Lab 7 - Coastal Flooding

This week's lab focused on mapping sea level rise and quantifying the effects it would have on local populations.

Projected 6 ft. Sea Level Rise in Honolulu, Hawaii

The above map shows what a projected 6 foot sea level rise would mean for a small section of coastline within Honolulu, Hawaii. The inundation area is overlaid on top of the current population density per census tract area. As shown above, quite a bit of the currently populated sections of Honolulu would be impacted.

The flood zone area was created by subtracting the total sea level rise from a DEM using the Less Than tool (values were converted from feet to meters, so 2.33 m was subtracted from each cell of the DEM - which contains elevation values). Each DEM cell area is 3 m x 3 m - so each cell covers a 9 m square area.

The resulting raster data created by using the Less Than tool were converted to a vector format using the Raster to Polygon tool. This data was then displayed on top of another raster showing total depth within the flooded areas (created also from the source DEM using the Extract by Attributes and Minus tools) and the population density data. The flood layer has been set to a 50% transparency to allow for viewing of the layers below it.

Additional demographic analysis was completed using 2010 U. S. Census data. Three variables were tracked within the flooded vs. non-flooded areas: total white population, total home owner population, and total population of persons 65 and older. Of the three demographics, the most directly affected are the home owners who represent half of the total population and are the hardest hit percentage-wise under the 6 ft. sea level rise scenario. The least affected are those who are 65 and older - these individuals represent only about 18% of the entire District of Honolulu population and less than a quarter of this population is within the area of projected sea level rise.