Wang, L., Saiz, A. & Li, W. Natural fragmentation increases urban density but impedes transportation and city growth worldwide. Nat Cities

Objective:

• There is still relatively scarce research providing holistic, global and comparative understanding of the role of natural barries on urban outcomes

Case:

• Port cities

Methodology:

• Share of barries index
• Average nonconvexity index
• Detour index
• Robustness
  • change radius
  • data triming

Data Source

• People-based
  • Global human settlement urban centres database: GHS-UCDB
• Building-based
  • Spatial expansion of 200 cities: AUE
  • Urban areas: GHUB
  • Multitemporal global urban boundary: GUB
• Water bodies: Water Body Multitemporal
• Slopes: NASA Shuttle Radar Topographic Mission (SRTM)

Findings:

• Cities with a high share of barriers are predominantly situated in Central, East and Southeast Asia, and Southern Europe

• Most cities impacted by geographical barriers lay near the ocean

• Geographical constraints have an impact on road distances between points; however, barriers that generate nonconvexities display strong effects
• Dry places with no rivers and low precipitation tend to feature shorter-distance road trips
• Road distance tends to be lower in high-income countries

• A move across the 50th-90th percentile in barriers is associated with 14.5% higher urban densities, it’s also related with a reduced built-up imprint as a percentage of the urban area
• Geographical fragmentation in and around cities to be associated with lower GDP per capita
• Topographical land fragmentation is associated with reduced urban night lights

Coding Reference:

• Stata and Python