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(7a) Environmental hazard can be defined as the disasters which affect lives and properties within environment as a result of the action of man and other natural phenomenon.
(i) It exposes the land to soil erosion
(ii) It leads to reduction of soil nutrients
(iii) It brings about deterioration of environment
(iv) It discourages the act of keeping wildlife
(i) It affects the growth of plants
(ii) It leads to high loss of crops and livestock
(iii) It brings about up and down movement of animals and man or migration
(iv) It brings about surface dry up of rivers and streams
-Unloading; This is the release of stress in a rock that produces expansion joints can cause exfoliation. In other words reduction in stress occurs when rocks previously buried deeply are exposed due to erosion of overlying rocks, or when ice sheets that bury rocks melt.
-Exfoliation; is the term used to describe the peeling away of sheets of rock millimeters to m eters in thickness from a rock’s surface due a range of physical and chemical processes during exhumation and weathering.
Action of Plants and animals; can be agents of mechanical weathering. In other words the seed of a tree may sprout in soil that has collected in a cracked rock. As the roots grow, they widen the cracks, eventually breaking the rock into pieces.
Map digitization involves the extraction of data values from graph. It involves importing the graph from a file, defining the axis system and digitizing it automatically or manually
(i) Land surveying : This is the process by which measurement of the land is made and then represent such measurement by tables,places or layout for specific purposes.
(ii) Map scanning : Exiting maps of various scales containing different types of information about the area of interest are scanned. The information of these maps can be fed into a G I S
(iii) Tabular data : This involves the use of speed data arranged in tables and such data are analyzed and processed by computer in order to generate useful information
(iv) Field investigation : Computerized information systems for data management may be needed during emergencies.
A data base is operational in this case
(i)Abrasion or corrasion – This is when large pieces of bedload material wear away the river banks and bed.
(ii)Attrition – This is when the bed load itself is eroded when sediment particles knock against the bed or each other and break, becoming more rounded and smaller.
(iii)Hydraulic Action – This is when the force of water erodes softer rock.