In a couple of works along the CCDR (Caribbean) we got asked to:
express the individual risks score into some combined metric;
rank the risk in a way that is comparable with other countries of future periods (i.e. a risk growing from "medium" today to "high" in the future).
For option 1, we thought of this:
Consider the EAI or EAE, both as absolute and % over total, for each exposure category within an hazard (e.g. FL_Pop_EAI, FL_Pop_EAI%, FL_Builtup_EAI, FL_Builtup_EAI%, FL_Crops_EAE, FL_Crops_EAE%)
Normalise 0-1 each of the column using max and min (excluding zeros)
Calculate the GEOMEAN between the normalised scores: we obtain a new score 0-1 indicating the intra-country risk ranking for each hazard (actually using the double-inverse GEOMEAN calculation to make it conservative towards the max).
In the same way, we calculate the geomean of each hazard normalised score to produce a general risk ranking.
This ranking is only useful to set priorities within a country. In this sense, "low" risk score wouldn't necessarily mean that that is low in absolute terms. The same non-normalised value could correspond to "high" risk in another country.
This is also not useful if you want to compare to the future of the same country, as the future scores would be again normalised 0-1 (i.e. can't turn the amp to 11).
To tackle this, after discussion with OECS people, I came out in extremis with option 2: which is simply expert based thresholds for each hazard, only accounting for the relative value (EAI% and EAE%). Each hazardXexposure has its own threshold, purely expert based, accounting both for the data distribution and general rules of thumb (generalisation potential). The individual scores are not combined. I reckon this is very sensitive to ADM size, i.e. an EAI=50% could correspond to 1 people in some unit, and to 10,000 in another unit.
But I hadn't the chance to think too much - also I'm very much over the agreed contract time.
Any suggestion is welcome, as I feel it won't be the last time we get this kind of requests.
In a couple of works along the CCDR (Caribbean) we got asked to:
For option 1, we thought of this:
This ranking is only useful to set priorities within a country. In this sense, "low" risk score wouldn't necessarily mean that that is low in absolute terms. The same non-normalised value could correspond to "high" risk in another country. This is also not useful if you want to compare to the future of the same country, as the future scores would be again normalised 0-1 (i.e. can't turn the amp to 11).
To tackle this, after discussion with OECS people, I came out in extremis with option 2: which is simply expert based thresholds for each hazard, only accounting for the relative value (EAI% and EAE%). Each hazardXexposure has its own threshold, purely expert based, accounting both for the data distribution and general rules of thumb (generalisation potential). The individual scores are not combined. I reckon this is very sensitive to ADM size, i.e. an EAI=50% could correspond to 1 people in some unit, and to 10,000 in another unit.
But I hadn't the chance to think too much - also I'm very much over the agreed contract time.
Any suggestion is welcome, as I feel it won't be the last time we get this kind of requests.