Using Buffer feature in QGIS

GO TO THE BLOG 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.


Go to Vector > Geoprocessing Tools > Buffer(s)


In the Buffer 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


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


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.


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.



Thank you for viewing the presentation.