Yaw A. Twumasi

The applications of GIS in the analysis of the impacts of human activities on south Texas watersheds.

With water resource planning assuming greater importance in environmental protection efforts, analyzing the health of agricultural watersheds using Geographic Information Systems (GIS) becomes essential for decision-makers in Southern Texas. Within the area, there exist numerous threats from conflicting land uses. These include the conversion of land formerly designated for agricultural purposes to other uses. Despite current efforts, anthropogenic factors are greatly contributing to the degradation of watersheds. Additionally, the activities of waste water facilities located in some of the counties, rising populations, and other socioeconomic variables are negatively impacting the quality of water in the agricultural watersheds. To map the location of these stressors spatially and the extent of their impacts across time, the paper adopts a mix scale method of temporal spatial analysis consisting of simple descriptive statistics. In terms of objectives, this research provides geo-spatial analysis of the effects of human activities on agricultural watersheds in Southern Texas and the factors fuelling the concerns under the purview of watershed management. The results point to growing ecosystem decline across time and a geographic cluster of counties experiencing environmental stress. Accordingly, the emergence of stressors such as rising population, increased use of fertilizer treatments on farm land, discharges of atmospheric pollutants and the large presence of municipal and industrial waste treatment facilities emitting pathogens and pesticides directly into the agricultural watersheds pose a growing threat to the quality of the watershed ecosystem.

Application of remote sensing and GIS technologies to assess the impact of surface mining at Tarkwa, Ghana

The industrial and small-scale mining industries have provoke serious environmental degradation in the form of deforestation, soil erosion and soil and water contamination by Hg and other heavy metals. Remote sensing and GIS technologies were used to investigate the temporal and spatial extent of environmental degradation from 1986 to 2000 in the Tarkwa mining area. While most of the study area was a healthy ecosystem in 1986, by 2001, over 60% of the land was degraded to the point where it could not be used for any commercial activity. An additional 35,000 ha of land has been polluted and remediation would be very expensive. This state of environmental degradation through mining activities was further aggravated by extreme human population encroachment of the region. This study puts into perspective the need for the government to institute strict environmental regulations to protect mining areas.

Mapping seasonal hazards for flood management in Accra, Ghana using GIS

The Greater Accra Metropolitan area experiences seasonal floods almost every year. Widespread rains characteristic of the May-July wet season, Accras low elevation, the clayish nature of its soil, inadequate and undersized drains, the dumping of refuse into drains and water bodies, and the development of environmentally sensitive areas are the major causes of flooding in the city. This paper reports an investigation into the application of the geographic information systems (GIS) and other technologies for mapping urban flood zones in Accra for managing urban flood hazards. GIS-based software was used to process and analyse the slope. The results revealed notable flood risk zones and watercourses in the study area. The identification of flood-prone zones will assist city planners and managers in locating where to establish measures to deal with: the problem. It will also help emergency response teams identify areas in which to focus their operations during times of flooding.

Using GIS in Ecological Management: Green Assessment of the Impacts of Petroleum Activities in the State of Texas

Geo-information technologies are valuable tools for ecological assessment in stressed environments. Visualizing natural features prone to disasters from the oil sector spatially not only helps in focusing the scope of environmental management with records of changes in affected areas, but it also furnishes information on the pace at which resource extraction affects nature. Notwithstanding the recourse to ecosystem protection, geo-spatial analysis of the impacts remains sketchy. This paper uses GIS and descriptive statistics to assess the ecological impacts of petroleum extraction activities in Texas. While the focus ranges from issues to mitigation strategies, the results point to growth in indicators of ecosystem decline.

The use of GIS and remote sensing techniques as tools for managing nature reserves: the case of Kakum National Park in Ghana

Failing prices in export commodities especially in sub-Saharan Africa has compelled countries like Ghana to explore its forests and wildlife reserves for foreign exchange. The forests are now under constant threat from fire, drought and the activities of local community groups. The management of these forest reserves thus faces severe problems. Current techniques for monitoring the forests in Ghana are ineffective, inconsistent, ad hoc and unreliable. The data collection is slow and often does not lend itself to a comprehensive analysis. Using satellite remote sensing (RS) coupled with geographic information system (GIS) technologies have provided the capabilities to develop a database of information that permits systematic monitoring and an effective means of protecting the Kakum National Park in Ghana from the encroachment of local communities. Classifying the digital elevation model (DEM) for Kakum, shows the ro/spl circ/les the model plays in estimating park accessibility. The information conveyed in the DEM is of immediate assistance to park planners. A low accessibility will be associated with high elevation. The map information also shows where the park is most likely to experience damage from tourist and other activities. The use of slope and aspect maps provided an additional tool for management of the park. The depiction of slope, for instance indicated whether certain elevations faced enhanced fire risk or other hazards. The integration of SPOT satellite data with information from topographical data permitted the immediate display of terrain gradients, showing where most damage may occur due to height. This paper highlights the reports of benefits that accrued from employing RS and GIS as management tools for forest and wildlife preservation in Ghana.

Investigation of the impact of urban sprawl in three Sahelian cities using remotely-sensed information

Rapid urban growth and the environmental, social and political consequences are major issues in Africa, especially in the major Sahelian cities. Using remote sensing technologies, it has been established that between 1980-2000, the rate of urbanization more than doubled in the capital city of Burkina Faso (118% increase) and nearly doubled in capitals of Mali (62%) and Niger (63% increase). There has been a drastic conversion of vegetated and open lands to urban and residential use. Population in these cities also grew significantly, clearly outpacing the overall population growth of the countries. Data obtained is useful in policy issues related to sustainable urban planning and also serves as input into urban growth to predict patterns of future urban expansion.

Spatial epidemiology risk assessment for rehabilitated former asbestos mining areas in Limpopo Province, South Africa, using remote sensing and conventional analytical methods

The aim of this study was to conduct a comparative analysis using remote sensing and conventional sample analysis to assess asbestos pollution in rehabilitated former asbestos mining areas. The study focused on the Mafefe and Mathabatha areas of Limpopo Province, South Africa. Field-based remote sensing techniques were used to spectrally differentiate various types of asbestos minerals in order to determine their efficacy in assessing asbestos pollution. X-ray diffraction and scanning electron microscopy were employed for the identification and characterisation of traces of asbestos minerals in soil and water samples collected from the rehabilitated areas. The samples were also examined using in situ remote sensing. An Analytical Spectral Devices field spectrometer was used for spectral analysis of asbestos minerals and that of soil and water samples to compare and validate reflectance spectroscopy findings with laboratory results. Results show that in situ remote sensing techniques are able to reveal traces of asbestos minerals on rehabilitated dry surface areas, suggesting that they can play a significant role in monitoring the distribution of the asbestos minerals for epidemiological risk assessment. However, the spectral characteristics of asbestos minerals in the water medium were not as distinct as compared to laboratory methods. Overall, the results show potential for using remote sensing techniques in spatial epidemiology studies.

The use of Remote Sensing to Detect Asbestos Mining Degradation in Mafefe and Mathabatha, South Africa

This study employs remote sensing to investigate the extent of degradation caused by asbestos mining, and to monitor the progress of mine rehabilitation in the Mafefe and Mathabatha areas in South Africa. Image differencing method (NDVI) was used to assess the condition of vegetation in the study area. Results show both positive and negative increase in vegetation at Mafefe and Mathabatha. The study helps in identifying areas that needs further rehabilitation.

The use of satellite imagery in rangeland management: a comparative analysis of three Sahelian zones

Among the most vulnerable environments in Africa are the rangelands of the Sahel. This study compiles a sequential database designed to clarify how Sahelian rangelands are changing and in response to what factors. Also reviewed are common theories about how rangelands are affected by drought, for example by use of misguided methods of farming. The most important policy recommendation on rangelands is that governments advocate and plan for public participation in solving the problem. In addition, governments should foster monitoring and analysis procedures which are national in scope compatible with global approaches.

Comparative analysis of reflectance spectroscopy and laboratory based assessment of asbestos pollution in the rehabilitated mining environment, South Africa

Asbestos minerals (Amosite, Crocidolite, Chrysotile, Tremolite, Anthophylite) were mined extensively in South Africa for more than ninety years. The mines were later closed because of the negative health and environmental impacts, thereafter commissioning the mine rehabilitation process in 1986. Since then, there has not been an effectively coordinated monitoring procedure to assess the progress of mine rehabilitation in mitigating asbestos pollution. Field evidence shows that traces of different asbestos minerals appear scattered even after the rehabilitation process has been conducted. This study uses remote sensing techniques to spectrally distinguish different types of asbestos minerals in the post-mining environment for use in pollution monitoring. Laboratory based techniques (X-Ray diffraction and scanning electron microscopy) were performed to detect the presence of asbestos minerals in soil and water of the rehabilitated environments. Analytical spectral devices (ASD) field spectrometer was used to collect spectra of asbestos minerals and that of soil and water samples analyzed in the laboratory in order to detect the presence of these minerals using spectral characteristics, and to compare the output with laboratory results. Results show that very low quantities of asbestos in water (<1 ppm) cannot be clearly detected using spectral data. The results were correlated to examine the potential use of remote sensing techniques in monitoring the asbestos polluted environment.