Hydrology of a Flood
Water Storage
Greater urbanization, combined with global warming, has led to an increase in flooding and flash flooding. Paved streets, parking lots, driveways, sidewalks all have zero capacity to absorb precipitation, creating a surplus of water run off that can lead to dangerous flooding. USGS.gov Already brimming lakes, rivers, and streams serve as home to much of the precipitation that meets landfall; some being captured at the time of rainfall and some collected as runoff from excess ground water or melted snow. But as precipitation amounts rise, the capacity for these natural water basins to hold onto it decreases.
Rainfall Intensity & Duration
Rainfall intensity and duration are the two main factors that contribute to flooding. USGS.gov Flash flooding happens over a short period of time, where rainfall intensity is immense, like in a tropical storm or hurricane. These types of storms are generally fast moving, but bring with them significant amounts of precipitation, causing acute and unpredictable flash floods. Longer lasting, slow moving thunderstorms that hover over a particular area can bring with them mass amounts of precipitation. These types of heavy downpours cause flooding in rural, coastal and suburban-urban areas. With excess runoff from groundwater being unable to absorb into pavements it finds its way into the soil, which depending on the compounds of the soil, could be porous or not. The excess water may also find its way into already full rivers and streams, causing them to overflow into the embankments. Ocean tides are affected by extreme weather and the surge from high tides can decimate coastal regions. All this water overflow eventually finds its way into homes, school buildings, supermarkets, office buildings, underground trains and subways causing major damage.
Catchment Area
A Catchment, or watershed, “is an area of land that drains all the streams and rainfall to a common outlet.” USGS.gov Examples of this are bays, draining into oceans, or a muddy puddle depression in saturated soil that fills with excess run off water in its path. Some water flows deeper into the ground and, instead of flowing to rivers or streams, creates underground reservoirs called aquifers. Oceanservice.noaa.gov These catchment areas and aquifers collect rainfall and melted snow. When the excess runoff water is great, beyond the capacity of the watersheds and aquifers, that is when flooding occurs.
Flood Prevention
How do we compete with increased flooding? Preparedness. As our world continues to navigate the new normal of extreme weather events, specifically flooding, our best defense is to be ready for the storm. Garrison Systems and Garrison Flood Control offer a variety of flood diversion and prevention technology that is easy to use, quick to deploy, and stores compactly when not in use. As our long term efforts to reverse global warming slowly begin, we still must be prepared for the now. We can do that by readying ourselves with the right protective equipment. Contact us for more information and to speak with a flood specialist about your needs.
Sources
https://www.usgs.gov/special-topics/water-science-school/science/floods-things-know
https://www.usgs.gov/special-topics/water-science-school/science/watersheds-and-drainage-basins
https://oceanservice.noaa.gov/facts/watershed.html