning process for an initial segment of urban rai in central Austin that was ultimately defeated by voters in a 2014 bond election called to fund the project. The ridership results produced by the Report 167 model corroborate some claims made by transit advocates who opposed Proposition 1 that the highest ridership route was not advanced to voters in the election. By using a sketch planning tool to compare ridership along the ill-fated Project Connect route to a route advocated by critics of the process, this paper also provides insight into the role that sketch planning can play in the transit planning process, both generally and in the context of rail planning efforts in Austin.Item Bacterial total maximum daily load (TMDL): development and evaluation of a new classification scheme for impaired waterbodies of Texas(Texas A&M University, 2005-02-17) Paul, SabuUnder the Clean Water Act (CWA) program the Texas Commission on Environmental Quality (TCEQ) listed 110 stream segments with pathogenic bacteria impairment in 2000. The current study was conducted to characterize the watersheds associated with the impaired waterbodies. The main characteristics considered for the classification of waterbodies were designated use of the waterbody, land use distribution, density of stream network, average distance of a land of a particular use to the closest stream, household population, density of on-site sewage facilities (OSSF), bacterial loading due to the presence of different types of farm animals and wildlife, and average climatic conditions. The availability of observed in-stream fecal coliform bacteria concentration data was evaluated to obtain subgroups of data-rich and data-poor watersheds within a group. The climatic data and observed in-stream fecal coliform bacteria concentrations were analyzed to find out seasonal variability of the water quality. The watershed characteristics were analyzed using the multivariate statistical analysis techniques such as factor analysis/principal component analysis, cluster analysis, and discriminant analysis. Six groups of watersheds were formed as result of the statistical analysis. The main factors that differentiate the clusters were found to be bacterial contribution from farm animals and wildlife, density of OSSF, density of households connected to public sewers, and the land use distribution. Two watersheds were selected each from two groups of watersheds. Hydrological Simulation Program-FORTRAN (HSPF) model was calibrated for one watershed within each group and tested for the other watershed in the same group to study the similarity in the parameter sets due to the similarity in watershed characteristics. The study showed that the watersheds within a given cluster formed during the multivariate statistical analysis showed similar watershed characteristics and yielded similar model results for similar model input parameters. The effect of parameter uncertainty on the in-stream bacterial concentration predictions by HSPF was evaluated for the watershed of Salado Creek, in Bexar County. The parameters that control the HSPF model hydrology contributed the most variance in the in-stream fecal coliform bacterial concentrations corresponding to a simulation period between 1 January 1995 and 31 December 2000.Item Behavioral ecology and conservation of large mammals: historical distribution, reintroduction and the effects of fragmented habitat(2009-05-15) Gilad, OranitConservation biologists have used reintroduction as a method to reestablish extirpated species in their native habitat. Three important aspects of a successful reintroduction effort include: (1) a habitat suitability study of the reintroduction area, including effects of migration corridors; (2) identification of possible predators of the reintroduced species; and (3) a post-reintroduction assessment including an evaluation of the species' population dynamics. In this study I examine the suitability of Guadalupe Mountains National Park (GUMO) as a reintroduction area for desert bighorn sheep. The study used landscape metrics to compare GUMO to a nearby mountain range that is currently supporting an estimated population of 400 bighorn sheep. This study identified migration corridors for bighorns throughout the region and evaluated mountain lion (a potential predator of bighorn sheep) numbers either residing in or passing through the park between the years 1997 to 2004. Results on the studies in GUMO revealed 15,884 ha of suitable habitat for bighorn sheep and provided evidence of migration routes between GUMO and neighboring mountain ranges. In terms of potential predators, a minimum of 32 resident and/or transient mountain lions occurred in GUMO over a seven year period, and a minimum of 15 cats used the park in 2002. Based on estimates of individual home range of males and females, GUMO should be able to support four to five individuals. The genetic data indicates a high number of transients or perhaps an unstable population of mountain lions that may be the result of intense hunting pressure of cats in Texas. Finally, my study simulates parameters of the population dynamics of a different species, the Arabian oryx that was reintroduced as three separate populations to the Israeli Negev between 1998 and 2005. I simulated population growth and the effect of migration corridors on species persistence. Results suggest that migration corridors are essential for a self-sustaining viable metapopulation under current natality rates. In the event that natality rates increase (as was evident in a reintroduced population of Arabian oryx in Oman), metapopulation can reach viable size with only two of the release sites (open, flat terrain) connected by migration corridors.Item The choice to walk, a parcel & network based analysis of pedestrian access and income in Austin, TX(2012-08) Glass, Laura Kristen; McCray, Talia; Zhang, MingWalkability is desirable for a variety of reasons. Sometimes, walkability is desirable because it is the only available or affordable transportation modal choice. Urban form and transportation infrastructure can be hostile to pedestrians because cars are prioritized first, and pedestrians often face unsafe situations and a lack of pedestrian facilities. This analysis explores a spatial distribution of pedestrian access to opportunities in Austin, TX, and examines the locations of households of different income levels relative to areas of high pedestrian access to opportunities. To achieve results that are equally precise across the study area, this analysis employs GIS analysis and U.S. Census 2000 data, and analyzes the study area using a ½ square-mile grid system. High pedestrian access areas are defined as locations where residential parcels have pedestrian network access to multiple types of opportunities and above average number of opportunities. This analysis finds that low income households are more associated with high pedestrian access areas in Austin, TX, than moderate and high income households. If lower income households are consistently shown to rely more on pedestrian infrastructure than moderate or high income households, it may be important to allocate funding to high pedestrian access areas with low income populations in such a way that is socially equitable, and that will result in more use of the pedestrian facilities.Item City and regional planning software in context : a rating framework for Planning Support Systems(2009-12) Phelan, Chad Maclay; Moore, Steven A., 1945-; Paterson, RobertThe difficulty of projecting ecological impacts, as well as the increasing familiarity of planners with Geographical Information Systems and other software technology has led to an increase in the use of Planning Support Systems (PSS) by city and regional planners. Due to their newness and rapid development, there is, of yet, a lack of a comprehensive peer-reviewed literature on the design and implementation of these systems. This thesis proposes and applies a rating framework for PSS in order to facilitate accessibility to and critical investigation of PSS. The rating framework’s criteria are based on the “seven sins” of comprehensive land use models identified by Douglass Lee’s 1973 article “Requiem for Large-Scale Models."Item Constructing a GIS-based 3D urban model using LiDAR and aerial photographs(Texas A&M University, 2005-02-17) Lin, Wei-MingDue to the increasing availability of high-resolution remotely sensed imagery and detailed terrain surface elevation models, urban planners and municipal managers can now model and visualize the urban space in three dimensions. The traditional approach to the representation of urban space is 2D planimetric maps with building footprints, facilities and road networks. Recently, a number of methods have been developed to represent true 3D urban models. Those include panoramic imaging, Virtual Reality Modeling Language (VRML), and Computer-aided Design (CAD). These methods focus on aesthetic representation, but they do not have sufficient spatial query and analytical capabilities. This research evaluates the conventional approaches to 3D urban models, and identifies their advantages and limitations; GIS functionalities have been combined with 3D urban visualization techniques to develop a GIS-based urban modeling method; The algorithms and techniques have been explored to derive urban objects and their attributes from airborne LiDAR and high-resolution imagery for constructing and visualizing 3D urban models; and 3D urban models for the Texas A&M University (TAMU) campus and downtown Houston have been implemented using the algorithms and techniques developed in this research. By adding close-range camera images and highresolution aerial photographs as the texture of urban objects, effect of photorealism visualization has been achieved for walk-through and fly-through animations. The Texas A&M University campus model and the downtown Houston model have been implemented to offer proof-of-concept, namely, to demonstrate the advantages of the GIS-based approach. These two prototype applications show that the GIS-based 3D urban modeling method, by coupling ArcGIS and MultiGen-Paradigm Site Builder 3D software, can realize the desired functionalities in georeferencing, geographical measurements, spatial query, spatial analysis, and numerical modeling in 3D visual environment.Item Coupling of Backbarrier Shorelines to Geomorphological Processes(2013-08-14) Trimble, Sarah MargaretRecent evidence suggests that backbarrier structure may act as an historical record of island development, and that backbarrier shorelines can be used as a proxy of an island?s past and future transgressive response to sea-level rise. The structure and stability of back-barrier shorelines are dependent on the geologic framework, defined here as the combination of nearshore topography, underlying geology, and modern geomorphologic forces. This antecedent framework controls and influences the present morphology, nearshore dynamics, and rates of transgression in response to sea-level rise while also acting as a feedback to the estuary ecology on the bayside. It is therefore surprising that our understanding of backbarrier geomorphology is limited. There is a need for an established link between process regimes and an island?s geomorphological history. This thesis bridges the current intellectual gap. The primary hypothesis of this project is that shorelines and bathymetric isolines share quantitative shape signatures indicative of their shared morphological past. To establish this link, the backbarrier shorelines of four United States National Seashores (Fire Island, NY; Assateague Island, MD; Santa Rosa Island, FL; and North Padre Island, TX) are digitized from aerial imagery using the marshline as the shoreline indicator to ensure the inclusion of (vital, sometimes inundated) ecosystems and sediment storage. The alongshore variation of this backbarrier shoreline, the mainland shoreline, lagoon bathymetry, and nearshore bathymetry are each quantified through wavelet analysis and their shape signatures are examined for spatial correspondence. Large and small scale variations are identified and attributed to the geomorphologic controls operating on the same scale and alongshore variation. The result is an improved understanding of how the geologic framework controls backbarrier shoreline shape, which is essentially an expression of the underlying geology.Item Creation and customization of a GIS-based traffic control planning tool(2011-12) Goldberg, Brian Scott; Machemehl, Randy B.; Zhang, ZhanminThe purpose of this study is to develop a tool that will assist in the development of traffic control plans. Using information from TxDOT Dallas District and several other sources, a GIS-based map has been assembled that combines data from many different formats into one user-friendly environment. The capability provided in the tool includes geometric properties of all TxDOT-controlled freeway segments, as well as daily and hourly demand data and capacity information specific to both general and HOV lanes. By selecting a segment on the map and opening the tool, the user can easily navigate through the collection of data in just seconds, which will significantly reduce the amount of time required by the traffic engineer to gather site-specific information when analyzing temporary traffic control.Item Defining GeoDesign and the emergent role of the sustainable sites initiative (SITES) for integrative project management(2012-08) Risinger, Emily Diane; Lee, Ming-ChunThis report is a discussion of the multifarious applications of the modern day geographic information system and how the universal merit of the technology across disciplines has led to the emergence of GeoDesign. The purpose of this Master’s Professional Report was to retrace the core conceptual framework and landmark events occurring in the evolution GIS technology, and how these factors have led to recent creation of new performance based rating systems and evidence-based design techniques. The Sustainable Sites Initiative (SITES), a new performance based rating system that has emerged in response to the call for increased knowledge and best practices lacking in LEED, is discussed; along with integrated project management. This professional report was intended to be an exploratory discussion of the larger theoretical implications fueling the shift towards mandating greater standards for sustainable design. It offers some ideas for how we should continue evolving GeoDesign moving into the next century; and outlines the importance of all new rating systems needing to acknowledge the growing importance of GeoDesign and ever advancing imagery technologies in understanding complex system processes in the future.Item Delineating wetlands using geographic information system and remote sensing technologies(Texas A&M University, 2006-04-12) Villeneuve, JulieDuring the last century wetlands have considerably decreased. The principal cause is urbanization, especially in large urban regions such as the Houston area. In order to protect the remaining wetlands, they have to be monitored carefully. However monitoring wetland is a difficult and time-demanding task because it has to be done repetitively on large areas to be effective. This study was conducted to determine if Geographical Information System (GIS) and remote sensing technologies would allow accurate monitoring of wetland as a less time-consuming method. With this idea, a suitability model was developed to delineate wetlands in the Houston area. This model combined GIS and remote sensing technologies. The data used for this study were as high spatial resolution as possible and were generally easy to obtain. This suitability model consisted of four submodels: hydrology, soil, vegetation and multi- attribute. Each submodel generated a Wetland Suitability Index (WSI). Those WSI were summed to obtain a general WSI. The suitability model was calibrated using half of the study area. During calibration, the general model was evaluated as well as each individual index. Generally, the model showed a lack of sensitivity to changes. However, the model was slightly modified to improve the delineation of upland wet- lands by increasing the weight of the soil submodel. This model was validated using the second half of the study area. The validation results improved a bit compared to the calibration results; however they remained weak. It was demonstrated that the model does not favor riverine wetlands over upland wetlands, nor large size wetlands. The model ground truth data were evaluated and were suffciently proven to be up to date. Those results indicated that the weakness of the model must come from inac- curacy in the input data. Therefore, the study showed that while existing computing capacity supports remote delineation, spatial accuracy is still insuffcient to perform correct wetland delineation using remote sensing and GIS technologies.Item Demonstration and analysis of tangible heritage management strategy using geographical information systems for the city of Al-Ain, United Arab Emirates(Texas A&M University, 2006-10-30) Al Zaabi, Azza HasanThe United Arab Emirates (UAE) is focusing on towards two paradoxical directions especially after the oil-boom. The first is the contemporary architectural development, while the second is the conservation of traditional dwellings and historical sites in the country. It is obvious that the management and planning towards the first direction are fully integrated and highly pr????cised to be implemented efficiently, thus, unveiling a new fa????ade of contemporary lifestyle to the world. But the second direction is lacking good strategic efforts for conservation, preservation methods and tourism promotion, especially among different authorities that are in charge of either management or implementation of conservation techniques. Therefore, the country started looking for solutions that initiate the right management strategy to be followed and improve the use and promotion of tangible heritage. In this research, I am taking the case of the city of Al-Ain since it has started taking the path and has established an agreement with UNESCO. Geographical Information Systems is used in this research as a tool to implement the major objectives and solutions for issues discussed in the agreement. In this research, the main issues that were discussed in the agreement were segregated and studied separately in terms of geographic extent, then, spatially represented on the map. Furthermore, they were analyzed using the different techniques in the Geographical Information Systems software ArcGIS to demonstrate each issue and problem and study its expected results. It was clear from this research that these issues were clearly presented using the software and will aid in the decision making process, especially for stakeholders and different entities in the city of Al Ain.Item Determining existing, possible, and preferable urban tree canopy for Austin, Texas(2013-05) Halter, Alan Dale; Lee, Ming-ChunThis report analyzes urban tree canopy cover (UTC) in Austin, Texas in 2006 using a Geographic Information System (GIS) geoprocessing method developed by the U.S. Forest Service. Findings reveal where UTC exists, could exist, and where it could be prioritized (physically speaking) throughout the Austin region. Results are explained through the context of natural regions and land use to further characterize the urban forest distribution with the purpose of gaining valuable big-picture insights as to where environmental benefits have resulted from local land use planning decisions, development tendencies, and forestry management practices in Austin.Item Developing a GIS-based intersection traffic control planning tool(2012-12) Bringardner, Jack William; Machemehl, Randy B.; Boyles, StephenThe purpose of this study was to include consideration for intersections into the previously created GIS traffic control planning tool. Available data for making intersection control calculations were collected and integrated into the design of the tool. The limitations created by required assumptions were addressed, as well as more advanced techniques for overcoming these problems. The tool can be use to estimate capacity calculations at any signalized intersection within the NCTCOG modeling region. These calculations can be used to inform users about the effects of a construction plan. Inputs for using dynamic traffic assignment to further understand these effects is then addressed, focusing on the development of a subnetwork to reduce computation time for multiple temporary traffic control plans.Item The development of a geotechnical GIS-based database in Austin, TX(2011-05) Lawrence, Robert Hoff; Gilbert, Robert B. (Robert Bruce), 1965-; Maidment, David R.Geographic Information Systems (GIS) are useful in analyzing and visualizing database information. Specifically, the field of geotechnical engineering stands to benefit from a database encompassing GIS; as, geotechnical data varies spatially. The City of Austin Water Utility realized the advantages of a geotechnical database utilizing GIS which led to the motivation of designing a database for Austin, Texas. The main objective is to provide a detailed explanation of the design of a GIS-relational geotechnical database for Austin, Texas. In addition, several examples of useful methods of analyzing geotechnical data spatially are included. The examples show the identification of faults, the uses of structural contour maps, summarization of data through plots and tables, and analyzing temporal piezometric conditions. The idea of a database is to organize and store data in a basic efficient format so that information is not duplicated. Database queries are then used to combine and rearrange the data within the database through relationships. The queries are then connected to GIS for intelligent visualization. This process is designed specifically for the geologic conditions that exist in Austin, Texas. Understanding the geotechnical engineering state of practice is important when designing a database that will encompass geotechnical data for a given region. The City of Austin relies on experience and the geotechnical report filing systems to initially plan future projects around geologic conditions. With the help of a geotechnical database, the information from geotechnical reports is a “computer click” away. Also, the geotechnical data from multiple reports is viewable at one time in both a 2 and 3 dimensional environments through GIS. Database features coupled with GIS tools proves to be an effective way for engineers and geologists to use geotechnical data.Item Development of an ArcGIS interface and design of a geodatabase for the soil and water assessment tool(Texas A&M University, 2004-09-30) Valenzuela Zapata, Milver AlfredoThis project presents the development and design of a comprehensive interface coupled with a geodatabase (ArcGISwat 2003), for the Soil and Water Assessment Tool (SWAT). SWAT is a hydrologically distributed, lumped parameter model that runs on a continuous time step. The quantity and extensive detail of the spatial and hydrologic data, involved in the input and output, both make SWAT highly complex. A new interface, that will manage the input/output (I/O) process, is being developed using the Geodatabase object model and concepts from hydrological data models such as ArcHydro. It also incorporates uncertainty analysis on the process of modeling. This interface aims to further direct communication and integration with other hydrologic models, consequently increasing efficiency and diminishing modeling time. A case study is presented in order to demonstrate a common watershed-modeling task, which utilizes SWAT and ArcGIS-SWAT2003.Item Development of indices for agricultural drought monitoring using a spatially distributed hydrologic model(Texas A&M University, 2005-11-01) Narasimhan, BalajiFarming communities in the United States and around the world lose billions of dollars every year due to drought. Drought Indices such as the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI) are widely used by the government agencies to assess and respond to drought. These drought indices are currently monitored at a large spatial resolution (several thousand km2). Further, these drought indices are primarily based on precipitation deficits and are thus good indicators for monitoring large scale meteorological drought. However, agricultural drought depends on soil moisture and evapotranspiration deficits. Hence, two drought indices, the Evapotranspiration Deficit Index (ETDI) and Soil Moisture Deficit Index (SMDI), were developed in this study based on evapotranspiration and soil moisture deficits, respectively. A Geographical Information System (GIS) based approach was used to simulate the hydrology using soil and land use properties at a much finer spatial resolution (16km2) than the existing drought indices. The Soil and Water Assessment Tool (SWAT) was used to simulate the long-term hydrology of six watersheds located in various climatic zones of Texas. The simulated soil water was well-correlated with the Normalized Difference Vegetation Index NDVI (r ~ 0.6) for agriculture and pasture land use types, indicating that the model performed well in simulating the soil water. Using historical weather data from 1901-2002, long-term weekly normal soil moisture and evapotranspiration were estimated. This long-term weekly normal soil moisture and evapotranspiration data was used to calculate ETDI and SMDI at a spatial resolution of 4km ?? 4km. Analysis of the data showed that ETDI and SMDI compared well with wheat and sorghum yields (r > 0.75) suggesting that they are good indicators of agricultural drought. Rainfall is a highly variable input both spatially and temporally. Hence, the use of NEXRAD rainfall data was studied for simulating soil moisture and drought. Analysis of the data showed that raingages often miss small rainfall events that introduce considerable spatial variability among soil moisture simulated using raingage and NEXRAD rainfall data, especially during drought conditions. The study showed that the use of NEXRAD data could improve drought monitoring at a much better spatial resolution.