Arbroath (Brothock Water) Flood Protection Scheme

Inundation plans

Flood events are referred to in terms of their Annual Exceedance Probability (AEP). The AEP is a measure of the likelihood that a flood of a given magnitude will occur once or more within any given year. The AEP is expressed as either a “one in X” value (e.g. 1:200) or as a percentage (e.g. 1:200 equates to 0.5%).

The table below summarises the return periods discussed in this report, and the equivalent AEP of these events.

Return Period Annual Exceedance
Probability (AEP)
1 in 2 year (Q2) 50%
1 in 5 year (Q5) 20%
1 in 20 year (Q20) 5%
1 in 100 year (Q100) 1%
1 in 200 year (Q200) 0.5%
1 in 500 year (Q500) 0.2%
1 in 1000 year (Q1000) 0.1%

Brothock Meadows

Hercules Den

St Vigeans