Using Buffer feature in QGIS

GO TO THE BLOG’S DEMO VIDEO PAGE AND WATCH THE YOUTUBE VIDEO DEMO

Task

The demonstration will simply show how to place a buffer zone around a  feature layer and the practical application of using GIS to estimate the effect of a flood when the dam water are released.

Steps

– Digitize the Dam and Lake as polygon features.

– Use Vector geoprocessing tool to place a buffer zone around the water body.

– Use openlayers to load the google satellite base map.

 

A polygon feature layer- dam is digitized. We intend to place a 0.0052dd buffer around it to assess and estimate the physical damage a flood plain of that size will cause.

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Go to Vector > Geoprocessing Tools > BufferSleeping half-moon(s)

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In the BufferSleeping half-moon window. Fill in the buffer distance (in the case of our demo, 0.0052dd) and take the default segments to approximate and set a destination for the file. Set ID as the Buffer distance field. Browse for a destination for the output shape file

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A buffer polygon layer is created around the Dam. See the layer in the Layers window.

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To complete the assessment , we need to add the satellite image of the area so as to ascertain the physical environment that falls within the buffer zone that was created.

Go to Web > Openlayer plugin > Google Maps > Google Satellite or you may choose any other web map service or engine of choice.An internet connection is required to do this download.

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The Google satellite image is then loaded in as a layer, an internet connection is required for the loading. The final map shows quite a sizeable number of houses and streets will be affected within the buffer zone. This map can then be given to ground assessment teams to guide their work.

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Thank you for viewing the presentation.

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