Floodplains include unique environments shaped over a long time horizon along rivers and smaller streams and formed by alluvial sediments. As floodplains are flat, often with highly fertile and well-accessible land, they have become the intrinsic focus of human society-while providing a variety of goods and ecosystem services. Intensive land use of floodplains is degrading their natural values and significantly reducing their ecosystem functions and services. A significant part of these key services is related with the ability of floodplains to retain water and nutrients, which can be understood as a flood control and a water-retention function. Although these ecosystems serve a number of other basic functions, the importance of floodplains as a place for water retention during extreme discharges caused by intense rainfall or snowmelt and the supply of water in times of drought are essential under conditions of global change. In order to increase the ability of floodplains to perform these functions, it is increasingly required to preserve the connectivity of rivers with surrounding floodplains and adapt human activities to maintain and restore river ecosystems. This article reviews the recent understanding of floodplain delineation, the most common causes of disturbance, the ecosystem functions being performed, discussing in turn the measures being considered to mitigate the frequency and magnitude of hydrologic extremes resulting from ongoing environmental changes.

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Urban development causes multiple water losses. Some of them may be ignored but some could have a huge influence on the whole catchment, including soil drought. As urban sprawl rises, space for unaffected infiltration and retention is increasingly limited. The objective of this study was to backcast and to estimate water-retention loss due to urbanization during the period of 1990–2018. We used landcover data, meteorological and hydrological data and data on soil water-holding capacity. Water-retention loss was expressed as soil water retention capacity loss, net precipitation loss and total sum of precipitation loss. Historical change in urban extension has led to large impacts on the hydrological cycle of the study area. Progressive urban development caused water-retention losses which range from 3.380 to 14.182 millions of cubic meters—depending on the methodology used. Hydrological analysis showed the lack of a significant trend (decrease trend) of low flow which is caused by the high percentage of natural land use in the upper part of catchment. Our results show that backcasting of water retention change using CLC data (a) brings new and plausible data on retention loss, (b) is possible to replicate and (c) data used are common and easy-to-get.

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The risks of accelerated runoff and its larger amounts brought by urbanisation include increased flood flows and pollution of downstream ecosystems. One of the most significant permanent effect of urban sprawl is soil sealing, which alters natural infiltration and runoff. In addition to imperviousness, the increased runoff from sealed and compacted surfaces results in increased sedimentation of stream ecosystems with contaminants. In most urban planning strategies, water related ecosystems have already become the fundamental components of the integrated urban landscape management, but still have been referred to as objects of protection or rehabilitation; not as management tools. This paper shows how soil sealing significantly affects urban environment and urban ecosystems health. It also demonstrates significant impacts of a city on downstream ecosystems. Data obtained from orthophotomap vectorization showed that the model urban catchment is relatively highly urbanized. 45% of model area is sealed mainly with buildings (40.41%), streets (31.01%), and parking lots (25.28%). Compared to natural basins, urban runoff is 64 times higher and carries a significant amount of pollutants.