This is a “magic number” that is calculated by Dayboro Weather station, the weather station is located just up the hill from there and information collected is used to calculate the value.
How is the FBRFI index calculated?
It is generally based upon rain storms, a rain storm is:
Rain Storm is the rain total of the last rain event. It takes two tips of the rain bucket (which is a little gadget that measures the rainfall) to begin a storm event and 24 hours without rain to end a storm event.
Each rain storm is measured by the total amount of rain it produces, we then start looking at the ground saturation. The ground saturation is also a “magic number”. We use it to determine how much water can be absorbed (like a sponge really) we measure this at 10cm depth and 60cm depth.
Once we have created the “magic number” for the rain storm and the ground saturation we look at the rain fall in the past months, the rainfall in the past few months gives us an idea of how full the farm dams might be. You guessed it… another “magic number”.
By now we have a whole lot of “magic numbers”, using those we create an index, which in return is ……… Yup…. A MAGIC NUMBER.
Well you still with us… so that is good. That “magic number” is our flood index…. which ranges from 0 up to 90 or above… if it is above 90…. well at that point you are to late to buy a boat. (I guess that is why you see so many boats on trailers in this area….. people are prepared).
How serious is this?
Well as serious you want it to be. We have put a little bit of science in it, based the index on rainfall dating back to 2004. These numbers are depending on what is happening up stream, and how many new farm dams are established, how much road is been sealed, how many sheds are build, how many houses are build, how many tanks are installed….. you get the picture.
Anything that influences the water run-off will impact the “magic number”.
So use it as a guide, some sort of indication. Your own experience is always the best, this index is just another “magic number” you can use as a “marker”.
Dayboroweather.com (Lyndhurst-hill weather station) was the first to create “successful” automatic flood index measurements for Moreton Bay, since 2010.