How we made these images....
Were wondering how these images were made ? Well this page explains where the data come from and how they were used to make the images on the other pages.
Landsat Imagery
The satellite data used to show the features of the island of Oahu is Landsat imagery downloaded from the Hawaii State GIS Program web site. The image below shows what the raw data from the site looks like.
We took the raw data and masked out the sections containing water (both near shore and off shore) so we could show the bathymetry around the island. The resulting masked image looks like the picture below.
USGS Digital Elevation Model (DEM)
The elevation model for Oahu used to calculate the different steps for sea level rise was downloaded from the USGS Hawaii Data Clearinghouse. The data has an elevation point every 10 meters (about every 32 feet) for the entire island. The picture below shows a representation of the data as if it were illuminated by the sun from the north.
Multibeam Bathymetry
The University of Hawaii has been processing bathymetry, or water deptg at a given location, for the entire state of Hawaii. The compilation includes data collected by many platforms including a large amount from the University's research vessel the R/V Kilo Moana. The image below shows the coverage of multibeam data around Hawaii. For our sea level simulation the bathymetry was used as a backdrop to make the images look more complete.
Put It All Together (How we calculate the sea level rise for the island).
In order to calculate how far the ocean would intrude as sea level rises use a computer program to determine what sections of the island would remain above sea level and other sections that would fall below. The example below illustrates current sea level. All area shown in blue are below sea level while areas shown in green are above sea level.
The next image illustrate a second case where sea level has risen 70 meters . The blue plane (ocean) now covers much of the former coastal zones of the island. The former coastline is shown in silver. Only the peaks of the Koolaus and Waianes and the high plateau between them poke out of the water.
There are some problems with this type of approach. The biggest problem is that we trust the digital elevation of the island to be correct., but this particular DEM represents some regions as lower than they actually are. With higher quality DEMs it would be possible to more accurately model the ocean intrusion on Oahu.