The Underappreciated Discipline: The Importance of Hydrology
By L. David Givler, MSCE, PE
What is Hydrology?
What’s hydrology all about, anyway? Some might think it’s a boring or overly complicated field of study. Others might not have any idea what it even entails.
According to the U.S. Geological Survey, “Hydrology is the science that encompasses the occurrence, distribution, movement, and properties of the waters of the Earth and their relationship with the environment within each phase of the hydrologic cycle.” Essentially, it’s the study of water in all its forms and how it interacts with the environment.
For civil engineers, hydrology is crucial. They focus on the aspects that allow them to calculate flood flows based on regional rainfall patterns, topography, soil conditions, and urban development. Civil engineers also apply hydraulics — the study of fluid mechanics — to predict how floodwaters move through natural streams, manmade channels, reservoirs, and floodplains.
Practical Applications of Hydrology
How Does Flood Mapping Work?
The recent floods of July 2025 highlight the critical importance of hydrology and hydraulics, particularly in floodplain planning. This aspect of the discipline is a matter of life and death.
No one understands flooding better than hydrologists. These professionals interpret charts, perform calculations, run models, and ultimately draw the lines that distinguish safe areas from flood hazard zones. While hydrologic principles can be complex, a well-crafted flood risk map should be clear and accessible to everyone.
Flood studies primarily aim to protect society from extreme events. Unfortunately, this essential work is often misunderstood or undervalued. Why? Because it frequently requires spending money or limiting land use to safeguard people and property from rare events that many have never witnessed.
On sunny days, when there’s no rain and everything seems fine, flood planning can feel irrelevant — even like a nuisance. But the day after a flood, when the devastation is evident, perspectives shift. Suddenly, everyone wonders why more flood studies weren’t conducted and why better safety measures weren’t implemented.
Why Are Flood Hazards Underestimated?
There are several reasons why people underestimate flood risks and the vital role of hydrologists:
1. Familiarity Bias
People who spend a lot of time on a property often believe they understand its flood risks better than they actually do. Most of their experiences are under normal, non-flood conditions, which become their standard of reference.
For instance, a family may have owned a property for generations. The current owner might think, “If this land has never flooded in all these years, why should I believe the hydrologist’s model suggesting otherwise?” This bias leads them to dismiss expert predictions, even though hydrologists rely on scientific data rather than anecdotal experience.
2. Climatic Influences
Local climate can also play a role in underestimating flood risks. In arid regions, streams might be dry 98% of the time. Without consulting a hydrologist, people might assume it’s safe to build in these low spots.
For example, one family decided to expand their home by adding a new wing across a dry creek bed. Without realizing it, they effectively turned their house into a dam. When the rains came, the creek flooded, and the water rose so high that they could see it through their kitchen windows. The damage to both the new addition and the original structure was extensive.
3. The Lure of Creekside Beauty
Aesthetics can sometimes overshadow practicality. Picturesque hollows or dry stream beds may seem like the perfect spot for a cozy cottage or campsite. However, the natural beauty of these areas can distract from the very real dangers of building in a floodplain.
4. Underestimating the Speed of Floods
Even when people acknowledge the risk of flooding, they often overestimate their ability to escape. They assume they’ll see or hear the floodwaters coming in time to act.
However, floods can rise shockingly fast. During the recent Guadalupe River floods, water levels reportedly rose nearly 13 feet in 15 minutes and 30 feet in one hour.
What’s more, floods often occur at night when people are sleeping. Imagine waking up to water in your bed, no power, and complete darkness. Navigating to safety under these conditions can be disorienting and dangerous.
5. Misunderstanding the Nature of Floods
Many assume that floods are simply excessive water flows that create drowning hazards. They believe that strong swimming skills are enough to stay safe.
In reality, floods are far more dangerous. They often carry massive amounts of debris — trees, vehicles, barbed wire fences, rocks, and more — that can crush or trap people. The speed and force of floodwaters can sweep people off their feet, drag them underwater, or turn debris into deadly projectiles.
What Does a Hydrologist Do?
Hydrologists Save Lives
To the hydrologists out there: your work is invaluable. When you carefully draw those flood boundaries and communicate risks effectively, you help save lives and protect communities.
Remember, even if your work feels unappreciated on sunny days, it becomes essential when the storms come. Keep doing your critical work — ensuring that people know where they’re at risk and where they can find safety.
