Metacommunity Concepts Provide New Insights in Explaining Zooplankton Spatial Patterns within Large Floodplain Systems

Flood pulse related physical variables (FLOOD) can affect zooplankton community structure through local factors directly and can also influence through regional dispersal factors of metacommunity concepts indirectly. Therefore, we infer that spatial patterns of zooplankton communities could be related to metacommunity concepts and their importance may depend on the size of the aquatic/terrestrial transition zone (ATTZ). Herein, we explored the relative importance of limnological (LIMNO) and FLOOD variables in zooplankton community by analyzing data from 272 sites across three floodplain lakes in the middle reaches of the Yangtze River. Our results showed that the variation in the zooplankton community can be well explained by the LIMNO and FLOOD variables in all of the lakes under the low water level season. However, during the high water level season, neither LIMNO nor FLOOD can explain the spatial variances of zooplankton. Therefore, our results indicated that testing biogeographical theories and macroecological laws using zooplankton should consider temporal aspects of flood pulse. Furthermore, we noted that the number of explained variance by local variables is negatively correlated with the size of the ATTZ. Metacommunity concepts provide complementary insights in explaining zooplankton spatial patterns within large floodplain systems, which also provide a theoretical basis for ATTZ protection in floodplain management.

Vegetation characteristics control local sediment and nutrient retention on but not underneath vegetation in floodplain meadows

Sediment and nutrient retention are essential ecosystem functions that floodplains provide and that improve river water quality. During floods, the floodplain vegetation retains sediment, which settles on plant surfaces and the soil underneath plants. Both sedimentation processes require that flow velocity is reduced, which may be caused by the topographic features and the vegetation structure of the floodplain. However, the relative importance of these two drivers and their key components have rarely been both quantified. In addition to topographic factors, we expect vegetation height and density, mean leaf size and pubescence, as well as species diversity of the floodplain vegetation to increase the floodplain’s capacity for sedimentation. To test this, we measured sediment and nutrients (carbon, nitrogen and phosphorus) both on the vegetation itself and on sediment traps underneath the vegetation after a flood at 24 sites along the River Mulde (Germany). Additionally, we measured biotic and topographic predictor variables. Sedimentation on the vegetation surface was positively driven by plant biomass and the height variation of the vegetation, and decreased with the hydrological distance (total R2 = 0.56). Sedimentation underneath the vegetation was not driven by any vegetation characteristics but decreased with hydrological distance (total R2 = 0.42). Carbon, nitrogen and phosphorus content in the sediment on the traps increased with the total amount of sediment (total R2 = 0.64, 0.62 and 0.84, respectively), while C, N and P on the vegetation additionally increased with hydrological distance (total R2 = 0.80, 0.79 and 0.92, respectively). This offers the potential to promote sediment and especially nutrient retention via vegetation management, such as adapted mowing. The pronounced signal of the hydrological distance to the river emphasises the importance of a laterally connected floodplain with abandoned meanders and morphological depressions. Our study improves our understanding of the locations where floodplain management has its most significant impact on sediment and nutrient retention to increase water purification processes.

Meander floodplain management and stabilization of riverbank in urban region

The normalization of the Meander River in the past caused environmental problems, changed the river’s ecology, and required heavy maintenance such as stabilizing riverbanks with revetments, sheet piles and other constructions. Pesanggrahan River, located at Southern Region of Jakarta, Indonesia which has a meander channel at the border between the middle reach and downstream reach. The river was normalized at the end of the year 2012 with several modifications such as resection, realignment and cutting-off meandering bends. Analysis the effect of normalization consisting of meander cut-off and riverbank stabilization presented in this paper in term of the behaviour of sediment transport along the channel that has been normalized. HEC-RAS program is used to track the Pesanggrahan river flow from upstream to downstream before and after normalization. The Ackers-White equation used to calculate the amount of sediment for each section based on the change of the river section due to sediment motion after normalizing of the channel river. From the results of the study, it is proposed that a river naturalization or low impact development (LID) approach, such as floodplain management especially at the meander bend with riparian ecosystems that maintain stabilization at the riverbank also maintain habitat heterogeneity, is an important factor for the long-term survival of several rare and endangered species.

Flood of Ecology - Floodplain Habitation

<p>Larger and more devastating flood events are happening more frequently across the planet, but flooding is a natural occurrence for any river system. It is only due to human modification of the river system, through the removal of natural features and attempts at flood control, that creates flood hazards that cause damage to communities and ecosystems. Kapiti Coast’s terrain consisted, pre 19th century, of a mixture of dense coastal forests and extensive wetlands. The landscape has and always will be prone to flooding. With the addition of the expressway to the region, making it easier to travel to and from the capital Wellington, it is expected that the population of Kapiti will grow. But biodiversity may get lost, and flooding may become increasingly more frequent. How might new settlers learn to live with flooding and the constant risk that every time it rains it may cause damage to their homes or businesses? Can there be other benefits to floodplain management, such as biodiversity and recreation? The aim of this research is to investigate and develop strategies to aid in the settlement of floodplains so that biodiversity is improved, allowing people to live with floods and without the fear that flooding may cause damage. Specifically, the design-led research seeks to generate solutions that improve both flood awareness and flood protection along the Waikanae River. The design seeks to allow the river to express its own flow patterns, and then secondly, how settlement will work within that. It can then be a catalyst for settlement of floodplain areas along the edge of the river. This thesis will explore how ecology, rehabilitation and natural flood protection can be employed amongst an expanding urban context to create a new way of thinking about our rivers and mitigating the ever pressing issue of flooding.</p>

Flood of Ecology - Floodplain Habitation

<p>Larger and more devastating flood events are happening more frequently across the planet, but flooding is a natural occurrence for any river system. It is only due to human modification of the river system, through the removal of natural features and attempts at flood control, that creates flood hazards that cause damage to communities and ecosystems. Kapiti Coast’s terrain consisted, pre 19th century, of a mixture of dense coastal forests and extensive wetlands. The landscape has and always will be prone to flooding. With the addition of the expressway to the region, making it easier to travel to and from the capital Wellington, it is expected that the population of Kapiti will grow. But biodiversity may get lost, and flooding may become increasingly more frequent. How might new settlers learn to live with flooding and the constant risk that every time it rains it may cause damage to their homes or businesses? Can there be other benefits to floodplain management, such as biodiversity and recreation? The aim of this research is to investigate and develop strategies to aid in the settlement of floodplains so that biodiversity is improved, allowing people to live with floods and without the fear that flooding may cause damage. Specifically, the design-led research seeks to generate solutions that improve both flood awareness and flood protection along the Waikanae River. The design seeks to allow the river to express its own flow patterns, and then secondly, how settlement will work within that. It can then be a catalyst for settlement of floodplain areas along the edge of the river. This thesis will explore how ecology, rehabilitation and natural flood protection can be employed amongst an expanding urban context to create a new way of thinking about our rivers and mitigating the ever pressing issue of flooding.</p>

Salinity and food security in southwest coastal Bangladesh: impacts on household food production and strategies for adaptation

The rising salinity of land and water is an important, but understudied, climate change-sensitive trend that can exert devastating impacts on food security. This mixed methods investigation combines salinity testing with qualitative research methods to explore these impacts in one of the most salinity-affected regions in the world—the Ganges River Delta. Data collection in 2015 and 2016 undertaken in Bangladesh’s southwest coastal region and Dhaka consisted of 83 in-depth household and stakeholder interviews, six community focus groups, and salinity testing of 27 soil and 45 surface and groundwater samples. Results show that household food production is a multifaceted cornerstone of rural livelihood in the southwest coastal region, and virtually every component of it—from rice plantation and homestead gardening to livestock cultivation and aquaculture—is being negatively affected by salinity. Although households have attempted multiple strategies for adapting food production, effective adaptation remains elusive. At the community level, improved irrigation and floodplain management, as well as restrictions on saltwater aquaculture to abate salinity, are viewed as promising interventions. However, the potential of such measures remains unrealized on a broad scale, as they require a level of external resources and regulation not yet provided by the NGO and government sectors. This study elucidates issues of accessibility, equity, and governance surrounding agricultural interventions for climate change-related salinity adaptation, and its findings can help inform the community of organizations that will increasingly need to grapple with salinity in order to guarantee food security in the context of environmental change.

The Beautiful and the Dammed: Defining Multi-Stressor Disturbance Regimes in an Atlantic River Floodplain Wetland

Natural hydrological fluctuations within river floodplains generate habitat diversity through variable connections between habitat patches and the main river channel. Human modification of floodplains can alter the magnitude and frequency of large floods and associated sediment movement by interrupting these floodplain connections. The lower Wolastoq | Saint John River and its associated floodplain wetlands are experiencing anthropogenic disturbances arising from climate change, increased urbanization in the watershed, changing upstream agricultural landscape practices, and, most notably, major road and dam construction. By comparing digitized aerial images, we identified key periods of change in wetland extent throughout an ecologically significant component of the floodplain, the Grand Lake Meadows and Portobello Creek wetland complex, with significant erosion evident in coves and backwater areas across the landscape following dam construction and significant accretion around the Jemseg River following highway construction. Connectivity and hydrological regime also influenced other habitat components, namely nutrients and metals retention, as well as the composition of the local macrophyte community. These findings address two key aspects of floodplain management: (1) understanding how hydrological alteration has historically influenced floodplain wetlands can inform us of how the ecosystem may respond under future conditions, such as climate change, and (2) the mechanisms by which habitat diversity and disturbance regimes filter biological communities, with the potential for patches to host a rich biodiversity continuously supporting critical ecosystem functions.

Vegetation characteristics control sediment and nutrient retention on but not underneath vegetation in floodplain meadows

Sediment and nutrient retention are essential ecosystem functions that floodplains provide and that improve river water quality. During floods, the floodplain vegetation retains sediment, which settles on plant surfaces and the soil underneath plants. Both sedimentation processes require that flow velocity is reduced, which may be caused by the topographic features and the vegetation structure of the floodplain. However, the relative importance of these two drivers and their key components have rarely been both quantified. In addition to topographic factors, we expect vegetation height and density, mean leaf size and pubescence, as well as species diversity of the floodplain vegetation to increase the floodplain's capacity for sedimentation. To test this, we measured sediment and nutrients (carbon, nitrogen and phosphorus) both on the vegetation itself and on sediment traps underneath the vegetation after a flood at 24 sites along the River Mulde (Germany). Additionally, we measured biotic and topographic predictor variables. Sedimentation on the vegetation surface was positively driven by plant biomass and the height variation of the vegetation, and decreased with the hydrological distance (total R2=0.56). Sedimentation underneath the vegetation was not driven by any vegetation characteristics but decreased with hydrological distance (total R2=0.42). Carbon, nitrogen and phosphorus content in the sediment on the traps increased with the total amount of sediment (total R2=0.64, 0.62 and 0.84, respectively), while C, N and P on the vegetation additionally increased with hydrological distance (total R2=0.80, 0.79 and 0.92, respectively). This offers the potential to promote sediment and especially nutrient retention via vegetation management, such as adapted mowing. The pronounced signal of the hydrological distance to the river emphasises the importance of a laterally connected floodplain with abandoned meanders and morphological depressions. Our study improves our understanding of the locations where floodplain management has its most significant impact on sediment and nutrient retention to increase water purification processes.