Author: David Moravec
Cities are getting hotter. As concrete, asphalt, and dense apartment blocks increasingly replace natural areas, urban areas often heat up significantly more than surrounding rural zones in hot weather. This phenomenon — known as the “urban heat island” — isn’t just about discomfort: it can affect public health, energy demand, and overall livability. Our study offers valuable insight into how different elements of the urban landscape — rivers, lakes, vegetation, building density and height — interplay to influence the surface temperature of a city.
What Did the Study Look At?
We focused on Prague — a compact European city with a mix of dense urban areas, water bodies and green space. Using thermal data from the Landsat-8 satellite for summer 2022, we mapped surface temperature patterns across a fine-scale grid (30 × 30 m). Then we compared how four factors affected the land surface temperature (LST):
- Vegetation cover, approximated by the Normalized Difference Vegetation Index (NDVI) — a remote-sensing measure of “greenness.”
- Proximity to blue bodies: either rivers or large lakes.
- Building coverage (BC) — how much of the ground is covered by buildings.
- Building height (BH).
Using multiple regression analysis, we teased apart the relative influence of each factor on surface temperature.
Key Findings: What Actually Cools — and What Doesn’t
- Vegetation (green spaces) has the strongest cooling effect. Areas with higher NDVI — meaning more or healthier vegetation — showed significantly lower surface temperatures.
- Rivers help — but lakes don’t, at least not here. Being within ~200 m of a river was associated with cooler surface temperatures. Surprisingly, proximity to lakes had little to no significant cooling effect.
- Building coverage warms the city — a lot. The more ground is covered by buildings (impervious surfaces), the more the surface warms. The effect grows as urban areas become more compact.
- Building height matters little. In this setting, taller buildings (BH) showed only a small effect, much less than building density or green cover.
Why This Matters — for Cities, Planning, and Climate Action
This study highlights that if our goal is to cool down cities — especially in the face of climate change — investing in live, dense urban greenery pays off. In a compact city like Prague (and many other European cities), green spaces appear to be far more effective at reducing surface temperatures than relying on nearby small water bodies. Even the river helps only locally.
For urban planners and policymakers: the evidence suggests that mitigating urban heat is not just a matter of preserving water bodies or building higher — but balancing building density with ample, healthy greenery. Vertical development (taller buildings) may help limit sprawl and preserve open spaces, but without enough green infrastructure, heat will remain a problem.
For city dwellers: living near parks, tree-lined streets, or other vegetated zones likely translates into cooler and more comfortable local microclimates — especially important during hot summers.
Original Paper:
Kirschner, V.; Moravec, D.; Macků, K.; Kozhoridze, G.; Komárek, J. Comparing the Effects of Green and Blue Bodies and Urban Morphology on Land Surface Temperatures Close to Rivers and Large Lakes. Land 2024, 13, 162. https://doi.org/10.3390/land13020162