Climatology and Its Importance in Stormwater Design
Climatology is the science that studies long-term climate patterns that shape our environment. Unlike weather, which changes from minute to minute (today’s rainfall, wind, or temperature), climatology analyzes decades of data to reveal reliable trends.
In the field of applied hydrology and stormwater infrastructure design, climatology is essential. It provides the statistical basis to calculate design storms, assess flood risks, and ensure that systems meet regulatory standards.
Weather vs. Climate: The Key Difference
Weather: the short-term state of the atmosphere (e.g., today’s rainfall).
Climate: the statistical average of weather over 30 years or more.
For engineers, climate data smooths out daily variability and provides solid baselines, so that designs are based on science rather than guesswork.
Why Climatology Matters for Stormwater Design
Four major reasons stand out:
Predicting flood risks.
Sizing stormwater infrastructure (pipes, detention ponds, infiltration systems).
Meeting compliance and safety standards.
Supporting urban flood risk management.
Climatology translates scientific data into engineering decisions that protect communities.
Key Climate Variables in Hydrology
1. Precipitation
Rainfall is the driving force behind runoff. Engineers depend on intensity, duration, and frequency (IDF) statistics to generate hydrographs and define design storms.
Example: the 100-year, 24-hour storm is derived directly from climatology rainfall data.
2. Temperature
Temperature influences water movement:
In cold climates: controls snow accumulation and melt, leading to spring flooding.
In warm climates: accelerates evaporation and affects soil moisture.
3. Evaporation and Evapotranspiration (ET)
Evaporation: direct water-to-atmosphere transfer.
Transpiration: water loss from plants.
ET combined: a key variable in long-term hydrologic simulations and water balance studies.
4. Secondary Factors
Wind, humidity, pressure, and solar radiation also affect evaporation and runoff, and are included in advanced climate models.
How SWMM Uses Climate Data
The EPA SWMM model relies on climate inputs:
Rainfall time series: drive simulations.
Evaporation: affects continuous water balance.
Temperature: controls snowmelt and seasonal variability.
Advanced options: allow SWMM to read climate files with evaporation and wind speed.
These features let engineers replicate local conditions and improve modeling accuracy.
Sources of Climate Data
United States: NOAA provides Climate Data Online and U.S. Climate Normals.
Global: NASA maintains international climatology databases for engineers and researchers.
Conclusion
Climatology is the foundation of stormwater design. By understanding rainfall, temperature, and evaporation patterns, engineers can design drainage systems that protect communities from flooding and ensure compliance.
At Clear Creek Solutions, we offer free resources, including a basic EPA SWMM video course with 24 lessons to help you learn the software step by step.
