...
In the dynamic reporting point generation algorithm, from EFAS v5 and GloFAS v4 we only consider cells with an upstream drainage area above 1000 km2 for GloFAS, and 500km2 for EFAS, so cells with very small size drainage areas can not become reporting points. In the following, the reporting point generation is demonstrated on this small idealised river network area.
...
Next step is to compute the flood threshold exceedance values. CEMS-Flood primarily uses three main flood severity levels, the 2-year, 5-year and 20-year return periods. We determine for each of these
thresholds whether the predicted 30-day maximum river discharge in the ensemble forecast members (the control member and the 50 perturbed members) exceed exceeds the threshold value. We assign 1 if they exceed and 0 if they do not. This process is represented in Figure 2 by the coloured river cells, which show that the 30-day maximum river discharge exceeds the flood thresholds. Please note the triviality that if the 20-year threshold is exceeded for any cell, than both the 5-year and 2-year must be also exceeded for those cells, i.e. more and more cells are coloured (indicating exceedance), as we go from 20-year to 2-year level.
...
The fixed reporting points will always appear in CEMS-Flood (Figure 5a). They will be shown by one of the three colours, yellow, red and purple, representing the three flood severity levels. This level comes from the combined probability map, generated in the previous step (i.e. the map shown as 'Flood summary for days 1-30' on the GloFAS website). This means, whichever (highest) of the three severity levels is exceeded by at least 30% will define the colour of the fixed reporting points (if none of the severity levels are exceeded the points are shown in grey). In our examples one of the points will remain grey (i.e. below 30% 2-year probability, so no flood) and the other will be shown as purple (20-year flood level).
...
The removal of the pre-selected dynamic points is done using the so-called kill-zone (Figure 6d). This is a short river section both upstream and downstream (5 cells both directions) from either the fixed points or yesterday's dynamic points. The kill-zone is represented by light grey colouring in Figure 6d. The kill-zone only covers the main river channel and does not extent into the tributaries. It stops at the confluence cell when two relatively similar (in drainage area size) rivers meet. This is the case for the purple fixed point going downstream in the top-middle map and the yellow yesterday's dynamic points going downstream in the top-right map in Figure 6d. In case a bigger and a smaller rivers meet, like when going upstream from yesterday's yellow dynamic point in the top-right map in Figure 6d, the kill-zone will not stop at the confluence.
...