GIS
Raster Application on Coastal Flood Hazard
Raster data is data that is stored in the form of a rectangular box
(grid) / cells to form a regular space. Digital photos like areal photography
or satellite imagery is part of raster data on a map. Raster data represents
the grid continue. Value using the color image photography, which show the
level of red, green, and blue in the cell. On raster data, the geographic
objects represented as a grid cell structure called a pixel (picture element).
Resolution (visual definition) depends on the pixel size, the smaller the size
of the Earth's surface is represented by the cell, the higher the resolution.
Raster data generated from remote sensing systems and very good to represent
the boundaries are changed gradually as soil type, soil moisture, temperature,
and others. Raster maps are maps obtained from an areal photography, satellite
images or photograph the earth's surface which is obtained from the computer.
Examples of raster maps taken from weather satellites.
Raster data can be applied to the measurement of coastal flooding.
Examples are tidal flooding in coastal areas. The phenomenon of flooding due to
tides (rob) has a negative impact on coastal residential areas. The impact of
flooding due to tides (rob) has changed the physical environment and the
pressure on the public, buildings, and infrastructure of existing settlements
in the region. Flooding due to tides (rob) will have an impact on environmental
damage to infrastructure (water, waste, drainage, sanitation) as well as a
marked decrease in environmental quality with lower quality of public health.
Raster data applications one of which is to determine the distribution of
flood inundation (rob) in a coastal area that was raised by sea level rise and
inundation identify the impact of flooding (rob) on settlements. Distribution
of tidal inundation mapping is done using digital data in raster format in the
form of a map DEM and map point heights. To find out areas that were flooded,
the data is also used in a tidal flood elevation coastal zones. Dioah the data
by the method of interpolation, overlay and iteration techniques. Preparation
of maps spread the distribution of tidal inundation was done by using iterative
calculation using a specific algorithm. The analysis conducted is the Digital
Elevation Model (DEM) or Digital Elevation Model is a visualization front
elevation topography or soil that is built based on the results of the
deterministic interpolation is made using the moving average method of
interpolation. Digital Elevation Model pixel size used was 50 m with a
precision of 1. Digital Elevation Model in a particular area shown in 5
classifications height values. Gradations of color in the Digital Elevation
Model present face value of the height of land in a coastal region. Formulation
of scenarios that simulated tidal flood elevation based on DEM data generating
tidal inundation area which covers a different value in each scenario. Scenario
inundation models created using several assumptions, such as the protection of coastal
buildings as embankment with a height of 180 cm. Based on the map, such as
tidal flood inundated areas in pairs of 2 m or 200 cm and 2.5 m or 250 cm,
whereas at a height of 100 cm and 150 cm inundation has not happened because
the embankment is made still able hinders the high tide sea water inundation.
References :
Marfai M.A. 2003.
“GIS modelling of river and tidal flood hazards in a waterfront city: case
study, Semarang City, Central Java, Indonesia”. Thesis, International
Institute for Geo-Information and Earth Observation, ITC, Enschede, The
Netherlands.
Putra, RD and Marfai M.A. 2012. Identifikasi Dampak Banjir Genangan (ROB)
terhadap Lingkungan Permukiman di Kecamatan Pademangan Jakarta Utara. Jurnal
Bumi Indonesia. Vol. 1 No.1. Yogyakarta.
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