Bulgarian approach for preliminary flood risk

assessmentAssoc. Prof. Daniela Zlatunova

Sofia University “St. Kliment Ohridski”

Requirements of Flood Directive

• 1. Member States shall, for each river basin district, or unit of management, or the portion of an international river basin district lying within their territory, undertake a preliminary flood risk assessment .

Requirements of Flood Directive

• 2. Based on available or readily derivable information, such as records and studies on long term developments, in particular impacts of climate change on the occurrence of floods, a preliminary flood risk assessment shall be undertaken to provide an assessment of potential risks. The assessment shall include at least the following:

Requirements of Flood Directive

• a description of the floods which have occurred in the past and which had significant adverse impacts on human health, the environment, cultural heritage and economic activity and for which the likelihood of similar future events is still relevant, including their flood extent and conveyance routes and an assessment of the adverse impacts they have entailed;

Requirements of Flood Directive

• an assessment of the potential adverse consequences of future floods for human health, the environment, cultural heritage and economic activity

Approach used for preliminary flood risk assessment

Preliminary flood risk assessment based on the past flood

Preliminary flood risk assessment based on the past flood

• First step - a study of sources and create a chronology of historical floods

Preliminary flood risk assessment based on the past flood

• There are three cases of historical floods:– historical floods with verbal description of the

flood area;– Historical flood with mapped flood area;– Historical flood without information of the

flooded area;

Preliminary flood risk assessment based on the past flood

• I case - River Rositsa /town Sevlievo/ with verbal description of the flooded area

Outline the flooded are during the flood invent 1939 with Google Earth

Preliminary flood risk assessment based on the past flood

Georeferenced map of the flooded erea during the flood event 1939 – river Rositsa/town Sevlievo/

Preliminary flood risk assessment based on the past flood–

• Р. Марица – между гр. Пловдив и Първомай• Териториалният обхват на наводнението е

документиран на карта в мащаб 1: 250 000. Картата е съставена по данни, събирани на място, веднага след наводнението. Това ни дава основание да приемем, че тя с голяма степен на достоверност отразява действително залетите при наводнението през 1911 г.площи.

Preliminary flood risk assessment based on the past flood

II case - river Marica between town Plovdiv and town Purvomay with mapped area during the flood event 1911

Preliminary flood risk assessment based on the potencial/future/ flood

III case- river Aheloy - no information on flooded area in the past

Digital terrain model created based on SRTM- elevation data and river network (blue lines) in the lower reaches of the River Aheloy

Preliminary flood risk assessment based on the potencial/future/ flood

Preliminary flood risk assessment based on the potencial/future/ flood

• Calculating the maximum runoff

Preliminary flood risk assessment based on the potencial/future/ flood

• hydraulic calculations

Preliminary flood risk assessment based on the potencial/future/ flood

• Potential flooded area – river Aheloy

II.Analysis of the potential risk

• Four protected categories to assess the potential flood risk:- human health;- economic activity;- environment;- cultural heritage

II.Analysis of the potential risk- Criteria for analyzing flood risk:

• for human health and economic activity – “the number of affected people”;

II.Analysis of the potential risk- Criteria for analyzing the flood risk

• For environment;• Sources of pollution under Regulation № 166/2006,

European Community;• Protected areas according to Directive on the

conservation of natural habitats andof Wild Fauna and Flora/ Directive 92/43/EEC /and according to the Directive on conservation of wildbirds /79/409/EEC/;

• Protected water body under Article 119 of the Bulgarian Water Act.

II.Analysis of the potential risk- Criteria for analyzing flood risk

• For cultural heritage with:– category of "global importance" included in the

list of world cultural heritage;– category of "national importance" (archaeological,

historical, architectural and ethnographic objects and complexes);

II.Aproach for analysing of the potential risk

• Put together in GIS – the flood area, the area of settlements, industrial and natural protection areas an so on….

Aproach for analysing of the potential risk

III. Identification of the significant flood risk

• Criteria for significant flood risk:- number of affected people

/more then 15 affected people for the past flood and more then 100 affected people for the future flood/;

III. Identification of the significant flood risk

• I case – river Rositsa/town Sevlievo/ - 2 976 potentially affected people;

III. Identification of the significant flood risk

II case – river Maritsa

III. Identification of the significant flood risk

• III case – river Aheloy– No affected people

River sections with significant flood risk

Thank you !