NIMH

National Institute of Meteorology and Hydrology

Department of Hydrology, Division of Hydroforecasts

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Flood Protection Practices in Bulgaria

Flood Protection Practices in Bulgaria

Introduction

Generally Bulgaria is situated in the semi-arid zone under the mixed continental and Mediterranean climate influence. Floods are generated on the Bulgarian territory under the following conditions:

  • Intensive snowmelt mixws with rainfall at Springtime (this is usually the case at some Bulgarian tributaries of the Danube, e.g. Yantra and the plain regions in Northeast Bulgaria;
  • Flush floods caused by relatively isolated heavy rainfalls at Summertime (this happens often at some river basins in Southeast and South Bulgaria like the tributaries of Arda, Maritza and Veleka rivers, as well as at some Danube tributaries lika Yantra and Rusenski Lom rivers);
  • High flows with long duration which might affect the stability of the levees and subsequent flooding (this is an issue only along the Danube).

The flood protection practices in Bulgaria comprise range of activities, more or less intensive in different regions, depending on the level of flood hazard there.


Type of activities and division of work

There are a lot of different activities related to floods, undertaken by various institutions and NGOs. They coves both the short-term measures like flood forecasting and flood mitigation measures as well as long-term measures like prevention, legislation, infrastructure development, etc.

  1. Short-term measures include:
    • Flood monitoring and flood forecasting/warning, made by the National Institute of Meteorology and Hydrology.
    • In case of floods, flood mitigation and flood handling measures are:
      • Planed by the Civil ProtectionAgency
      • Implemented by the local municipalities and Civil Protection Agency staff, in case of catastrophic flood, Police and Army forces as well as other resources are involved
      • Coordinated by the Permanent State Commission for Civil Protection against Accidents and Disasters.
  2. Long term measures include:
    • Evaluation of the short term measures taken during flood periods, planning development activities, exercises, training, etc. This is mainly in the hands of the Civil Protection Agency and the local municipalities.
    • Regular inspection and maintenance of flood protection facilities like levees, protection walls, retention reservoirs, cleaning river channels, bridges, etc. This work is coordinated at present by the Permanent State Commission for Civil Protection against Accidents and Disasters. The role of the newly established Basin Authorities at the Ministry of Environment and Waters should significantly increase according to the new Water Law.
    • Issuing building permits, regulations, etc. Here the local municipalities and the newly established Basin Authorities at the Ministry of Environment and Waters are involved.
  3. Flood monitoring and forecasting/warning

    Real time monitoring and collection of hydrological data is implemented by the National Institute of Meteorology and Hydrology. Most of the river cross-sections are monitored by observers through foot gauges and report water levels via telephone or telegraph. From the existing 210-river level measuring stations, 44 are reporting at real or semi real time. Daily data collection ir arranged for 12 of those 44 stations, while for the rest a weekly cycle of daily values for the past week is arranged. The stations and the frequency of data collection for the Danube region is given in the table below:

    Table 1. Operational data used for flood forecasting services and transmitted operationally to the Romanian side.

     Station No.

     River

     Cross-section

     Data collection

     42070

     r. Danube

     Novo selo

     daily

     42073

     r. Danube

     Lom

     daily

     42075

     r. Danube

     Oryahovo

     daily

     42078

     r. Danube

     Svishtov

     daily

     42080

     r. Danube

     Rousse

     daily

     42083

     r. Danube

     Silistra

     daily

     16850

     r. Ogosta

     Misia

     daily

     18850

     r. Uskar

     Orehovitza

     daily

     21800

     r. Vit

     Tarnene

     weekly

     22800

     r. Osam

     Izgrev

     weekly

     23850

     r. Yantra

     Karantzi

     daily

     31830

     r. Rusenski Lom

     Bojichen

     weekly

    The nearest plans of NIMH are to equip 2-3 river level gauges at the most important Bulgarian tributaries of the river Danube with automatic telemetric facilities. Thus the input from the Bulgarian side will be elucidated by real time hourly data during floods. 9 of the river stations, located at Struma and Maritza river basins (South Bulgaria), are equipped by automatic river level gauges. Telemetric data transmission facilities are in operation at 4 of them, (as a result of Med-Hycos, WMO-World Bank project). NIMH is going to increase this number soon. For the above stations NIMH has computerized forecasting models able to give 24 hours lead-time flood forecasts.

    As national hydrometeorological service NIMH has framework agreements for real time data and flood forecasts/warnings exchange with relevant organizations as follows:

    • Greece under the PHARE and INTREG II, flood forecasting/warning system is maintained for the Struma river basin. That is under the cooperation agreement between the Bulgarian Ministry of Regional Development and Public Works and the Greek Ministry of Economy;
    • Turkey framework agreement between NIMH and DSI was adopted for data exchange and flood forecasting/warning for river Maritza. Project applications for further developments in the frame of some NATO programs are under preparation;
    • Romania under the umbrella of the World Meteorological Organization an agreement was signed in October 2001 for real time and flood forecasts/warnings exchange. The stations and the frequency of data which Bulgaria receives from Romania is given in the table below.

    Table 2. Operational data used for flood forecasting services and received operationally from the Romanian side.

     River

     Cross-section

     Frequency

     Data type

     Danube

     Corabia

     Daily

     levels/discharges

     Danube

     Tr. Magurele

     Daily

     levels/discharges

     Danube

     Giurdjiu

     Daily

     levels/discharges

     Danube

     Oltenita

     Daily

     levels/discharges

     Iron Gate 1

     Orsova

     Daily

     Levels

     Iron Gates 1 & 2

     n/a

     daily evacuated discharges

     Iron Gates 1 & 2

     n/a

     3 days forecast of daily evacuated disch.

     Iron Gates 1 & 2

     n/a

     3 days forecast of daily incoming disch.

     Jiu

     Podari

     Daily

     levels/discharges

     Arges

     Budesti

     Daily

     levels/discharges

     

    Similar set of real time data Bulgaria is making available to the Romanian partner. The list of stations and transition frequency is given in table 1.

    The operational issue of reports and forecasts is made in the Hydrological Forecasting Division, part of Hydrology Department of NIMH. The forecasts are based on:

    • Operational observations of river levels and provisional rating curves for real time translations of levels into discharges;
    • Operational synoptic meteorological forecasts of precipitation and air temperature;
    • Operational forecasts of precipitation and air temperature coming from the High Resolution Limited Area meteorological forecasting model (ALADIN).

    Most of the data processing work and calculations needed to issue the forecasts are computerized with relevant user interface and graphical visualization of the results. The evaluation of the forecasts and the issue of flood warnings are made by qualified engineer hydrologists. To improve further the accuracy and increase the lead time of the forecasts NIMH needs:

    • More sophisticated snowmelt/rainfall-runoff and routing models giving a possibility to use in detail the spatial variability of the runoff formation factors in the Bulgarian mountain landscape.
    • Precise cross-section information and DTM, to allow calculating the flood risk at any location of the river lowland, determine alarm and danger levels at sensitive locations and predict flooded areas and flood levels.
    • Real time automatic telemetric hydrometeorological stations, high resolution satellite data giving a possibility for operational analysis of the temperature and precipitation fields.
    • More accurate air temperature and precipitation forecasting by non-hydrostatic Limited Area High Resolution Meteorological models.

    The dissemination of the forecasts is restricted to the NIMH clients and permanent users, while the warnings go free to the government bodies and especially the Civil Protection Agency, the Ministry of Environment and Waters and especially to the press.