The Country Similarity Index attempts to quantify how similar countries are to each other relative to other countries. The index is a statistically-based way to measure this. 20% of the index is based on geography. 10% of a country’s geography score (2% of the overall Country Similarity Index score) is allocated for the country’s hydrology. The following are the factors that were included:
Freshwater Area
Two countries in the Great Rift Valley, Malawi and Uganda, have a large percentage of are their territory covered by freshwater lakes. Many Northern countries, like Canada, Sweden, and Finland, have a lot of their territory covered by freshwater lakes as well, due to glaciers creating them. Countries in the desert obviously have a low percentage of surface freshwater.
The Organization for Economic Co-operation and Development was the source of the information:
https://stats.oecd.org/Index.aspx?DataSetCode=SURFACE_WATER
Countries were categorized by the percentage of freshwater area:
0-.5%, .5-1%, 1-2%, 2-3%, 3-5%, 5-7%, 7-10%, 10-13%, 13-18%, 18-23%
(Permanent Water + (.5) Seasonal Water + (.5) Wetlands)
Coastal Borders
Island countries are completely surrounded by water, while landlocked countries have no coastline. For countries that are neither landlocked or islands, this section determines what percentage of the country is surrounded by land borders vs. coastline. Other than islands, some of the countries most surrounded by water include peninsulas like Denmark, Qatar, and South Korea.
Reddit was the source of the information:
https://www.reddit.com/r/MapPorn/comments/8vus19/rate_of_coastline_over_total_border_length/
Countries were categorized by the rate of coastline to total border length:
0-20%, 20-40%, 40-60%, 60-80%, 80-100%
Land Near Coast
While a country like Australia is completely surrounded by water, most of its territory is far from the coast. In addition, Canada technically has a the most coastline of any country, but only a small amount of its land is 100 km from the coast. In contrast, all of Brunei’s land is within 100 km of the coast, despite the fact that it is mostly surrounded by land borders, not water.
The University of Portland was the source of the information:
https://www.pdx.edu/econ/country-geography-data
Countries were categorized by the percentage of land at least 100 km from the coast:
0-20%, 20-40%, 40-60%, 60-80%, 80-100%