Journal of Environmental Science and Engineering B 1 (2012) 34-40 Formerly part of Journal of Environmental Science and Engineering, ISSN 1934-8932 D DAVID PUBLISHING

Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use

Zsófia Derts and László Koncsos Department of Sanitary and Environmental Engineering, University of Technology and Economics (BME), Budapest H-1111,

Received: July 13, 2011 / Accepted: August 8, 2011 / Published: January 20, 2012.

Abstract: The actual situation of the Tisza Valley traditionally used for land farming is basically determined by the consequences of the river regulation of the nineteenth century which aimed at the extension of the intensive agriculture, by the extreme water regime of alternating periods of flood showing a deteriorating trend and drought related to the climatic change; and by several environmental problems induced mainly by the land use. The objective of the article is to prove the regional advantages of a proposed technical solution to mitigate the flood risk with a special regard to the land cover. Hydrodynamic modeling results prove that the best technical solution is given by a combination of different strategies containing the inundation of deep floodplains-areas regularly covered by water before the river regulation works and, globally, by an important mitigation of flood damages, the costs of solution would be surely covered in the longterm. By means of its natural-resembling operation, the regular water cover would allow a multiple use of water, contributing to the solution of the simultaneously existing aridity problem, and, the development of the floodplain landscape management would help improve the ecological and the economical upgrading of the region.

Key words: Aridity, deep floodplain, flood control, land use, landscape management.

1. Introduction geographical centre of Europe [2]. The Tisza River can be divided into three sections (upper, middle and The Tisza Valley in Hungary has suffered of grave downstream section) [1] from which in Hungary flood damages and, looking back to the extreme flood mostly the middle and downstream sections can be events of the past decade, the risk shows a found, both characterized by a meandering platform deteriorating trend. What is more, the situation of [2]. According to its hydrological situation, the these areas, characterized by flood damages is precipitation in the Hungarian Tisza Valley is less aggravated by aridity and environmental quality problems related to the land use. than 500 mm per year. The mean annual discharge at 3 The main objective of this article is to propose an the mouth of the Tisza River is 792 m /s [2]. The effective technical solution for flood mitigation, to Tisza Valley has an extreme water regime: smaller analyze the limits of its execution with the current flood events occur in every 1-2 years and larger ones land use and to give a suggestion for the complex in every 5-6 years [3] regularly alternating with issues of the Tisza Valley. drought within short periods.

1.1 Geographical Situation of the Tisza Valley 1.2 Human Impacts

The 157,000 km2 large Tisza River basin takes part In Table 1, the actual problems of the Tisza Valley of the River basin [1] and can be found in the mostly related to human activities are summarized. 1.3 Possible Technical Solutions Corresponding author: Zsófia Derts, Ph.D. student, main research field: environmental modeling. E-mail: [email protected]. The following interventions are possible to solve

Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use 35

Table 1 Problems of the Tisza Valley related with causes and issues. Causes Problems Issues Increased frequency, occurring period Flood protection, water supply for Climate change [4] and level of flood events; aridity of ecological and agricultural (human) inner areas needs Material damages from flood levels Deficiencies of the actual flood Development of the flood protection exceeding the dykes and from protection system [5] system geotechnical catastrophes Degrading the water exchange between Sedimentation of the floodplains [6] the main river bed and the floodplain; Increasing flood risk Improving water exchange between the Necessity of raising dyke levels [1]; Tisza and its flood area; improving the Regulation works: meanders cut, river sinking of the main river bed leading to hydraulic conductivity of the floodplain length shortened, slope increased, the decline of the groundwater level; by regular maintenance velocity increased, cross-section 167 larger and numerous smaller reduced [1] oxbow lakes disconnected [2] 96% of the original 25,900 km2 ancient floodplains isolated [10]; decrease of Changing the land cover by taking in groundwater level [2]; Extension of drained areas for intensive account the nature and the original local leading to the disadvantageous agriculture [7-9] circumstances; and by satisfying human modification of the water balance and needs for nourishment to the extension of arid areas; decrease of biodiversity; Application of inappropriate technologies and of excessive amounts Diffuse nutrient loads runoff and soil Adequate technologies, development of of chemicals in agriculture; deficiencies erosion increased [2], decrease of the sewage and waste water treatment of the sewage and waste water groundwater quality [11] system treatment system [11] Establishments (residential and other Material damages caused by major Revision of the permission system for buildings) in areas anciently covered by flood events constructions water Revision of the agricultural financial Further extension of intensive support system, and research for one Agricultural financial support system agriculture land use that supports land uses more adaptive to the nature the flood risk problems: water storage in deep floodplains (anciently regularly  The correction of the flood levees among the covered by water) during flood waves would be a Tisza by repairing the problems of designing and of technically efficient way to mitigate flood risk. Our technical condition; objective is to analyze the feasibility of this idea in the  Amelioration of the hydraulic conductivity of the aspect of the land cover. floodplain; 2.1 Available Information  Emergency flood reservoirs filled up in every 30-40 years as an average in case of extreme flood For our research work the following georeferenced waves [12]; digitalized maps, GIS data and descriptive literary  Regular Inundation of low elevation areas called information were available: deep floodplains which used to be covered by water  The former (nineteenth century) [7, 8] and for 2-4 months per year before the nineteenth century present (CLC 50) land cover of Hungary [9], Google regulation works [13, 14], to increase the efficiency maps, 50*50 m cells morphologic model for the Tisza of the shrinkage of floods. Valley;  GIS data for drought and flood risk (provided by 2. Methodology VITUKI Environmental Protection and Water According to our previous research work [15], Management Research Institute of Hungary);

36 Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use

 The Hungarian map of the areas anciently comparative analysis of the ancient and current land regularly covered by water (flooded areas and covers and the potential risks for each chosen deep wetlands); floodplain.  Historical landscape and ethnographical 3. Model Analysis and Calculation Results descriptions of the Tisza Valley [16], descriptions and modeling results concerning the flood risk and its As a result of the 2D hydrodynamic simulations, a influencing factors in the Tisza Valley [3-6, 14] etc.. sum of 2.5 milliard m3 of regularly inundatable deep floodplain capacity has been found for the Hungarian 2.2 Hydrodynamic Modeling and Inundation Tisza section without affecting seriously the Frequency Calculations surrounding settlements (see Fig. 3). In a previous phase of our research [15], the The water level decreasing efficiency of the deep potential technical solutions and their combinations floodplain reservoirs was compared in case of several were compared by computer models connected with settings for historical flood records of the last fifteen each other: years, and it has revealed that however each flood  2D hydrodynamic model based on the equations wave is different; the average flood level mitigating of shallow waves [17] resulting connected water level, effect would have always exceeded 1.0 m on the reservoir volume and water surface data; Hungarian section of the Tisza River. The  1D hydrodynamic model based on the optimization of the studied system has resulted that Saint-Venant equations [12] calculating the flood 20-30 meters large sluices and continuous and level decreasing effect of the deep floodplain bidirectional operation would be ideal in a way that reservoirs in case of different operational settings; the sluices would be closed when the water level  A flood risk model determining the normal exceeds the maximum allowable level at the entering distribution intervals of different types of material point (to prevent flood damages in the settlements and damages in actual and designed conditions in establishments). different scenarios by Monte Carlo simulations [11]. From the flood damage cost statistics given by The results of the mentioned modeling analysis Monte Carlo simulations of 5,000 generated flood processes constituted (among others) the input data for waves it can be concluded that with the supplement of the empirical relationship analysis of the associated the dykes 0.5 m above the design flood level, by water volumes and yearly occurring frequencies for maintaining the hydraulic conductivity of the each potential deep floodplain reservoir. floodplain and by defense activities during flood The result of these calculations will be applied events (an important element of the Hungarian flood during the optimization of the water level of the protection system), the material damages could be entering point and water volume of the deep decreased even to their 0.5-1.0% compared to the floodplain reservoirs. estimated damages taking into account the sedimentation of the floodplain and the climatic 2.3 GIS Analysis change. (In case of a decision concerning the After the hydrodynamic model analysis, the contour improvement of the flood protection system of the of the inundatable areas are visualizable and can be Tisza Valley, besides the estimated benefits–the cut by software tools in georeferenced maps of the decrease of the material damages, the costs of former and present land cover, the Google maps or the investment and maintenance have to be taken into map of flood and drought risk. This allows the account.)

Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use 37

In Fig. 1, the yearly occurring frequency result that the areas chosen for being inundated were (determined from hydrological data from the past 25 anciently regularly covered by water and, as a result of years) of the water cover can be viewed associated to the nineteenth century regulation works they have the possible water volumes of the given deep been disconnected from the Tisza and its flood waves. floodplain area. These results are calculated for all of The current land use-except for one chosen deep the chosen deep floodplains and will constitute the floodplain which is a Ramsar wetland area-is input data for the further optimization processes. dominated by arable lands of large and small fields, giving a mean proportion for intensive agriculture of 4. Landscape and Climatic Risk Analysis 73% to the total of the areas. This result is proved by Results the visual analysis of the latest Google map pictures. 4.1 Land Cover Analysis Results The aggregated results of the land cover analysis can The analysis of the former land cover has given the be studied in Fig. 2.

Fig. 1 Reservoir water volume in function of the yearly occurring frequency of the water cover.

Fig. 2 Land cover proportions in the selected deep floodplains of the Tisza Valley.

38 Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use

Ukraine

Slovakia Tisza River

Danube Austria River Potential deep Hungary floodplain reservoirs

Rivers Frontier Flood Croatia Drought

Fig. 3 Risk of flood and of drought in the Tisza Valley.

4.2 Risk of Flood and Drought Several climatic environmental risks concern the Tisza Valley such as higher and more intense flood A significant part of the Tisza Valley is concerned waves in modified frequencies and occurring periods, by the environmental risks related to the extreme and, in the same time, drought in the inner areas now water balance of the region. Among the chosen areas, disconnected from the ancient water exchange 92% of their sum is characterized by flood risk which processes. In the same time, the actual land use of the is not surprising in view of the ancient, wetland Valley shows a significant majority (73%) of intensive dominated land cover. The drought, a more and more agriculture which is not only contradictory but also serious environmental risk factor of the climatic change, affects approximately the southern 2/3 part of disadvantageous due to the diffuse nutrient inputs in the Hungarian Tisza Valley, or 69% of the sum of the the soil and in the groundwater and because of the chosen deep floodplain areas (See Fig. 3). excessive water use for irrigation. However this type of land use of the concerned population is 5. Conclusion and Suggestions unsustainable and contradicts with the own long term Concerning the mitigation of the increasing flood interest of the inhabitants (water supply of sufficient risk the inundation of deep floodplains during flood quantity and quality, healthy soil), because of the waves through 20-30 meters wide sluices would be actual agricultural financial support system, the effective, but should be completed by the supplement intensive agriculture will be very hard to be turned of the dykes 0.5 m above the design flood level; and into a sustainable land farming adaptive to the local the flood level could be more efficiently mitigated by circumstances. the maintenance of the hydraulic conductivity of the By reconnecting the more and more arid areas to floodplain and by defense activities during flood the water exchange processes (similarly to the land events (see detailed results in Ref. [14]). farming of the ancient Tisza Valley), the inundation of

Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use 39 deep floodplains would insure a regular water supported by the New Hungary Development Plan covering and would lead to a sustainable solution for (Project ID: TÁMOP-4.2.1/B-09/1/KMR-2010-0002). the problems of ecological and human water supply. The results discussed above are supported as well by To contribute to a landscape management adaptive to the grant TÁMOP-4.2.2.B-10/1--2010-0009. the regular water covering and to moderate the References conflict caused by the support of an unsustainable [1] I. Vágás, The floods of the Tisza River, Documentation land use, the agricultural allocation system should be and Retraining Centre of Water Management, Budapest, obviously reviewed and modified. This way, the Hungary, 1982. (In Hungarian) spreading of nature-friendly agro-technologies could [2] K. Tockner, U. Uehlinger, C.T. Robinson, Tisza River, in: also be supported. Rivers of Europe, Elsevier Ltd., 2009, pp. 59-112. [3] L. Somlyódy, Strategic basics of the Hungarian water For the sake of the complex objectives of the Tisza resources management, in: Strategic Issues of the Valley, other measures are also required to be Hungarian Water Resources Management, Hungarian executed. To mitigate the material flood damages, the Academy of Sciences, Budapest, Hungary, 2002, pp. location of the buildings plays also an important role. 23-45. (in Hungarian) [4] B. Nováky, Climatic change, water and sustainable water Hence, the revision of the permission system for management, Report, Department of Sanitary and constructions is also recommendable to prevent Environmental Engineering, Budapest University of avoidable material damages in the areas potentially Technology and Economics, Budapest, Hungary, 2008. (in Hungarian) affected by flood. On the other hand, social tasks [5] Halcrow Water, Hungarian flood control development should be performed to draw the attention of the and recondition project: Feasibility study, Report, concerned population to the importance of the Budapest, 1999. (in Hungarian) sustainable water balance and to the technical [6] L. Koncsos, Zs. Kozma, Modeling of floodplain sedimentation on the Hungarian Tisza, in: Harmonizing possibilities of land farming. the Demands of Art and Nature in Hydraulics, Concerning the research process, by means of these 32nd Congress of IAHR, Venice, Italy, Theme A2.b, latest results, the next phase to achieve will be the 2007. [7] Arcanum Data Base Ltd., The second military survey: optimization of the reservoir entering point levels The entire area of the and Temes taking into account the hydrological probability on high resolution coloured map segments, 1806-1869, calculations; the analysis of the vegetation changing [DVD], Budapest, 2006. as an effect of the water balance; and, to find [8] Arcanum Data Base Ltd., The third military survey: The entire area of the Austro-Hungarian Monarchy on high ecologically sustainable agricultural vegetation types resolution coloured map segments, 1806-1869, [DVD], to insure the subsistence of the inhabitants for the long Budapest, 2007. term, in case of different scenarios of the climate [9] European Environment Agency (EEA), CORINE Land Cover data base, 2006. GIS layer, available online at: change. http://www.eea.europa.eu/data-and-maps/figures/corine-l and-cover-2006-by-country. Acknowledgments [10] UNEP, Rapid Environmental Assessment of the Tisza River Basin [Online], UNEP/ROE and This work has been undertaken as a part of the UNEP/DEWA/GRID~Europe, in collaboration with WateRisk and SCENES projects at the Department of UNEP/-ISCC, Prepared by K. Burnod-Requia, Sanitary and Environmental Engineering, Budapest 2004, University of Technology and Economics (BME), and http://www.grid.unep.ch/product/publication/download/ti sza.pdf. also supported by the “Development of [11] VÁTI Hungarian Public Nonprofit Limited Liability quality-oriented and harmonized R+D+I strategy and Company for Regional Development and Town Planning, functional model at BME” project. This project is Conceptual study on the regional development of the

40 Flood Risk Mitigation in the Tisza Valley by Deep Floodplain Reservoirs: The Effect on the Land Use

Tisza Valley, Budapest, 2004. (in Hungarian) [15] L. Koncsos, Zs. Derts, Flood risk reduction and water [12] Budapest University of Technology and Economics, quality management by deep floodplain inundations, in: Department of Sanitary and Environmental Engineering, Proceedings IWA Specialist Conferences/12th IWA Scientific background of the issues concerning the International Conference on Wetland Systems for Water mitigation of floods and the amelioration of the Pollution Control/12th IWA International Conference on conduction of high water levels-the Development of the Wetland Systems for Water Pollution Control, Venice, Vásárhelyi Plan (First part), Budapest, 2003. (in Italy, Oct. 4-8, 2010, pp. 1340-1346. Hungarian) [16] G. Molnár, The floodplain land farming, in: At the Tisza [13] BOKARTISZ, The treatment of the floodplain woods， River-Thoughts of Nature and History, 1st ed., Public Company of Ecological Economics and Landscape Ekvilibrum Press, Zalkod, Hungary, 2003, pp. 86-97. Rehabilitation of Bodrogköz, Karcsa, Hungary, 2005. (in [17] L. Koncsos, ARES software package for decision support Hungarian) on rainfall-runoff and flood modeling, in: Flood [14] L. Koncsos, Flood Regulation of the Tisza in the Management Challenges in the XXI Century, Carpathian Basin, Hungarian Association of Nature Dutch-Hungarian Workshop, , Hungary, 2003, pp. Conservation, 2006. (in Hungarian) 68-77.