09/11/2025
In the course of our quest to reduce flood and restore forests, we noticed many people believe that we cannot calculate the amount of water we need to manage during storms, and thus cannot accurately prepare for them. This is a continuation. of our previous post on mm/hour of rain - how much water do our cities and towns actually absorb?
Absorptive capacity of water of different land surfaces: (flat land with 0 slope)
Standard Concrete/Asphalt: 1mm/hour/sqm
Compacted Soil: 3mm/hour/sqm
Grass: 10mm/hour/sqm
Small/Young Forest/Woodland Park: 50mm/hour/sqm
Old Growth Forest: +300mm/hour/sqm
Our team prepared this information in hopes that we can all take steps towards managing flood water. This is especially important to those who influence space: engineers, architects, governments, land owners and developers - those who directly or indirectly decide what our land surface will look like.
They can use this to calculate the safe amount of concrete/earth/grass/forest in a space, town, city or province, assuming that today’s storms will be like Tino and Uwan who bring +200mm of rain in 24 hours or less.
Let's plant trees, but we are also asking for help to share more sustainability math like this with grade school, high school and college systems so that everyone understands the effects of climate change, and how we can build a country that's prepared for it.
Thank you to all who have helped us (especially ) plant over 100,000 trees since 2016. Send us a message if you want to get involved, want more information, or want to collaborate! Let's take care of nature, and our home planet.
*absorption rates will vary based on kind of soil, health of soil and size of plants. Slopes will also reduce water absorption rates
**information is based on research with several sources, including plantation farmers, FAO and other farming websites. Actual numbers may vary site to site but this gives you an indicator of how big the changes are from forest to concrete.
Please share info with relevant organizations and groups that influence the land in your hometown and the country :)