Differences in flooding tolerance between species from two wetland habitats with contrasting hydrology: implications for vegetation development in future floodwater retention areas
Katarzyna BanachArtur BanachLeon P. M. LamersHans de KroonR. P. BennicelliAntoine J. M. SmitsEric J. W. Visser
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Abstract:
Plants need different survival strategies in habitats differing in hydrological regimes. This probably has consequences for vegetation development when former floodplain areas that are currently confronted with soil flooding only, will be reconnected to the highly dynamical river bed. Such changes in river management are increasingly important, especially at locations where increased water retention can prevent flooding events in developed areas. It is therefore crucial to determine the responses of plant species from relatively low-dynamic wetlands to complete submergence, and to compare these with those of species from river forelands, in order to find out what the effects of such landscape-scale changes on vegetation would be. To compare the species' tolerance to complete submergence and their acclimation patterns, a greenhouse experiment was designed with a selection of 19 species from two contrasting sites: permanently wet meadows in a former river foreland, and frequently submerged grasslands in a current river foreland. The plants were treated with short (3 weeks) and long (6 weeks) periods of complete submergence, to evaluate if survival, morphological responses, and changes in biomass differed between species of the two habitats. All tested species inhabiting river forelands were classified as tolerant to complete submergence, whereas species from wet meadows showed either relatively intolerant, intermediate or tolerant responses. Species from floodplains showed in all treatments stronger shoot elongation, as well as higher production of biomass of leaves, stems, fine roots and taproots, compared with meadow species. There is a strong need for the creation of temporary water retention basins during high levels of river discharge. However, based on the data presented, it is concluded that such reconnection of former wetlands (currently serving as meadows) to the main river bed will strongly influence plant species composition and abundance.Geological maps show where all the floodplains and coastal plains in Britain
are located and therefore the main areas at greatest risk of flooding. From this
information BGS has produced a map dataset called ‘geological indicators of
flooding’ (GIF).
To investigate the link between floodplain extent and extreme flooding events, BGS
carries out aerial surveys after a flood event disaster. This photographic collection
will be used to improve our understanding of floodplain processes and management
of floodplains. By extracting and digitising the actual extent of the flooding, these
images also provide first hand information to validate the GIF dataset.
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Maintaining the flood function of the floodplain is essential to ensuring that floodplains can perform their natural functions of flow conveyance and storage. The delineation of the floodplain based on its function during floods is a useful tool for determining the impact that development activity within the floodplain may have on flood behaviour. Breaking down the floodplain according to these functions identifies areas of the floodplain where flood behaviour is most sensitive to change. Traditionally in Australia, floodplains have been broken down into areas according to their hydraulic function. In most states, areas of the floodplain are classified as floodway or flow conveyance areas, flood storage areas or flood fringe areas. This hydraulic categorisation of the floodplain is typically applied to areas of the floodplain up to the Defined Flood Event (DFE), which historically has been assumed to correspond to the 1% Annual Exceedance Probability (AEP) event. However, consideration must also be given to flood function across areas of the floodplain between the DFE and the Probable Maximum Flood (PMF), which defines the true extent of the floodplain. This area is often neglected as it sits beyond the domain of typical planning controls, but may for some floodplains be an area of critical flood function due to risk and safety issues associated with the stability of buildings and people when exposed to floodwaters. Floodways are defined as those areas where a significant discharge of water occurs during floods. However, there are no specific procedures for identifying floodways or for defining their extent. The methodology for defining floodway extent is typically left to practitioners to determine. As a result, the outcomes are often subjective and can lead to conjecture due to the legal implications of land being classified as floodway. Over the last decade, there has been considerable advancement in the tools used to simulate flooding. Accessibility to improved and more detailed topographic data has also occurred, as has the capacity to more rigorously interrogate flood characteristics derived from computer modelling using this data. In particular, the increasing use of this data in 2D hydrodynamic models has allowed more meaningful representation of flood flow across floodplains. A range of data-sets such as depth, velocity, velocity-depth product, distribution of flow and unit stream power, can now be readily exported from flood models. This data can be combined with reliable topographic data to facilitate the hydraulic categorisation of floodplains, including the identification of floodways. At the same time, the modelling tools can be more easily adapted to test the impact of floodplain encroachment and confirm initial estimates of floodway corridors. This paper outlines a methodology that can be applied to all river and floodplain systems to determine floodway or flow conveyance area extent. It also documents examples of major and minor river systems where this methodology has been applied and considers the potential link between stability criteria and flow conveyance.
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By taking the Xichang Qionghai Lake Wetland Park as an example,the design theory and method for wetland environment protection of bird habitats were studied.Starting from type of birds and quantity,distribution characteristics,ecological habits and habitat requirements,the factors that constitute the wetland environment were analyzed and studied such as wetland plants,water,human factors etc.,the environmental factors that affect or fit birds to inhabit were found out.Under the conditions of full using the existing water landscape,plant disposition and wetland animal habitat other aspects of wetland habitat protection,the birds habitat protection design of wetland environment for the Qionghai Lake Wetland Park was optimized.
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Biological integrity
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Playa wetlands contribute to the biological diversity of the southern Great Plains, yet many are modified by current farming practices. We surveyed 12 farmed playa wetlands from 1998–99 to (1) document seasonal avian use of these habitats and (2) assess the performance of two rapid assessment techniques, the Habitat Assessment Technique and the Wetland Evaluation Technique. Thirty-six bird species were observed on farmed playa wetlands, 42% of which are dependent on wetland habitats. In contrast, only 5 species were observed on upland reference sites in 1999, and none were dependent on wetlands. Collectively, both rapid assessment techniques rated farmed playa wetlands as poor habitats because of the physical characteristics of study sites. Based on field observations and published work, we conclude that farmed playa wetlands provide habitat for many avian species and the rapid assessment techniques examined are unsuitable for assessing playa wetlands as avian habitat in Kansas.
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Numerous restoration campaigns focused on re-establishing species-rich floodplain meadows of Central Europe, whose species composition is essentially controlled by regular flooding. Climate change predictions expect strong alterations on the discharge regime of Europe's large rivers with little-known consequences on floodplain meadow plants. In this study, we aim to determine the effects of flooding on seedlings of different ages of four typical flood meadow species. To this end, we flooded seedlings of two familial pairs of flood meadow species of wetter and dryer microhabitats for 2 weeks each, starting 2, 4, 6, and 8 weeks after seedling germination, respectively. We show that a 2-week-flooding treatment had a negative effect on performance of seedlings younger than 6 weeks. Summer floods with high floodwater temperatures may have especially detrimental effects on seedlings, which is corroborated by previous findings. As expected, the plants from wet floodplain meadow microhabitats coped better with the flooding treatment than those from dryer microhabitats. In conclusion, our results suggest that restoration measures may perform more successfully if seedlings of restored species are older than the critical age of about 6 weeks before a spring flooding begins. Seasonal flow patterns may influence vegetation dynamics of floodplain meadows and should, therefore, be taken into account when timing future restoration campaigns.
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Floodplains are a fundamental source of multiple functions and services. Despite their various benefits, a dramatic reduction in floodplain areas has occurred in most large river systems over the last few centuries, and is still ongoing. Human modifications (such as river regulation, dam construction, and land use changes) due to economic growth, increasing population size, etc., were and still are drivers of major floodplain losses. Therefore, studies offering solutions for floodplain preservation and restoration are of great importance for sustainable floodplain management. This paper presents methods to identify active, former, and potential floodplains, and their application to the Danube River. We used hydraulic data, historical sources, and recent geospatial data to delineate the three floodplain types. Fifty hydraulically active floodplains larger than 500 ha were identified. According to our results, the extent of Danube floodplains has been reduced by around 79%. With the support of different representatives from the Danube countries, we identified 24 potential floodplains. However, the share of active and potential floodplains in relation to former floodplains ranges between 5% and 49%, demonstrating the huge potential for additional restoration sites. This analysis contributes to an understanding of the current and the past floodplain situation, increases awareness of the dramatic floodplain loss along the Danube, and serves as a basis for future floodplain management.
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The issues of forecasting damage caused by flooding of anthropogenically transformed territories in a river floodplain of a plain type are consideredbased on the case of the floodplain of the Pripyat River. A method of spatial analysis of the level of the territory usage and the depth/duration of floodingis proposed, the results of which are applicable in preparation of maps of the socio-economic risks associated with flooding, and in planning anti-floodmeasures.
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The explored 45 km tract of the Oka River floodplain is subdivided into three morphological areas: A hydrogeomorphological units formed by riverbed and floodplain flows (segment-ridge floodplains, parallel-ridge floodplains, flow-island floodplains); B hydrogeomorphological units formed away from riverbed and floodplain flows (smooth floodplains, leveled floodplains); C non-inundated sites (floodplain terraces). The article centers on structural and pattern peculiarities of loose sediments formation in different morphological areas, including buried soil horizons formed by alluvial sedimentation. The article treats some peculiarities of fluvial processes in the Oka river floodplain in the late Holocene, and focuses on the average rate of alluviation in the floodplain of the Oka in recent 27 years.
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River-floodplain systems are amongst the most productive—but often severely impacted—aquatic systems worldwide. We explored the ecological response of fish to flow regime in a large river-floodplain system by studying the relationships between (1) discharge and inundated floodplain area, with a focus on spatial and temporal patterns in floodplain lake connectivity, and (2) flood volume and fisheries catch. Our results demonstrate a non-linear relationship between discharge and floodplain inundation with considerable hysteresis due to differences in inundation and drainage rate. Inundation extent was mostly determined by flood volume, not peak discharge. We found that the more isolated lakes (that is, lakes with a shorter connection duration to the river) are located at higher local elevation and at larger hydrological distance from the main rivers: geographical distance to the river appears a poor predictor of lake isolation. Although year-to-year fish catches in the floodplain were significantly larger with larger flood volumes in the floodplain, they were not in the main river, suggesting that mechanisms that increase catch, such as increased floodplain access or increased somatic growth, are stimulated by flooding in the floodplain, but not in the river. Fish species that profit from flooding belong to different feeding guilds, suggesting that all trophic levels may benefit from flooding. We found indications that the ecological functioning of floodplains is not limited to its temporary availability as habitat. Refugia can be present within the floodplain itself, which should be considered in the management of large rivers and their floodplain.
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