Europe’s natural flood prevention
Europe’s prime source of natural flood prevention under pressure from dams and inland navigation
Slovenia, Croatia, Bosnia-Herzegovina, Serbia
From its source in the Slovenian mountains to its mouth into the Danube in Belgrade, the Sava River represents one of Europe´s ecologically and culturally most interesting lifelines. Along its total length of 944 km and total catchment area of 97,713 km2, the Sava River connects four countries and more than 8 million people who live in and from its catchment area. Large sections of the Sava River are still free flowing and extensive floodplains and alluvial forests have been preserved until the present day. The annual cycles of temporal flooding in winter and spring have shaped the face of this region and created rich cultural landscapes and strong traditions of the people living in harmony with their river.
The large natural floodplain areas in the middle section can store over 2 billion m3 of water, saving lives and properties in downstream towns such as Sisak, Slavonski Brod or Belgrade. These floodplains provide probably the most exceptional natural flood prevention system in Europe.
The outstanding ecological value of the Sava River - its oxbows, meanders and floodplain forests - has already been acknowledged. Five areas totaling 74,888 ha have been designated as Ramsar sites: Lonjsko polje and Crna Mlaka (HR), Bardača (BiH), as well as Obedska bara and Zasavica (RS). While most parts of the Sava River in Slovenia and Croatia have already been included in the EU Natura 2000 network, the river remains largely unprotected in Bosnia and Herzegovina and Serbia due to the lack of a coherent system of protected areas supported by national agencies.
A total of 49 highly important sites with respect to biodiversity were identified along the Sava, covering an area of 368,921.74 ha. However, there are huge scientific gaps regarding the ecological role and biodiversity of the Sava. On long stretches the river flows untamed and free and without any artificial limitations and thus provides typical riparian bird habitats, for instance for the Sand Martin (Riparia riparia) which breeds in steep walls, or the Common Tern (Sterna hirundo) nesting on gravel and sand islands.
The floodplains play a key role in regards to the biological diversity of the region. Temporal flooding makes the Sava´s floodplains a perfect feeding ground for several heron species or White storks (Ciconia ciconia) - which breed on nearly every roof in the riparian villages along the main river course. Rare European Spoonbills (Platalea leucorodia), which have been in dramatic decline in South Eastern Europe in recent years, still find feasible breeding grounds and good feeding conditions on the flooded pastures to raise their chicks.
The Huchen in Slovenia
The still free-flowing Slovenian stretch of the Sava hosts a rarity, which was once widespread across the entire Danube basin: the Huchen, also referred to as Danube Salmon. The Huchen (Hucho hucho) is the largest of all salmonid species. In order to reproduce, the fish requires fast-flowing and grave-rich rivers. Such rivers have become rare, however, the Sava and its tributaries still provide these habitats. But for how much longer? Even these last refugiums are now threatened by numerous projected hydropower plants. If these plans are implemented as forseen, the Huchen won’t stand a chance. Find our study and other downloads to this end: The Huchen Hucho hucho in the Balkan region
What’s more, Sava’s catchment area hosts the largest network of alluvial forests in the Danube basin, primarily composed of English oak (Quercus robur) and ash (Fraxinus angustifolia). These forests provide habitat to important European breeding populations of the Lesser-spotted Eagle (Aquila pomarina) and the White-tailed Eagle (Haliaeetus albicilla), as well as for a population of the rare and shy Black Stork (Ciconia nigra).
Social and cultural values
Social and cultural values
Over centuries, people have adapted to the flooding: the Sava´s floodplains are characterized by rare livestock breeds, such as the Black Slavonian, the Krsko or the Turopolje pigs feeding in the floodplains and swamps along the river course. Even today, the traditional practice of breeding Posavina horses and cows in the open floodplain during most of the year is still in place. Old traditions and rituals are still being nurtured along the Sava and the villages along its course are characterized by typical wooden houses, with the ground-floors more or less unused to adapt to the natural pulse of the river. The Sava is the main symbol of regional identification for the people living along its banks. They have generated a rich variety of regional products, such as honey, cow cheese and regional pork products. Besides extensive agriculture, forestry is a main source of income and plays a key role in subsistence. Nature tourism has developed well in several locations along the river, as for example along Sava’s upper reach in Slovenia, in the floodplains around Lonjsko Polje Nature Park in Croatia, and along major tributaries such as the Una River in Bosnia-Herzegovina. This might potentially turn into a main economic sector.
The Sava River is under attack from two sides: the integrity of the upper and middle section is threatened by new hydro dam projects while the lower part is at risk of regulations due to plans for a navigational upgrade.
There are 29 existing hydropower dams in the upper part of the river basin. These dams cause significant downstream problems through disruption of sediment flow resulting in river bed incision as well as surface and groundwater level decrease. Due to the lack of sediment, the river bed has already eroded up to 6 m in Zagreb and drinking water supply for over one million residents is at stake.
Despite these facts, nineteen additional hydropower dams are projected along the Sava alone and almost all tributaries are subject to further development plans. According to a recently developed project named “Zagreb on Sava”, seven additional hydropower plants are to be built on the Sava between the Slovenian border and Sisak, along with a 34 km long bypass canal to divert flood waters around the Croatian capital.
The lower section of the Sava River is threatened by unrealistic inland waterway development projects which involve broad regulations of the still natural flow of the river in this section. An upgrade of the Sava navigation from class III to IV between Sisak and Slavonski Brod (2.5 m navigation depth) and from class IV to V between Slavonski Brod and Belgrade (2.5 m to 2.8m depth) is projected even though the river is barely used for commercial shipping (annual capacity: 400,000 tons) and alternative transport via the new highway and the railroad is available.
These navigation plans would lead to the complete deterioration of the Sava River: 106 new river training structures and 27 new embankments would have to be built in Croatia only, while 1.7 million m3 of sediment would have to be excavated in order to fix and deepen the navigation corridor. These constructions would destroy the meandering processes; river and floodplains would be further disconnected and old oak wood forests and oxbows along with its rare species, such as the Spoonbill colony in Krapje Đol (HR), would be sacrificed. Economic needs and benefits, as well as environmental and other costs of such projects have never been properly assessed. Nevertheless, these navigation projects are fully endorsed by the International Sava River Basin Commission and relevant water management lobbies.
- The unique flood protection system of the Sava River is threatened by dam and navigation projects
- Significant river bed erosion is already threatening the livelihoods of millions of inhabitants
- Further river degradation would increase the risk of floods in downstream communities, towns, and settlements
- Further impairments of the river’s flowability and the loss of spawning grounds due to constructions and regulations will put the population of the Huchen, which is protected by EU Habitat Directive, at risk
- Exceptional biological and cultural values of the Sava region are the backbone of sustainable development in the region
- No more hydro-power dams on the Sava River to be built, particularly in the lowland areas and NATURA 2000 sites.
- Renaturation measures for the Sava in Slovenia in order to stabilize and enhance the population of the Huchen in line with the EU Habitat Directive.
- The government of Slovenia to assure the urgent implementation of measures to mitigate downstream impacts of existing reservoirs, particularly concerning the sediment deficit and consequent river bed incision.
- No upgrading of the existing navigation class – adapting the vessel to the river, rather than the other way around.
- The EU not to finance projects that clearly violate respective EU directives.
- The importance of the Sava River for navigation to be reassessed by an independent expert group (including NGOs) and alternative transport systems such as railways, pipelines and roads to be taken into account. A sound cost/benefit analysis to identify the environmentally and economically best solution for the transport of goods along the Sava corridor.
- A large river restoration program for the entire still free-flowing main river section from Slovenia (Krsko) to Serbia (Belgrade) to be developed and implement