How does a floodplain affect the landscape and ecosystem

Rivers have also been regulated to improve the supply of water to major cities; one of the largest such projects, the Poulaphouca Reservoir on the River Liffey, was commissioned in to serve hydro power generation and the water supply needs of Dublin city ESB The rivers Shannon and Lee have also been regulated for hydro power, with the Ardnacrusha hydro power plant the first to be commissioned, in ESB Severe water shortages were experienced in Dublin between and and it is planned to obtain water from the Shannon river system for the Irish capital Irish Water a , b.

Large-scale developments on rivers such as hydro power structures pose a considerable barrier to the movement of fish, and even the smaller constructions such as weirs have an impact on the movement of aquatic species King et al.

The management of water levels for hydro power schemes has also been shown to have a negative effect on breeding birds Mitchell , and on certain rare plant species, such as Inula salicina Martin Similarly there is evidence that increases in suspended solids, as a direct result of forestry and peat cutting activities, can in some river stretches affect key stages in the life cycles of aquatic species King et al.

The Dutch floodplains have fertile soils, which are rich in nutrients. From medieval times onwards tall fruit tree orchards were planted. In the s and s many of the orchards were uprooted for meadows. From onwards more orchards were reestablished, using more productive low fruit trees. In the lower parts of the floodplains meadows developed or, in the swampy areas, willows grew. Later, the opportunities for tillage improved due to better drainage systems and improved fertilization methods.

Horticulture occurred on coarse sandy soils with clay substrate Jongmans et al. The river area was also an important source for clay, sand and gravel De Mulder et al. The main biodiversity pressures in Dutch floodplains are related to alterations of hydrological conditions, agriculture, and soil pollution Table 2. The large-scale building of dykes started in the fourteenth century.

Initially, a low embankment was constructed along the border of the river to prevent the flooding of floodplain meadows. To prevent larger floods the much higher winter dykes were constructed, but they regularly broke due to stagnant ice Van Beusekom Human encroachment and construction of dykes in the period — resulted in a restriction of discharge capacity and a loss of retention area.

The Delta Plan, for which the first ideas were conceived in , was launched. After the flood, the focus was on the sea defense in the Dutch delta and large dams closed off all river arms from the sea. After a severe flood event in a programme was initiated to reinforce the inland river dykes. Also, at that time a debate started on the development of water retention areas as flood protection measures. Due to rising sea level and increasing discharge of the rivers, the second Delta Plan was launched in to prepare the Netherlands for the effects of climate change Kabat et al.

The biodiversity of the Dutch floodplains is impoverished, due to reduced natural dynamics and a history of intensive land use. The rivers were important for industry due to their transport potential and the presence of industrial water.

This resulted in severely polluted water for many decades and floodplains still have high contamination rates of heavy metals and PCBs.

The transport function of the river in combination with flood protection measures resulted in decreased natural dynamics where the river was managed to optimize transport and to minimize flood risks.

Land reallotment, accompanied by drainage of marshland and removal of old parcel boundaries added to the decline of biodiversity, in particular hedges and tree rows, typical for diverse cultural riparian landscapes Agricola et al. During the last centuries, floodplains in Germany have largely decreased, and on a national level, just one third of the former floodplains still exist BMU and BfN Local activities started long before the Middle Ages until , but were scattered and mainly confined around settlements.

They have been carried out mostly for the purpose of flood protection of settlements and agricultural areas. Systematic works began around the s with conceptually laid out river bed fixation, and cut-off of side channels, oxbows and meanders, often backed by dyke construction e.

It was the growing importance of steam boat navigation that triggered the second phase of corrections with the aim of establishing a stable and constantly sufficient water level in the fairway. Measures included groynes and weirs, bank revetments and training walls. Modern river correction was determined by new construction technologies and capabilities, optimizing the waterways for larger navigation capacities and on the Rhine following the Treaty of Versailles for the increasing importance of hydropower use.

The main pressure for biodiversity of German floodplains is without doubt the alteration of hydrological conditions, however, there are several additional pressures that are highly relevant Table 2.

Floodplain forests are largely managed for timber extraction with only a few near-natural stands remaining. In addition almost all natural floodplain habitat types are suffering from a loss of dynamics. During the last decades, traditionally used wet meadows and grazing areas have been largely removed or severely altered through intensive agricultural use. Recreational use of floodplains is still increasing in many parts of the country, being a threat to conservation goals as well as a chance for a better public appreciation of the value of floodplains and rivers.

The destruction of floodplain habitat is still ongoing. Chances arise from the current restructuring of the classification of navigable waterways for political and financial reasons, which might reveal opportunities for ecological development of certain river and floodplain areas. European WFD and FFH-Directives have triggered widespread activities of responsible authorities, but worries are that structural obstacles and political routine might reduce the needed measures to an inefficient extend.

However, a couple of restoration projects have been established recently and could serve as pilots for larger-scale planning. Demography and land use development in Slovakia was significantly associated with watercourses since the Paleolithic period. First settlements in the Mesolithic and Neolithic followed alluvia of rivers in lowlands and uplands Rulf Direct systematic human interventions into the channels of major Slovak rivers date back to the s, primarily in order to improve navigability and facilitate river transport.

The main biodiversity pressures in Slovak floodplains are related to alterations of hydrological conditions and alien species Table 2.

In Slovakia, almost one tenth of its territory km 2 has been drained, followed by the construction of water works, regulation of water flow and exploitation of peat, and subsequently leading to the disappearance of wetlands and water ecosystems. The lower Morava was shortened by more than 10 km by cutting off 23 meanders. The modern Danube is the result of the mid-flow channelization which happened from to The main aim of the project was the improvement of flood protection, river navigability and hydro power production.

This construction had an enormous impact on ecological conditions in the Danube floodplains. Many scientific works describe in-depth research and monitoring conducted to elucidate the effects on particular taxonomic groups of plants and animals Mucha The problem has increased in the last years, to the extent that a petition was sent to the Slovak Minister of the Environment in that contained detailed descriptions of the eradication of several fish populations.

Also the Tisza River catchment was prone to biodiversity loss due to historic mistakes in floodplain management such as the destruction of large wetland areas ICPDR In Hungary, landscape transformations influencing the present landscape started in the late eighteenth century.

Traditional floodplain management had been abandoned and the tillage area could be increased most efficiently by reducing the floodplain area and draining the large lowland marshes and moorlands found in the Tisza basin.

For more efficient transportation of crops, rivers had been shortened, and dykes had been built. Wide-scale river regulations started in Hungary in Somogyi Outside the newly built dykes, inland waters accumulated, which was mitigated by floodplain drainage with 40, km of channels Somogyi The majority of the floodways i.

Its abandonment resulted in a rapid degradation of the semi-natural habitats by the end of the twentieth century. The main actual pressures for Hungarian floodplain biodiversity are alterations of hydrologic conditions and invasive alien species, but also forestry, agriculture and effects of hydro power stations built outside the Hungarian border are highly relevant Table 2.

Despite all these pressures, three national parks have been established along the Danube, and nationally protected areas or Natura sites are relatively spacious Beckmann and Jen Multilateral dialogues started with the objective of transforming the current river management regime Sendzimir et al.

The loss of water had simultaneous ecological and social effects. The landscape change decimated not only the fish stocks but also the once famously rich avifauna: based on historical data, by the twentieth century nesting of white pelicans Pelecanus onocrotalus and common cranes Grus grus ceased, and the numbers of ducks, geese, herons, pygmy cormorants Phalacrocorax pygmaeus , great bustards Otis tarda and saker falcons Falco cherrug became markedly less Ecsedi Floodplain meadows, tall herb communities and marshes shrank to a fraction of their original extent.

Also in the Ukraine, large rivers, especially Dnieper, Severski Donets, Southern Bug, and their main tributaries are under constant anthropogenic influence. From to the main objective of the national economy was the river regulation for water engineering and land improvement. In the Dnieper storage reservoir cascade, for instance, consists of 1, large water storage reservoirs and 48, smaller artificial ponds Gusieva The river regulation history in Ukraine was initiated in , when the construction of Dniprovska hydropower station began, which was finished in From to , five more water reservoirs were created and the Dnieper flow became completely regulated Denisova et al.

On the Southern Bug, the distinctive feature is the intense regulation of flow by water basins and almost ponds with a total volume of 1.

The riverbed of the Ukrainian part of Seversky Donets is dammed three times. Many tributaries also have multiple dams; eight are located near Kharkiv, with more than ten around Sloviansk. In river basins of the middle-sized rivers of the Ukraine some small water reservoirs and many ponds were constructed since the s Vyshnevsky et al.

The most important pressures for Ukrainian floodplain biodiversity are alteration of hydrologic conditions and invasive alien species, but also settlements and industrial infrastructure, water pollution and eutrophication, hydropower, and mining and quarrying must be considered as highly relevant Table 2. The main environmental effect of river regulation was that huge areas of floodplains became permanently flooded, sometimes, also the second terraces of river valleys Avakjan and Sharapov ; Vendrov ; Vyshnevsky et al.

The landflood resulted in total destruction of natural vegetation and ecosystems of floodplains and in the occurrence of large areas of impoundments having quite a weak current. The areas closed to the reservoirs are depleted wetlands, which are frequently protected by dams Vyshnevsky et al. The flow regulation at the middle stretches leads to permanent flooding of bottomland and disturbance of their hydrological regime. Water levels are kept rather low in times of floods to protect the hydropower dams from destruction.

The absence of high water changed the regime that had existed for millennia, and thereby reduced the removal of excessive organic matter from inundated reservoirs and diminished the beneficial natural fertilization of the floodplain soil by floods.

In conjunction with the ploughing of land in river valleys this leads to inevitable silting and overgrowing of water bodies with aero-aquatic plants Baranovsky et al. As a result of all these developments, natural floodplain ecosystems changed considerably.

Meadows, woods and arable lands were flooded, hydrology and hydrochemistry were altered, the soils were impounded, the vegetation changed and initial high level of biodiversity decreased strongly Akinfiev ; Baranovsky and Aleksandrova ; Baranovsky et al.

For instance in the area of the Dniprovske reservoir, higher plant species were registered in the floodplain before construction works started.

Naturally diverse woodland ecosystems of floodplains Belgard changed into simple communities with reduced biodiversity. Forest ecosystems covering and surrounding Ukrainian floodplains in the past Nikolaenko , were largely degenerated or lost and replaced by meadows, pastures and tillage. The incessant destruction of the smaller rivers became one of the biggest regional environmental problems entailing sediment deposition in the larger rivers, summer bloom and fish kills caused by suffocation Baranovsky et al.

In the Dnieper basin the ecological conditions of the majority of small rivers are qualified either as catastrophic or as bad Zagubizhenko et al. Ecological changes include increased sedimentation and development of reeds Phragmities australis Cav. The management of floodplains in Ireland is still focused on flood alleviation, with the building of embankments and other flood defenses being a common approach.

There is also still an emphasis on the drainage of frequently flooded areas, rather than reinstating natural wetlands to slow down the rate of percolation of water through the system and therefore to slow down the rate at which the water reaches the rivers. The most common example of multifunctionality is likely the construction of weirs designed to ensure that they perform the role of water flow control while also facilitating the movement of fish and other aquatic species through the river system.

Small local-led initiatives funded by the EU Life programme have been the basis of several river restoration projects in Ireland which have sought to take a multifunctional approach to management. The main focus is to provide habitat for sea lamprey Petromyzon marinus , Atlantic salmon Salmo salar and European otter Lutra lutra. The project addresses multifunctionality by engaging with fisheries, farmers and the local community to achieve its multiple goals of improved water quality, locating alternative sustainable water sources for cattle, control of invasive species, and fostering a greater awareness locally of conservation issues relating to the river, its biodiversity and the ecosystem services that it supplies.

Both of these projects have occurred in Special Areas of Conservation designated for their river habitats and associated species. Funding was received in and the project is expected to lead to improved water quality and enhanced conditions for spawning salmonids, with benefits expected for overall biodiversity and recreational fishing to the area.

The Lough Melvin catchment management plan Campbell and Foy is another project that applies a multifunctional approach, with the main aim being to reduce nutrient levels within the catchment.

It has 22 recommendations covering impacts such as agriculture, forestry and wastewater from housing. Some of the most notable recommendations include i education programmes for landowners whose activities impact the environment, ii policies that restrict one-off housing in sensitive parts of the catchment, iii initiatives to deal with alien invasive species such as northern pike Esox lucio , iv screening of forestry operations in the catchment for appropriate assessment under Article 6 of the Habitats Directive, v a package of agri-environment measures for the Lough Melvin catchment, and vi active management of riparian forest buffer zones to reduce the impact of neighbouring clear-felling.

To our knowledge there is no Irish evidence for biodiversity effects of multifunctional floodplains. However, evidence for failure of monofunctional conservation projects is available Maher et al. In the Netherlands, the approach towards floodplains changed over the last two decades. The overall aim is to increase multifunctionality, with flood protection and increasing biodiversity being among the most important functions Fliervoet et al.

In the same period, water quality improved significantly due to the raising of environmental standards and international cooperation such as the International Rhine Committee. Through application of a mixed centralized—decentralized governance approach, the Room for River programme has dealt with governance pitfalls related to centralized planning approaches that previously impeded integrated water management Rijke et al.

It was a kind of new paradigm, which coincided also with the Ecological Network approach which was since leading for the Dutch conservation policy Van der Sluis et al. In and the water levels were extremely high, and a quarter of a million people had to be evacuated.

Extreme high river discharges are predicted to occur more frequently in the future and therefore it was decided to increase the discharge capacity of the rivers. In total, nine options are considered to enlarge riverbed and floodplains, including dyke relocation, depoldering, and water storage Fig. The approaches presented in this figure are rather advanced examples of eco-engineering, and are expected to have different impacts on multifunctionality, natural dynamics, and biodiversity Table 3.

Of the potential projects that were identified in the area of the Rhine and the Ijssel, 39 were selected Rijke et al. For the River Meuse, the Meuse Works Programme, was officially initiated in and scheduled for completion by The aims were similar to the ones for the Rhine: fewer floods, better navigability, a wider river bed and a more natural river valley.

In total, ha are to be converted to nature restoration areas, and 52 projects are or have been executed in the Meuse area Footnote 1 ; they focus on dyke improvement, tourism and grazing management. Nature restoration projects along the Meuse were executed from onwards Kurstjens and Peters The Meuse floodplains changed from an area which was mostly farmed or used for mineral extraction to a multifunctional area aimed at flood security, natural functions and recreation.

The extent of natural floodplain habitats along the Meuse increased from ha in to ha in Kurstjens and Peters , and the number of such areas increased from four to A strong increase in the riverine flora happened particularly in locations with sandy soils, where sand dynamics are a crucial factor. While increased dynamics also resulted in the loss of species that depend on stable situations, the overall impact was an increase in species diversity.

Mammal indicator species such as Eurasian beaver Castor fiber , European otter and European badger Meles meles returned. They had been absent from the rivers since the s, or extinct in Dutch territory in the case of the Beaver. For birds, the situation of pioneer species as well as species from softwood and hardwood forests and colony breeders improved significantly.

However, marshland and farmland birds have not recovered yet or are still declining, despite active restoration plans Kurstjens and Peters a.

Of the amphibian species the Great crested newt Triturus cristatus occurs along the different branches of the Rhine Creemers , and among reptiles, the Grass snake Natix natrix shows a positive trend along the natural floodplains of the Lower Rhine. The populations of fish of running water are increasing because of the improved water quality of the Rhine and the construction of side channels.

Even fish species which were extinct have returned, such as the Atlantic salmon, for which conservation plans were implemented and many rivers were made passable Van der Sluis et al.

Recovery of butterflies is slow; the two areas with the highest species density are the Blauwe—Kamer and the Duursche Waarden Online Ressource 1. The number of dragonflies has much increased due to the improved water quality, climate change and increased biotope diversity, especially in the Blauwe Kamer and the Duursche Waarden. Grasshoppers have also benefited.

For some species climate warming is a relevant factor in recovery Warren et al. In Germany, multifunctionality is, to a very limited extent, included in various legal regulations. For instance, the Federal Water Act demands water managers to preserve, protect and even improve natural habitat, to preserve and improve current and potential uses of water resources, thus to manage resources beyond water in a sustainable manner. In particular, conservation goals have increasingly been included in other sectoral laws.

Furthermore, several large projects have been carried out which tackled multiple aspects at a time, mostly flood protection and nature conservation, e. Emscher project, Isar in Munich. On a national level, the Federal Agency for Nature Conservation has financed restoration projects for about 15 years to enhance both nature conservation and flood protection.

The Flood Pulse Concept states that predictable seasonal floods are beneficial for riverine systems and can influence biotic composition, nutrient transport, and sediment distribution but unpredictable floods may be disruptive for aquatic organisms Junk et al. Additionally, many aquatic ecosystems have reduced resilience to future extreme events such as flooding due to human activities that include urban development and farming on floodplains, river flow disruptions, and pollution Woodward et al.

The specific effects of flooding on aquatic ecosystems and their services are not well understood, but the importance of flooding for maintaining ecological functions in rivers has been recognized Peters et al. Most of the research on flooding takes advantage of fortuitous events and thus often lacks pre-flood reference data Poff and Zimmerman This relatively sparse evidence on how flooding and changes in hydrology impact aquatic ecosystems drives a large amount of environmental flow management Acreman et al.

Using an ecosystem service approach can help advance our understanding of the impacts of flooding on aquatic ecosystems and how future changes in flood magnitude will change the availability of aquatic ecosystem services. People have taken advantage of various ecosystem services for over 10, years Fisher et al. There are many studies that evaluate the effects of disturbances on ecosystem services, but most of these studies focus on terrestrial systems and there are few that look at aquatic ecosystem services Grizzetti et al.

Furthermore, there are even fewer studies that integrate the effects of hydrologic changes Terredo et al. Aquatic ecosystems provide many services such as drinking water, soil formation, primary production, and areas for recreation or tourism, but flooding can impact the availability of these services. We expected to find that flood magnitude plays a role in determining whether aquatic ecosystem services are lost or gained following flood events. We expected that small floods would lead to gains in aquatic ecosystem services, while extreme floods would lead to losses.

If ecosystem services respond to small and extreme magnitude floods differently, then current flood mitigation strategies may be detrimental to aquatic ecosystem services. Common flood mitigation activities such as damming and flood barrier implementation restrict the occurrence of small floods but are often unable to mitigate extreme floods Alfieri et al.

In this study, we examined the societal pros and cons of various flooding events by evaluating their effects on aquatic ecosystem services. We used our current understanding of ecosystem services and flood impacts on aquatic ecosystems to identify gains and losses in ecosystem services resulting from flood events of different magnitudes. We completed a systematic literature review on a subset of 10 aquatic ecosystem services thought to be directly influenced by flooding to determine whether small versus extreme floods cause gains or losses in these services Table 1.

The ecosystem services included represent a variety of service types i. We also compared the influences of small versus extreme magnitude floods on each of the 10 ecosystem services to distinguish between normal often seasonal flooding and rare extreme events that may impact aquatic ecosystems differently. We hypothesized that small floods would enhance ecosystem service provisioning compared to large floods, which we expected would have more negative effects on ecosystem services.

Ultimately, our study can be used to inform effective flood protection strategies that can mitigate the undesirable consequences of flooding while preserving aquatic ecosystem services. Decision makers may use the demonstrated importance of small versus extreme floods for ecosystem services to better manage for variable flows, including small and occasional extreme floods.

Because ecosystem services are derived from well-functioning ecosystems, managing for ecosystem services may simultaneously benefit people and aquatic ecosystems. The Millennium Ecosystem Assessment MA aimed to address how ecosystem change can affect ecosystem services and their beneficiaries and to find a scientific way to ensure sustainable use and conservation of these services MA These frameworks and others typically focus on final services services that people use directly and emphasize economic valuation, which was not the goal of our analysis.

Additionally, none of these frameworks are widely used Nahlik et al. Therefore, we chose to use the MA framework to structure our analysis because it is commonly used to evaluate ecosystem services and is flexible enough to capture many types of services.

We used a group of 10 ecosystem services identified by the MA framework spanning the following four MA categories; 1 regulating services benefits resulting from the regulation of ecosystem processes , 2 provisioning services services that provide a product , 3 supporting services services that aid in the production of all other ecosystem services , and 4 cultural services nonmaterial benefits MA Table 1. Supporting services are ecosystem functions and processes, which aid in the production of other services Brauman et al.

For example, soil formation provides one of the materials necessary for agriculture, contributing to the provisioning service of food supply. Since the MA was completed, the ecosystem services concept has evolved and supporting services are now typically considered ecosystem functions rather than benefits or ecosystem services Haines-Young and Potschin However, we included supporting services in our analysis in order to capture a larger range of possible aquatic ecosystem responses to flooding.

In contrast, provisioning services provide a material product that can be harvested or collected and then traded in markets Brauman et al.

Regulating services regulate ecosystem processes, providing a suitable environment for people to live in Braat and de Groot Cultural services are also non-material goods.

They provide sensory experiences that enhance quality of life such as areas for recreation and tourism and aesthetic value. Ecosystem services can be assessed either by quantifying biophysical changes or by assigning a dollar value to those changes Braat and de Groot We used indicators of ecosystem service changes derived from variables measured in studies collected during our literature review to determine gains and losses in ecosystem services after flooding.

We found that a variety of indicators or variables were used to report changes in the same ecosystem service; therefore, we included as many commonly reported indicators as possible. Because each flooding event is context dependent e. Instead, we provide a general pattern rather than a quantitative change of ecosystem service changes in response to flooding. We performed a systematic literature review to locate existing research on the effects of flooding on ecosystem services.

We obtained published articles from Web of Science from to and summarized them. We focused upon the impacts of river basin flooding rather than flooding involving seawater intrusion or saltwater flooding, but studies included contained a variety of flood-generating mechanisms such as monsoons, cyclones, snowmelt, storm surges, and heavy precipitation.

We chose to use flood return interval to characterize floods as either small or extreme because it is commonly present in the published literature. Other flood characteristics such as duration and frequency are also important for determining the effects of flooding but were rarely reported in published literature and therefore not explicitly considered in this study.

This was a challenge because the impacts of small and seasonal floods are often not reported Douben Therefore, the analyses of extreme flood impacts on ecosystem services are more complete. We searched for each ecosystem service individually. Then, specific terms related to each indicator were added. We followed-up the initial literature search with searches aimed at finding additional studies on small floods. This increased the number of results returned during searches, but many studies were excluded because they did not report overbank flow or inundation, thus not allowing us to accurately characterize the flood.

All studies with abstracts containing information about a specific flood or storm event and a variable representing an ecosystem service were downloaded. We screened each of these studies one additional time to identify studies, which included a quantitative measure of the flood impact such as before and after measures of the same variable e.

Table 2. These initial literature results were augmented by further targeted searches on specific services and other work cited in the initially identified papers. This resulted in studies after the literature search given described constraints.

In general, the literature reported negative effects associated with flooding. Flooding is commonly perceived as detrimental and most studies tend to focus on the negative impacts of floods rather than the positive impacts. This bias may have skewed our results toward greater ecosystem service losses, but we were still able to identify ecosystem services which benefit from flooding.

Ecosystem service availability varied with flood magnitude Fig. Both small and extreme floods generally decreased the availability of most ecosystem services.

However, extreme floods caused a greater number of ecosystem service losses than small floods Table 3. Extreme floods were beneficial for groundwater and aquifer recharge and therefore were positive for these services. Small floods were important for improving access to food and recreation as well as beneficial for water regulation and primary production.

The impacts of floods on ecosystem services were also related to initial physical, chemical, and biological conditions within the ecosystem and its location. These complex interactions made it difficult to attribute changes in ecosystem services to specific flood events.

For example, post-flood changes in primary production varied because of temperature, light, and nutrient conditions. Additionally, there was some variation within individual ecosystem services which made assigning a negative, neutral, or positive outcome difficult.

However, we were able to identify many of the possible underlying mechanisms that were responsible for ecosystem service outcomes post-flood from reviewed literature Fig. Below we describe each ecosystem service and its connection to flooding in more detail.

Processes linking small and extreme floods to changes in aquatic ecosystem services. Hydrology is known to influence primary production by affecting water clarity, oxygen, pH, and nutrient concentrations Lindholm et al.

Floods may initially inhibit primary production while water is high but nutrients mobilized during storms may be held and processed in ecosystems later, when water levels return to normal Paerl et al. Small seasonal floods contribute nutrients to aquatic ecosystems and can stimulate primary production Junk et al. Increased primary production can then support aquatic food webs, providing a food source for consumers Alford and Walker However, larger floods can transport excessive nutrients and potentially stimulate excessive primary production i.

Recently, increases in primary production have been attributed to increased phosphorus P and nitrogen N loading associated with flood events Paerl et al. For example, flooding in the Lake Winnipeg catchment increased phytoplankton biomass and the phytoplankton community shifted to include more cyanobacteria McCullough et al.

Harmful algal blooms HABs such as those which occurred in Lakes Winnipeg and Erie cause several problems for people who rely on these water bodies for drinking water and recreation. HABs include cyanobacteria which produce toxins that must be removed from drinking water supplies Hitzfeld et al. HABs also lead to poor aesthetics, which adversely affect tourism and recreation activities, with detrimental impacts on local economies such as those around Lake Erie Watson et al. Primary production benefits aquatic ecosystems up to a certain tipping point, when HABs can dominate and negate these benefits Paerl et al.

Therefore, increased primary production post-flood is considered an ecosystem service net gain but if primary production is excessive then flooding results in a net loss. Additionally, if a flood event decreases primary production, then it is considered a net loss. Our literature review uncovered no consistent patterns of post-flood primary production responses.

Both increases and decreases in primary production after flooding were reported. One study reported higher gross primary productivity GPP after a small flood e. Lindholm et al. Uehlinger ; Uehlinger et al.

Chlorophyll a used as a surrogate for primary production concentrations were also observed as decreasing after small floods e. Rodrigues et al. Differential responses in primary production are likely the result of differences in nutrient supply, light penetration, and flushing rates of impacted ecosystems Paerl et al.

Additionally, post-flood increases in nutrient supply must occur simultaneously with sufficient light penetration to cause increases in primary production. Minor et al. The two studies reporting on the effects of extreme flooding on primary production also contained mixed results. Silva et al. In addition to providing nutrients, freshwater discharge resulting from flood events modulates the rate of flushing or water residence time of receiving waters.

If flushing rates exceed algal growth rates, large flood events could reduce algal biomass, regardless of nutrient enrichment Peierls et al. We therefore cannot consistently conclude whether flooding increases or decreases primary production and algal biomass since these indicators are highly dependent on other, interacting variables such as nutrient enrichment, water clarity, flushing rates, and grazing. However, the potential for large algal blooms occurs after flooding when nutrients are high and water residence time is long enough to allow blooms to form and accumulate Paerl et al.

Soil formation provides an essential service by regenerating river banks, wetlands, and flood-plain farmland. Flooding causes over bank flow and changes the rate of sediment deposition and erosional processes occurring between the river and floodplain Junk et al.

Flooding can cause river bank erosion and collapse, as well as upland erosion and incision, leading to landslides in areas with hillslopes and mountainous terrain Larsen and Montgomery which pose threats to people e. Kala Alternatively, flooding can improve soil formation by depositing sediment on floodplains, which recharges farmland soils and increases suitability for farming Ogbodo Therefore, the net positive or negative impacts of flooding on soil formation depend on where erosion and deposition occur and the volume of sediment transported.

The influence of a flood event on erosion and accumulation is related to the flow peak magnitude Julian and Torres Such re-deposition events are important in maintaining coastal forests and wetlands e. Nyman et al. Barbier et al. Therefore, soil erosion processes are spatially dynamic and the negative effects of erosion in certain locations, such as river banks or hill slopes, may enhance soil formation in other areas of a catchment, such as floodplains Pearson et al.

Such effects can be strongly exacerbated by land use practices, and over time, can lead to both improved farming locations and detrimental, even catastrophic flooding within the same river basin, as illustrated by the Yellow River catchment in China over the past years Rosen et al.

We found that extreme flooding caused substantial amounts of soil to be eroded in all studies. Another study reported over 1. Small floods also influence soil formation, although their effects are less dramatic than extreme events.

Some studies, such as one by Dewan et al. In addition to less erosion, small floods lead to less sediment accretion on river banks. Stromberg et al. They found that soil accretion generally increased with flood magnitude, but sediment accretion was similar in the 2 and 5-year floods compared to the year flood Stromberg et al.

Studies reporting the effects of multiple small events were more common than those reporting on single flood events. An example of a multiple-event study is by Leyland et al. Multiple-event studies are difficult to compare because some include an entire flooding season, while others include a few flood events.

Therefore, more studies on small individual flood events would be beneficial for assessing the impacts of small floods on soil formation.

Flooding is important for recharging underground water sources and recharge that results from flooding is especially beneficial during dry seasons when groundwater is the main source of freshwater in areas that experience pronounced wet and dry seasons Kazama et al.

In most cases, floodwaters are beneficial to recharge groundwater but this equation is changing with population growth. Demand for drinking water and water for irrigation will increase with population growth Singh et al. As a result, human populations deplete underground water stores through extraction for irrigation and, to a lesser extent, drinking water. The need for irrigation to supply water to crops will also likely increase in areas where global environmental change is expected to increase temperatures and change precipitation patterns and where people are converting natural land covers to agricultural land Taylor et al.

The effects of flooding on water regulation vary depending on floodplain conditions and natural hydrologic variability. For example, there is evidence that groundwater recharge is dependent on flood duration Benito et al. Additionally, inundation area determines how much floodwater infiltrates groundwater stores and larger inundation areas lead to more groundwater recharge. Therefore, flood mitigation strategies that reduce inundation area are detrimental to groundwater recharge processes Kazama et al.

However, groundwater levels that increase during flooding and extend above riverbeds or the soil surface can also contribute to more extreme flooding e. Gotkowitz et al. Groundwater flooding can last longer than riverine overbank flooding and possibly inundate basements, agricultural land, and roads Hughes et al. Therefore, it is optimal when groundwater is recharged but not to the point of overfilling during floods. In our review of past flooding events, groundwater recharge increased with flooding in all 13 studies.

Most studies reported that extreme floods contributed more water to underground stores than small floods, but one study showed that smaller floods contributed a disproportionately large amount of water to groundwater stores Aksoy and Wittenberg Extreme floods contributed high volumes of water to groundwater stores.

For example, an extreme flood increased the groundwater level by 0. Additionally, Wang et al. Small floods occurring seasonally were also capable of supplying substantial amounts of water.

For example, one seasonal flood increased groundwater level by more than 0. Therefore, both extreme, rare floods, and small floods occurring seasonally lead to increased water volume in underground water stores and improved water regulation.

Flood events have contrasting effects on water quality. The country assessments are the sole responsibility of the EEA member and cooperating countries supported by the EEA through guidance, translation and editing.

Software updated on 09 November from version Code for developers. Systems Status. Legal notice. Creative commons license. CMS login. Toggle navigation Skip to content. Advanced search A-Z Glossary. Error Cookies are not enabled. You must enable cookies before you can log in. Login Name. Forgot your password? You are here: Publications Why should we care about Briefing Why should we care about floodplains?

This website has limited functionality with javascript off. Please make sure javascript is enabled in your browser. Topics: Water and marine environment. Rivers are much wider than the channels we associate them with. The areas next to rivers, which are only covered by water during floods, are also part of the river system.

Known as floodplains, in their natural condition they are an important ecological part of this system: they filter and store water, secure both natural flood protection and the healthy functioning of river ecosystems, and help sustain the high biological diversity present there.

Natural water retention measures are cost effective and viable alternatives to structural flood protection. In addition, they support multiple ecosystem functions and services needed to achieve the objectives of several EU policies. Shifting the management focus towards natural retention measures represents a transition towards ecosystem based management and needs to be incorporated into river basin and flood risk management plans, conservation plans and climate change adaptation plans.

Restoration requires public support, investment and time. EU and national funding instruments are available to support restoration. Once implemented, natural water retention measures deliver valuable regulating ecosystem services and high quality cultural services. Identifiers Briefing no. Related content Sort by: Publishing date Title. Interactive charts Dashboard Tableau Pressures and impacts The WFD requires the identification of significant pressures from point sources of pollution, diffuse sources of pollution, modifications of flow regimes through abstractions or regulation and morphological alterations, as well as any other pressures.

In some cases, the pressure from several drivers, e. Further dashboards are available below. Publication European waters -- Assessment of status and pressures The main aim of EU water policy is to ensure that a sufficient quantity of good-quality water is available for both people's needs and the environment.

Blackwater Blackwater is a natural phenomenon where soil and sediment is washed into our waterways. Why the environment needs water The environment needs water to maintain important rivers and wetlands. Water management Common water management terms Complex terminology is used for water management across the Basin. Allocations, the states and the MDBA Each Basin state has different rules and requirements about how water is allocated.

Regular reports, Murray data and storages Summary of operations for the River Murray system including storage, flow and salinity data. Catchments Discover more about the Basin in your region by exploring the catchments in the Basin. Infrastructure managed by the MDBA Dams, barrages and weirs in the River Murray regulate water flows and help deliver of water to communities, irrigators and the environment.

Water markets and trade Trade is vital for irrigators by allowing flexibility in response to water availability. Community updates Reporting water quality issues Maintaining water quality is crucial to sustaining human life and a healthy, working Basin. Why did the fish deaths happen? Fish deaths in the Basin are caused by a combination of factors. Why don't we close the Murray river mouth?

The mouth of the River Murray is the only point in the Basin where the river system connects to the sea, creating a unique environment. Why is the Barmah Choke flooded when there's a drought? Water in the River Murray is often stored upstream and delivered to downstream users through the Barmah Choke, a narrow section of the river. How are dams being managed to reduce the impact of flooding?

The MDBA aims to make sure dam structures remain safe during floods. Why is erosion occurring in the River Murray and particularly through the Barmah Choke? Erosion of the riverbank has always been a feature of the River Murray. Subscribe to our email list to receive the latest media releases. Webinars Learn more about water management and river operations by joining our regular webinars.

Learn more about the annual conference and how to attend. Social media Connect with us. Find out more about a regional community forum near you.