Elements of simplified methodology for preparation of flood maps

For the flood hazard maps the simplified methodology proposes classification of hazards according to the flood depth:
Class Class delimitation
Depth (m)
1 < 0.25
2 0.25 - 0.5
3 0.5 - 0.75
4 0.75 - 1
In accordance with the Program the simplified methodology proposes the following categories of risk receptors:
  • Indicative population;
  • Economic activities;
  • Environment;
  • Cultural-historic heritage. 
Each of the listed category contains its subcategories, which are further divided into specific groups. The degree of division and the final list of all risk receptors will be determined during the development of risk maps, depending on the spatial analysis of data and the obtained risk assessment results.
 
For development of the flood risk maps the simplified methodology proposes use of "risk module", which represents the sum of risk receptors, in order to quantify each risk receptor in a unique way over the value of its module, regardless of its dimension (number, m, m2).
 
The impact of the flood hazard to the increase of flood risk according to this methodology is expressed by the flood depth defined by the hazard maps. The flood risk for each of the categories of the receptors would be expressed as a risk factor, which is a product of a specific risk (vulnerability) and the flood depth (hazard).
 
For the purpose of mutual harmonization of hazard and risks maps, the following classification and visual interpretation of risk is proposed:
Class Risk
Class delimitation
 
1  small risk < 0.25
2  medium risk 0.25 - 0.5
3  high risk 0.5 - 0.75
4  extreme risk 0.75 - 1
Basic data representing flood risk maps are obtained as a product of value for hazards (depths) and endangered/receptor categories.
 
According to the proposed methodology, which was used during first planning cycle, flood risk maps will show potential harmful consequences linked to two flood scenarios (middle and low) in relation to the flood receptors, and other useful information. Flood risk maps defined in such a way will not follow the usual definitions of risk (combination of probability and effects of the flood event), but will show flooding of risk receptors in the defined scenarios. In this simplified manner, the information should be easier to understand, not only for the experts in this field, but also the wider public.
 
This proposal of elements for development of a joint methodology for preparation of flood maps in the Sava River Basin can serve as the starting point for future improvements and enhancements if there still would be a need to use such a methodology for a purpose of joint activities.