What is our community’s flood risk?
So Lafayette’s flood risk is increasing. Why? On the whole, because we’re seeing higher volumes of rain draining in an increasingly populated watershed.
Flooding in Lafayette Parish has essentially two sources: riverine floods caused by backed up channels and pluvial flooding, more commonly called flash flooding.
Riverine flooding happens when runoff builds up and water overtops the banks of rivers and streams. Water will often pool on roads, swell in coulees and spill over ditches. Your risk of riverine flooding is determined by how close you are to the river or major channel.
Lafayette’s exposure to it in major storms is documented in the well-known flood maps published by FEMA.
Don’t let the name fool you. In Lafayette, riverine flooding mostly affects homes and structures along the major coulees that feed the Vermilion River, not necessarily along the banks of the river itself.
Storm Intensity
Storm intensity is measured by rainfall over time. In Lafayette, 4 inches of rain in two hours is a 10-year storm, which has a 10% chance of occurring each year. But those odds add up over time.
| Storm | Annual Odds | 30-year Odds |
|---|---|---|
| 10-year | 10% | 96% |
| 25-year | 4% | 71% |
| 100-year | 1% | 26% |
| 500-year | 0.2% | 6% |
Pluvial flooding, also called flash flooding, is caused by intense bursts of rain that overwhelm the parish’s drainage system as quickly as it falls. It’s a somewhat hidden risk in Lafayette because it isn’t included on FEMA’s flood maps.
But it can be a substantial threat to communities with widespread development and relatively flat topography, like ours, making a smaller scale storm more likely to cause flooding.
Lafayette has seen a lot of those in recent years. Think of the July 2019 storm that caught usually flood-resistant parts of town by surprise, or the May 2021 storm that caught dozens of cars on flooded roads during the evening rush hour.
Even the recent Dec. 1 storm, which was on the weaker side of a 5-year event, caused problems in areas like Downtown, which is particularly vulnerable to flash flooding even though it isn’t in a FEMA flood zone.
The map to the right compares FEMA’s 500-year flood zone to a 500-year floodplain that also includes pluvial flooding modeled by UL’s Louisiana Watershed Flood Center, showing just how much of Lafayette’s flood risk slips below the radar.
See UL’s standalone 500-year flood map here.
Lafayette has grown in ways that have exacerbated our community’s vulnerability to flooding. Between 2001 and 2021, nearly half of new development in Lafayette Parish occurred within UL’s 500-year flood zone, greatly adding to the community’s flood risk.
Find Out More
The Current takes Lafayette’s issues seriously, and flooding is frequently top of mind in how we report on our community. Check out our coverage below to find out more about Lafayette’s flood risk, how it impacts us and what we’re doing about it.
Our Coverage
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