It is important that people understand what is meant by a 100 year flood plain. My dad was a civil engineer, I’ve seen him review 100 year flood plain maps as well as 500 year flood plain maps.
Many people use and misunderstand what is meant by 100 year flood plain
FEMA 100 year flood plain
100 year flood plain- a line that designates that statistically there is a 1% chance that a flood could occur within the boundary in any given year.
500 year flood plain- a line that designates that statistically there is a 0.2% chance that a flood could occur within the boundary in any given year.
The line of a 100 year flood is a designation based on a statistical analysis of hydrological information. It doesn’t mean only one will happen once in 100 years, nor does it mean 100 years will pass since the last 100 year flood.
The line of 100 year flood also does not have a depth of water, nor does it have a time of year, or a speed of movement.
This designation is used to determine types and locations of development and also costs of insurance for structures. The designation is not meant to be a hard predictor- it is meant to be a soft number for estimation.
What kinds of things change the 100 year flood plain?
When land development occurs upstream, flood events occur, dams are built or rebuilt, the lines of the 100 flood plain changes.
As the planet’s climate changes we must realize we will be less able to understand storm events, much less know or predict where and when storms events and floods will occur.
Is there a process to do review how land development upstream may impact the existing structures or flood plain status of land downstream? No
As investigations are taking place to determine how to prevent future loss of life during floods- answers will not include telling land owners they cannot build along the rivers.
Solutions
A solution would be to review emergency notifications and determine how they can be received by camp directors and counselors in a timely fashion, to they can escape on roads that are passable.
IMO
Heartbroken- We are about one week out, over 100 deaths, over 150 still missing.