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Case Study – Karlovac


In 1597 the ancient Croatian city of Karlovac was established by the Austrians in Karlovac County, as a fortress city for protection against Ottoman advances (Crljenko, 2013). The city was built near four rivers (Korana, Kupa, Mreznica and Dobra) as seen in Figure 1, all of which flow through or around the city and gave it its name of the City on Four Rivers (Druza, 2016). The strategic position of the city in relation to the rivers, played an integral part in its success as a defensive military position and trading center. During the Croatian Homeland War (1992-95), Karlovac was an important strategic location that endured heavy fighting and damage (N.A. 1991). Today, Karlovac is the ninth largest city in Croatia with a population of 52,488 out of a national population of 4,154,213  (Croatian Bureau of Statistics, 2016; World Population Review, 2018). Croatia joined the European Union (EU) in 2013. The national population of Croatia has been in decline primarily as a result of emigration to other countries within the EU. The Karlovac population mirrored this trend with an 11.96% decline between 2001 and 2016 (Croatian Bureau of Statistics, 2016). The impact of this movement has been felt as skilled and well qualified Croatians have moved abroad, reducing its capacity to effectively and timeously solve complex infrastructure and natural disaster challenges. Membership to the EU has not been without benefit. By doing so the country gained financial and economic aid, as well as access to expertise from various programs within the EU. The EU has numerous rules and regulations that all member countries must adhere to. One of these requirements is for member states to identify the most flood prone areas of their country. This requirement highlights the significant negative impacts flooding can have on a nation and the need to mitigate them.

River Map in Karlovac.jpgFigure 1. River Map in Karlovac (Source: Cvitan, 2017)



Figure 2. The City of Karlovac  in Croatia “Croatia Political Map” (Source: Ezilon cited in The Maritime Explorer)

The City of Karlovac is situated in the central continental part of Croatia in Karlovac county (Figure 2).  It is situated at the junction of the lowland and mountainous regions of Croatia in the “soft underbelly” of the central part of the country between Slovenia on the west and Bosnia and Hercegovina on the east. It is one of the rare cities in the world that sits at the confluence of four rivers: the Kupa, the Korana, the Dobra, and the Mrežnica. The city of encounter of four rivers is recognized as the perfect place to represent the abundance of life in Croatian rivers. With the support of the European Union, the first freshwater aquarium in Croatia – Aquatika – was opened next to the river Korana in 2016. In 25 pools imitating the bed of a karst river from its source to its mouth, there are five thousand specimens of fish belonging to a hundred fish species. (Karlovac City of Meetings, 2017).


In 2018 we undertook a field trip to Croatia to learn about the country’s hydrological challenges. This included a visit to Karlovac to investigate the responses to the flooding events they have been experiencing within the last 10 years. The goal of this project is to outline the causes of Karlovac’s flooding, the current and futures solutions, the sustainability of these solutions, and current and potential challenges for stakeholders.

The rivers provide the Karlovac citizens and tourists with access to drinking water, sanitation, irrigation, numerous recreation activities and are a key component of the cultural fabric of the city.  However, in recent years the rivers have become a cause of concern as Karlovac has experienced significant flooding events. These events have been increasing in both intensity and frequency. Some of the earliest floods in Karlovac occurred during the construction of the original star city in 1579. The First great flood experienced by the city occured in 1613, pusing residents and military personnel to live on higher levels of houses and barracks. Some historic records also mention floods in 1730, 1775, 1852, and 1895. (Cvitan, 2017) Significant floods were also recorded in 1939, 1966, 1972, 1974, 1996, 1998, 2001, 2005, 2010, 2012, 2013, 2015 and 2018 (Croatian Waters, 2013).

Karlovac is one of a few cities which historically has, and will continue to be, one of the Croatian inland areas frequently subject to flooding. Croatia was listed as being second only to Norway for the water resources per capita in 2002 (Gramatikov, 2009). The prevalence of hydro-geologic systems which have shaped the landscape continue to do so in a way which will also influence the behaviors of the region’s population.

“Flash floods are most likely to occur during the season of high intensity precipitation, from May to September, groundwater floods from November to March, flooding of poljes in karst from October to April. It is estimated that floods endanger over 15% of the national inland territory.” (Geres, 2009).

More recent flood events such as those in March 2018 have been the result of heavy snow precipitation followed by warm spring temperatures and heavy rains (Ilic, 2018).

Although Karlovac is a city built on the convergence of four rivers and historically has survived floods, the recent and increasing intensity of the floods are posing various challenges to the citizens and other stakeholders. Some of the challenges include the ability to effectively ensure the safety of the cities residents. The un-narrated rough cut video below shows the floods in the City of Karlovac in 2015 as it is inundated with rising water levels. Reuters reports that the water levels on two rivers rose to over 8 meters after days of heavy rains.

Escaping the flood waters in Croatia (Source: Reuters, 2015)

Click hyperlink to play or copy and paste:


Figure 3. Floods in Croatia – Karlovac. (Source: EMSR101: Copernicus; European Commission (2014)

The climate of central Europe, including Croatia has been warming for the past several decades and has increased in severity in the past 25 years (Croatian Meteorological and hydrological Service, 2009). According to the Croatian Meteorological and Hydrological Service  (2017);

“The average annual air temperature in Croatia was above the multi-annual average (1961 – 1990). Average annual air temperature anomalies were within the range from 0.6°C to 2.1°C. According to percentile ranks and classification ratings, thermal conditions in Croatia in 2017 dominantly fall into the extremely warm category, while the wider area of the town of Daruvar as well as parts of the Middle and Southern Adriatic fall into the very warm category. An analysis of annual precipitation amounts expressed as percentages (%) of the 1961 – 1990 average indicates that precipitation amounts in Croatia at most meteorological stations encompassed by the analysis were above the average.  A comparison with the multi-annual average reveals that the precipitation amounts in 2017 were within the range of 66% – 130% of the above average.”

This trend of increased temperatures and increased precipitation, especially when combined with heavy snowfall and warmer spring temperatures results in flooding in Karlovac and is expected to continue into the foreseeable future (Pavlić, Kovač, Jurlina, 2017)

Figure 4. Scale of the Flooded Area from 2010, 2013, 2014 and 2015 (Source: Cvitan, 2017)


Sector Motivation Influence

  • Tourism industry
  • Agriculture
  • Local businesses
  • Karlovac County Chamber of Commerce
  • Reduce negative economic impacts as a result of flooding. Including damage to and loss of assets and reduction in workforce capacity.
  • Improve Karlovac’s capital investment potential from both internal and external resources
  • Business growth
  • Ability to attract capital investment
  • Expertise in project management and engineering
  • Long term perspective aids in planning

  • Local emergency services
  • Military
  • Local mayor and city council
  • Karlovac County government
  • Croatian national government
  • Croatian waters
  • Croatian Meteorological and Hydrological Service
  • Croatian Department of Energy and Environmental Affairs
  • European Union
  • The local fire department are motivated to protect the properties and lives of  their fellow community members. This motivation is personal as they and people they know are directly at risk and impacted by the flooding.
  • Local government are interested in finding a solution as the more frequent and larger flooding events cost the town money and divert resources (human and capital) that could be used for other projects. They are also interested in limiting and potentially negative political impacts that could result from their constituents frustration with the response to flooding.
  • The local government wants to improve the economy of the area and its attractiveness as a place to live and visit.  This will improve their tax base.
  • Learn new technologies
  • National level agencies are motivated to mitigate flooding in order to alleviate political pressure from the citizens of Karlovac.
  • The ability of the fire department to create a sustainable long term solution to this problem is very limited. They do not have the expertise nor can they attract the required funding to develop and implement large scale long term infrastructure improvements.
  • The local government is limited in its ability to raise capital for large scale work and are dependent upon the national government and Croatian Waters for funding.  These two national entities are then largely dependent upon the EU for funding.
  • The national government and its water management agency have numbers competing priorities across the country for water related infrastructure projects.
  • The influence of government at all levels is negatively impacted by the emigration of skilled labor.
Civil Society

  • Local residents
  • Tourists
  • Media
  • NGO’s
  • Do not want homes and other assets damaged as a result of flooding (no meaningful insurance available).
  • Do not want to lose potential income through lost wages during flood events.
  • Flood mitigation actions reinforce appropriate use of funds, and involvement in EU programs signifying cooperation since becoming a EU member nation.
  • Can apply pressure on politicians to improve response to flooding.
  • Tourists can ‘vote’ with the dollars and feet by visiting alternate locations.
  • EU programs which seek to foster the sustainable development of developing countries within the union.

The need to mitigate flooding in and around Karlovac is a concern for the many local, regional, and national stakeholders. They have recognized that changes in hydrogeologic timing have altered enough to impact human activities to the point of requiring flood engineering interventions.

“If the trends in flood timing continue, considerable economic and environmental consequences may arise, because societies and ecosystems have adapted to the average within-year timing of floods. Later winter floods in catchments around the North Sea, for example, would lead to softer ground for spring farming operations, higher soil compaction, enhanced erosion, and direct crop damage, thereby reducing agricultural productivity” (Blosch et al., 2017)


Figure 5. Chief of the Karlovac City Fire Department giving a presentation to Virginia Tech Graduate students (Source: Belfield, 2018)

The extremes of too much water, as with hurricanes, tsunamis or floods, or too little, as with droughts or over-exploitation, present water security concerns. Scientists from the United States and Croatia recognized that water security is an important issue of common concern and that by sharing research and experience between themselves and with others in Europe, decision support related to water security would be advanced (Gramatikov, 2009). Stakeholders have recognized the necessity to intervene in the natural process, and inject human derived environmental engineering controls to mitigate flooding.

The Karlovac City  Fire Department is motivated to protect the properties and lives of  their fellow community members. This motivation is personal as they and people they know are directly at risk and impacted by the flooding. The ability of the fire department to create a sustainable long term solution to this problem is very limited. They do not have the expertise nor can they attract the required funding to develop and implement large scale long term infrastructure improvements.

Karlovac FD

Figure 6. Personel from Karlovac Fire Department and visiting Virginia Tech Graduate students (Source: Virginia Tech IFE June 2018)

Local government entities are interested in finding solutions as more frequent and larger flooding events cost the city money, as well as divert resources (human and capital) that could be used for other projects. They are also interested in limiting the potentially negative political impacts that could result from their constituents frustration with the response to flooding. Karlovac wants to improve its and the economy of the area, and its attractiveness as a place to live. This will improve their tax base. The local government aims to learn new technologies for flood mitigation. National level agencies are motivated to mitigate flooding in order to alleviate political pressure from the citizens of Karlovac.

Businesses within Karlovac seek to reduce negative economic impacts as a result of flooding. Including damage to and loss of assets, and reduction in workforce capacity. Improving Karlovac’s capital investment potential from both internal and external resources to increase business growth.


Screenshot (23).png

Figure 7. Box Barriers being filled with sand and gravel near Karlovac by personnel from Croatia Waters (Source: Lozancic 2018)

There are multiple strategies being implemented by both Croatian Waters and local authorities and entities. However, there are different motivations, priorities and abilities between these stakeholders which can put them in conflict. Until now much of the work conducted has been either emergency response together with limited, and predominantly temporary infrastructure installations such as box barriers. Flooding events appear to have been highlighted by national media which has helped raise awareness of the problem across the country. The primary tactical objectives of box barrier installation is coupled with a river Sava diversion channel.

Croatian Waters has produced various materials outlining the overall strategy for addressing flood damage mitigation in the city of Karlovac. The total cost of the 4 phases (Figure 8) including the canal is estimated at €46.7 million or 352.5kn million (Figure 9). Various engineering controls of flood mitigation include a canal, diversion gates, weirs, earthen embankments, a flood retention reservoir, and retention wall (Flood Protection System of City of Karlovac, n.d.).

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Figure 8. Project Phases (Source Flood Protection System of City of Karlovac, n.d.)

Project Cost Estimate.jpg

Figure 9. Cost Estimates (Source Flood Protection System of City of Karlovac, n.d.)

Flood mitigation activities appear, at times, to be uncoordinated and funded differently by local, national and international stakeholders. An example provided by a local stakeholder was of a flood barrier that was installed in the incorrect location and subsequently failed. National agency/government efforts including emergency response by the military are funded by the national government. Longer term infrastructure installation which carry a higher price typically requires a variety of funding sources based upon a core of EU funds. Sources of local funding are not 100% clear but include local government support and private industry donations in the form of equipment and expertise.


All water related issues, including preventing and responding to flooding events in Karlovac, are the direct responsibility of Croatian Waters. However, the reality is that the most effective responses to date appears to have been implemented or initiated by the local fire department. Differences in priorities, funding cycles, capabilities and approaches to the problem by these two different levels of jurisdiction have apparently resulted in conflict and an uncoordinated response to flooding events. The uncoordinated responses have been echoed by various stakeholders we met with, such as the Karlovac Fire Department, and River Sava non-profit, which noted that national environmental engineers and technical decisions may have not been in line with local solutions to flooding.

The stark distinction between economic stimulus and water resources is geographically divided. Due to the mountain chains the catchment area of the eastern coast is very limited so that only a small volume of freshwater from Croatia (20% of Croatia’s rivers by the volume of water) drains into the Adriatic Sea (Geres, 2009). The tourism industry, whose success depends on the Adriatic Sea coastline and the offshore islands, contributes significantly to the economy and generates about 85% of Croatia’s foreign exchange (Geres, 2009). Considering water resource stressors from tourism on a geographic region of Croatia which only receives 20% of the nations freshwater volume, and generates about 85% of the nations foreign exchange; we can reasonably believe that national efforts towards water management improvement are focused on the regions which generate foreign exchange revenue, as opposed to the other regions which do not.

Flooding in Karlovac could be considered a simple environmental process, yet also a very complex one when introducing the human element, incorporating interactions of socioeconomic, political, and physical considerations. Figure 8 explores the interactions between some of elements and actors of the systems.


Figure 10. The system diagram showing flood related system dimensions and their interactions.

The recurring flooding events in Karlovac could be attributed to various environmental changes in sync with a lack of investment and regular preventive measures, including urban planning schemes to protect the townspeople of Karlovac. This idea is supported by the conclusions expressed in Geres, 2009; “Analyses have also shown that due to partly non-repaired war damage, as well as due to a longer period of insufficient investment in the development and regular maintenance of protective systems, the safety of the population and assets in many potentially flood-exposed areas has been significantly reduced.”

There is clearly a reliance on European Union funds for most infrastructure projects.  The benefit of this is that it provides access to expertise and products that may otherwise not be easily accessible.  Give the brain drain as described in the Demographics section this is important. The downside of engagement with the EU is the high level of bureaucracy and the centralized nature of project prioritization, planning and implementation.

Prior to the accession of Croatia to the EU, Croatia has been participating in various EU programs such as the  Instrument for Pre-Accession Assistance (IPA), (Instrument for Pre-Accession Assistance, n.d.). The EU “twinning” program which is an instrument for institutional cooperation between EU member states and partner countries, provides IPA nations various benefits (Twinning, n.d.), Croatia being one of them.

EU IPA 2010 Programme for Croatia TWINNING PROJECT (Source: Promo Video Produkcija)

Click hyperlink to play or copy and paste url:

During the 2010 twinning programme in which Croatia is identified in the IPA I phase, a conglomeration of EU nations such as the Netherlands, Austria, and France worked collectively, in partnership with Croatian government agencies and local stakeholders to establish a number of outcomes addressing flooding.

The international EU programme was for the benefit of Croatian Waters and the ministry of agriculture and implemented by:

  • The Dutch Government Service for Land and Water management of the Ministry of Affairs
  • Austrian Environment Agency
  • The French International Office for Water (French  non-profit association under French law declared to be in the public interest by the Decree of 13 September 1991. IOWater was born from the merger of three organizations.)

Karlovac was one of the two locations selected in Croatia to develop flood mitigation plans. The mandatory results achieved included:

  • mathematical hydraulic models prepared and tested
  • flood hazard maps and flood risk maps prepared
  • 6 guidance documents on flood topics prepared
  • Strengthening relevant institutions

The 15th month project with 535 working days established 21 missions, 28+3 project activities utilizing 37 experts from the netherlands, austria, and france. The Croatian beneficiary institutions addressed flood related conditions by participating in working sessions, field visits, workshops, conferences on topics as decision making processes, data collection, modelling, mapping, structural and non-structural measures and further stakeholder participation. (Promo Video Produkcija, 2014)


Croatia has progressively been implementing flood control strategies and tactics since becoming a member of the EU in 2013 through various EU legislation, funding and cooperative programs. The Karlovac flood protection program is part of the greater Karlovac-Sisak  Flood Protection Project, which aims to prepare Karlovac to reduce flood risks by 85% (Babić 2016).

Funds for improvement, reconstruction and further development of protection systems are non-existent (Geres, 2009). This example is exhibited by the statements and actions of the Fire Department official, engaging in research, and aggressive preventative measures such as construction of flood control gates coupled with research and implementation of flood control technologies proven in other countries, yet deemed illegal and unofficially sanctioned by the National government.

Current water management has only about 65% necessary funds available for regular technical and economic management of watercourses, water estate and water structures (Geres, 2009).

While the urban and environmental engineering tactical goals intend to reduce flood risk, the progress of the project serves to reinforce the idea that Karlovac and it’s citizens will be protected from future flooding. Establishing the idea of flood control of intense and regular flooding events may serve to provide stakeholders with a sense of security and accomplishment. Ultimately, it cannot be absolutely determined if the the overall process of recent flood mitigation in Karlovac may be enough to counteract the effects of global warming and other undetermined hydrogeologic elements.


The extent that climate change will impact Karlovac is still relatively unknown. There are speculations and hypothesis on what the effects will be, but no definitive studies or conclusions have been made at present. Researchers have analyzed reports and databases to determine what areas, such as Karlovac, will experience as the climate starts and continues to change,  but again, these studies are only speculations. Some known changes that will occur is that across croatia, temperatures will rise to a few degrees and change in the amount of precipitation an area receives will vary throughout the country (The World Bank 2015). The area around and including Karlovac is expected to receive 32% more precipitation during fall season by 2071 (The World Bank 2015).

Another unknown is whether funding for flood mitigation projects for Karlovac will be available due to competing government priorities such, as projects dealing with the capital city of Zagreb. Stakeholder interests will ultimately influence funding for future flood prevention projects and infrastructure upgrades in Karlovac.

Karlovac is redesigning its image as a tourist location. The impacts of climate change to Karlovac’s new image is uncertain. It is also uncertain how long tourism will impact Karlovac’s economy, nor is it known how well tourism will take off in Karlovac. When devastating flood events do occur, it impacts local businesses and residents alike, especially if they don’t have flood insurance; “Financial insurance of property from uncovered flood risks is virtually non-existent” (Geres, 2009). Statements during our interviews with the Fire Department Officials, and representatives at the Croatian Ministry of Energy and Environment confirmed Geres’s statement.

With the uncertainty climate change will have on Karlovac and its surrounding areas, it is imperative that stakeholders work together to protect the history, economic stability and residents of Karlovac.


Stakeholders at all levels, but particularly at the local level, acknowledge the dire need for future flood mitigation. Croatia has also identified Karlovac as a high risk location for floods via the European Union’s mandate requiring all members of the union to identify high risk areas. Multiple stakeholders have their own ideas and approaches on how to implement future flood mitigation for Karlovac. The City of Karlovac Fire Department has been proactive, by researching and testing new flood prevention technologies. Croatia Waters have the same objectives as the local stakeholders; prevent destructive floods. However, they have been collaborating very little with local agencies and seem to implement projects on their own, with limited local government input.

Croatia’s government needs to assist Karlovac with obtaining more appropriate funding for proactive flood mitigation projects instead of waiting for another destructive flood event. The

The floodplain management project in Karlovac is a small part of the bigger picture of flood mitigation and water resource management for downstream users as it is directly tied into the hydro-geologic cycles of the upper and middle Sava river floodplain, which can be seen to the west or right in  Figure 9. Efficient management of of Croatia’s abundant water resources flowing through the City and County of Karlovac have deep implications for Karlovac’s citizens, downstream users and ecosystem services.

Cooperative action taken between Croatia and the EU has led to significant progress in remedying Karlovac’s threat of intense and frequent flooding. International partnerships, and action taken by the fire department to improve the cities flood resilience is a testament to the citizens dedication to accept environmental challenges that have been characteristic of the region.

Watershed Impacts.jpg

Figure 11. Source: Babic, 2016


We would like to thank the City of Karlovac’s Fire Department and their Chief, for the informative presentation, tour of the History of Karlovac Fire Department Museum, and for hosting a delightful dinner. We would also like to thank the brave men and women of the Karlovac Fire Department who help protect and rescue residents who are impacted by these recurring floods; and for their dedication to their city by researching the best available technology and strategies for mitigating and preventing devastation from future flood events.


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