Resilience of Amazonian forests : the roles of fire, flooding and climate
Monteiro Flores, B. - \ 2016
Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Milena Holmgren Urba; Jose de Attayde. - Wageningen : Wageningen University - ISBN 9789462578876 - 128
forests - resilience of nature - fire - flooding - floods - climate - floodplains - vegetation - amazonia - bossen - veerkracht van de natuur - brand - inundatie - overstromingen - klimaat - stroomvlakten - vegetatie - amazonia
The Amazon has recently been portrayed as a resilient forest system based on quick recovery of biomass after human disturbance. Yet with climate change, the frequency of droughts and wildfires may increase, implying that parts of this massive forest may shift into a savanna state. Although the Amazon basin seems quite homogeneous, 14% is seasonally inundated. In my thesis I combine analyses of satellite data with field measurements and experiments to assess the role of floodplain ecosystems in shaping the resilience of Amazonian forests.
First, I analyse tree cover distribution for the whole Amazon to reveal that savannas are relatively more common on floodplains. This suggests that compared to uplands, floodplains spend more time in the savanna state. Also, floodplain forests seem to have a tipping point at 1500 mm of annual rainfall in which forests may shift to savanna, whereas the tipping point for upland forests seems to be at 1000 mm of rainfall. Combining satellite and field measurements, I show that the higher frequency of savannas on floodplain ecosystems may be due to a higher sensitivity to fire. After a forest fire, floodplains lose more tree cover and soil fertility, and recover more slowly than uplands (chapter 2).
In floodplains of the Negro river, I studied the recovery of blackwater forests after repeated fires, using field data on tree basal area, species richness, seed availability, and herbaceous cover. Results indicate that repeated fires may easily trap blackwater floodplains in an open-vegetation state, due the sudden loss of forest resilience after a second fire event (chapter 3).
Analyses of the soil and tree composition of burnt floodplain forests, reveal that a first fire is the onset of the loss of soil fertility that intensifies while savanna trees dominate the tree community. A tree compositional shift happens within four decades, possibly accelerated by fast nutrient leaching. The rapid savannization of floodplain forests after fire implies that certain mechanisms such as environmental filtering may favor the recruitment of savanna trees over forest trees (chapter 4).
In chapter 5, I experimentally tested in the field the roles of dispersal limitation, and environmental filtering for tree recruitment in burnt floodplain forests. I combine inventories of seed availability in burnt sites with experiments using planted seeds and seedlings of six floodplain tree species. Repeated fires strongly reduce the availability of tree seeds, yet planted trees thrive despite degraded soils and high herbaceous cover. Moreover, degraded soils on twice burnt sites seem to limit the growth of most pioneer trees, but not of savanna trees with deeper roots. Our results suggest a limitation of forest trees to disperse into open burnt sites.
The combined evidence presented in this thesis support the hypothesis that Amazonian forests on floodplains are less resilient than forests on uplands, and more likely to shift into a savanna state. The lower ability of floodplains to retain soil fertility and recover forest structure after fire, may accelerate the transition to savanna. I also present some evidence of dispersal limitation of floodplain forest trees. Broad-scale analyses of tree cover as a function of rainfall suggest that savannas are likely to expand first in floodplains if Amazonian climate becomes drier. Savanna expansion through floodplain ecosystems to the core of the Amazon may spread fragility from an unsuspected place.
Community based fish culture in the public and private floodplains of Bangladesh
Mahfuzul Haque, A.B. - \ 2015
Wageningen University. Promotor(en): Leontine Visser, co-promotor(en): M.M. Dey. - Wageningen : Wageningen University - ISBN 9789462574533 - 166
stroomvlakten - visteelt - ontwikkelingsstudies - ontwikkelingseconomie - samenleving - huishoudens - bangladesh - zuid-azië - floodplains - fish culture - development studies - development economics - society - households - bangladesh - south asia
Seasonal floodplains are water bodies that retain water for 5-6 months during which they are suitable to grow fish and other aquatic animals. Out of 2.8 million ha of medium and deep-flooded areas, about 1.5 million ha are estimated to be suitable for Community-Based Fish Culture (CBFC). WorldFish had undertaken a five-year interdisciplinary action research project from 2005-2010 with the overall aim of enhancing the productivity of seasonally occurring floodwaters for the improved and sustained benefit of the livelihoods of the poor. My involvement in this project was as PhD Scholar from 2007-2009 for understanding the different and complex institutional arrangements and its overall impact of governing Community-Based Fish Culture in seasonal floodplains for the sustainable use and maximization of benefits to the targeted people of Bangladesh.
Six seasonal floodplains in different areas of Bangladesh were selected under the action research project implemented by the Department of Fisheries in collaboration with the Bangladesh Agricultural Research Council and the Bangladesh Fisheries Research Institute. For the action research which is the subject of this thesis, three seasonal floodplains were selected in the Brahamaputra, the Padma and the Teesta River Basins located at Mymensingh, Rajshahi and Rangpur districts, respectively. Another three floodplains were selected as control sites in the same river basins located near to the projects sites. The control sites were included in the economic study (Chapters 4 and 5) only. All the six floodplains belong to two types of ownership categories: public floodplains surrounded by private lands.
My thesis is broadly divided into a sociological and an economic part, mainly because of methodological differences. Chapter 2 and Chapter 3 discuss the institutional arrangements and the power and decision-making process of Community-Based Fish Culture management. Chapter 4 addresses the overall economic impact of technical and institutional arrangements of fish culture at both floodplain and household levels. We here employed a random effects model to estimate the impact of participation on fish income. Finally, in Chapter 5 the economic impact of community-based fish culture on expenditure inequality was measured at household level.
In the sociological part, three project floodplains covered the different institutional arrangements for managing the floodplains and maximizing their benefits to different classes of beneficiaries. Power relations between the various key actors or stakeholders were assessed who were directly or indirectly involved in the floodplain, and decision making processes in co-management practices were also studied at different institutional levels. Sociological research methods and techniques including semi-structured interviews, Focus Group Discussions, informal discussions with key informants, and
For the economic analysis of Chapter 4 and Chapter 5, three project floodplains and three control floodplains were selected for comparing the impact of the intervention at beneficiary level and also community level. Household survey data includes a baseline survey on socioeconomic information, three months monitoring on seasonal and monthly basis at community and household levels, as well as an assessment of the floodplains’ natural resource systems. The seasonal survey covered the changes in input use for crop production, changes in quality of output from the agricultural land and the effects of the intervention on crop production. A monthly survey on the 1st and 15th day of the month was conducted to capture the household consumption pattern, especially the frequency and quantity of fish and meat consumption.
Chapter 2 improves our understanding of the complex institutional relationships governing Community-Based Fish Culture in seasonal floodplains in Bangladesh. Formal institutional linkages between DoF, WorldFish Center and the Bangladesh Agricultural Research Council (BARC) played a key role in ensuring success. DoF is a government institution with establishments at different administrative levels. Institutional embedding of DoF through the Fishers Cooperatives (FMC) as implementing institutions appeared highly instrumental. Large numbers of people, including landless poor seasonal fishers, professional landowning fishers, and non-fishing landowners benefited from the successful implementation of the CBFC activities in the floodplains. The outcomes demonstrate a significant increase in income to all classes of beneficiaries through income sharing derived from their involvement in the fisheries cooperatives and fish culture.
In case 2 and case 3 the floodplains under private ownership privately owned land is inundated during the monsoon season; these floodplains are similar in size, with comparable percentages of beneficiaries and similar numbers of communities surrounding the floodplains. However, the distribution of beneficiaries among the classes differs with more landowners than landless seasonal fishers benefitting. FMCs normally allow these non-members to access the floodplains, but only to harvest un-stocked fish using local gears, considering the importance of fishing to their livelihood. This means that the CPR character of the management by the FMCs shows a certain permissiveness or permeable boundary regarding landless non-members under strict spatial and temporal conditions. Regulation and conservation thus guarantee the availability of un-stocked small fish in the floodplains with a high catch by artisanal gears which results in higher incomes and related benefits to the poorer households. Households who own land or ditches in the floodplains do not depend on un-stocked fish as they can have ponds to trap and harvest fish obtained in the wild. Additionally, during the dry season, they may use land in lowland areas for crop production.
Case 1 of the public floodplain surrounded by private lands differs most from the private floodplain cases. Here, the public area is leased out to fishers during the monsoon, including the private land owned by the affluent and politically influential stakeholders. The floodplain is larger than in the other two cases, but both the percentages of landless fishers and of landowners are lower, making the class of the landowning professional fishers the majority among the beneficiaries.
Generally, the rules and regulations that apply to public and privately owned floodplains are written down in a Memorandum of Understanding between DoF and the individual FMC’s in a non-judicial construction. In their regular meetings the FMCs also document the everyday practices of the rules related to fish culture and management in the minutes that are distributed among its members. It appears that in the three cases, comparable rules and regulations for fish culture are applied to the public and to the private floodplains in operational rules, collective choice rule and constitutional rule.
Benefit sharing of the fish production from the floodplains was agreed at the start of project activities by all stakeholders, but their commitment varied between the classes of beneficiaries and across the cases. A significant increase of income for different stakeholders was derived from their involvement in fish culture. In the public floodplain fishers received around 40% of net income increase and the landowners received almost 38% of net income increase, as they had to pay the lease money for the floodplain. But in private floodplain all classes of stakeholders deposited around 25% of their net income in a revolving fund. The fishers group got their income from the final harvesting of fish as they received 50% of the price of the harvest of un-stocked fish and 10-15% of the stocked fish. The landowners received 45-50% of income according to their land. The landless seasonal fishers had open access to the non-stocked fish during the monsoon. Finally, the users of the public as well as the private floodplains contributed a small portion of their income to social work, like the building of a mosque or a Hindu temple.
Chapter 3 firstly assessed the power relations between the various key actors or stakeholders who were directly or indirectly involved in floodplain fisheries in the three sites. Secondly, their shifting power relations and decision making process in co-management practices were studied in the different institutional contexts of the three research sites during WorldFish project intervention. Instead of merely listing the institutions involved, we studied the actual power practices and decisions making processes between the stakeholders in the three cases to gain insight in the different governance models used in CBFC in Bangladesh. Existing co-management arrangements are characterized by unequal power distribution among the different actors, often resulting in the marginalization of the professional fishers and the landless poor fishers. I differentiated between two types of power in the management of floodplain aquaculture and stakeholder involvement, namely a) the power to create rules and decision making procedures, and b) the power to resolve disputes and ensure compliance. The Floodplain Management Committee (FMC) reviews the rules and regulations formulated by the government to complement the vision and roles of the institution, and if there is a need, modify them. Rules and regulations governing access to the public and privately owned floodplains were developed by the Department of Fisheries (DoF) and the FMC. A similar set of rules and regulations was applied to the public and the privately owned floodplains for fish culture. Most of the rules were derived from the national fisheries law. The rules and regulations that were applied to the floodplain were written down in a Memorandum of Understanding between DoF and FMC. Examples are rules and regulations about membership, leadership, boundary and access, allocation, penalties, input, and conflict resolution that were enforced for the management of community based-fish culture.
Magistrate courts at local level in Bangladesh have the power to decide on penalties for offenders in case of violation of the Government Fisheries Act of 2010 (DoF 2013) in the management of fisheries and aquaculture including the floodplain; a range of penalties is stipulated in the Offences and Penalties paragraph of the Act. In addition, in the case of both public and private floodplains, leaders of customary organizations have the authority and power to confiscate illegal nets and penalize offenders by charging monetary fines.
Governance in the context of Community-Based Fish Culture (CBFC) management addresses the dominancy of the land-owning group, informal sets of norms and traditions, and the social network and power relationships between stakeholders. In the public floodplain governance processes resulting in the formation of a responsive, accountable leadership and representative membership appeared vital for the success of CBFC. But, the establishment of successful CBFCs in public floodplains demands continuous institutional support from agencies such as the Department of Fisheries, because an increase in production and income also increases the risk of elite capture, and the possibility of an exploitative. In the private floodplain, there was no specific governance system in place to manage access and use of the floodplains during the wet season, as opposed to the dry months when the lands of the floodplain could be used by individual households for crop production. Thanks to greater accountability of the leaders, and more equal representation of the different stakeholders including active leadership and a supporting role of DOF, leadership problems were few and easily solved. Downward accountability was well established in addition to many efforts by the project.
Chapter 4 examined the overall impact on households involved through the WorldFish project in community-based fish culture in seasonal floodplains, particularly with respect to fish production, consumption, and income generation. Qualitative as well as quantitative methods were deployed to examine the impact of Community-Based Fish Culture starting with a conceptual framework as to how positive impacts take effect. The overall fish production in the floodplains of the project appeared to have increased 274%. Due to project intervention introducing fish culture, 43% of the farmers used floodplain water to meet up irrigation needs instead of ground water and rice production increased by 18.9% for dry-season (Boro) rice and 28.9% for wet-season (Aman) rice in the project floodplain areas.
Increased income is an important economic incentive for the expansion of community-based fish culture in Bangladesh. Over that period, average income from fish production increased to USD 240 for all beneficiaries involved in the project, which is 237% higher than the income of beneficiaries in the control group. Results of the random effects model show that project-involved households significantly increased their fish income compared to the households of the control sites. Furthermore, total household income increased to about USD 175 per household for those who participated in the WorldFish project.
Fish availability increased in the project area from July to December. During these months approximately 68%-75% of the total fish consumption needs of the project beneficiaries could be fulfilled by the newly introduced fish culture in the floodplains. The consumption of nutritional food shows that per capita fish consumption of households in the project sites increased from 1.26 kg per capita per month in the baseline year to 2.31 kg per capita per month in 2009.
Apart from the direct effect on household income and food consumption, CBFC intervention also created the opportunity for employment, backward linkage, and access to market to sell harvested fish. Indirect benefits of the community based fish culture include reduced conflict; improved social capital and greater cooperation in the community.
Expenditure is a better measurement of welfare than income where most of the people are poor and struggle for food. In this study I therefore used data on expenditure instead of income. The results in Chapter 5 show that the CBFC project had a positive and significant impact on food expenditure, as well as on non-food (other basic needs) and overall total expenditure. The impact of CBFC on household expenditure and expenditure inequality was measured by using Propensity Score Matching (PSM) method and Gini decomposition. Results revealed that the overall average food expenditure per year per household (for panel estimation) increased due to participation in the CBFC project from USD 93 to USD 141. Project participants were able to spend significantly more on food compared to non-participants. In addition, expenditure on food was increasing year by year. Moreover, participant households were capable to spend more compared to non-participants on non-food items like cloth, health, education, housing, transport etc. (from USD 45 to USD 74 per year). This non-food expenditure also gradually increased per year. Finally, total household expenditure of CBFC project participants was between USD 134 and USD 215 per year higher than the total expenditure of control households, which implies a better livelihood of the households involved in the project.
Gini index of total expenditure was found to be 0.34 and 0.40 for the CBFC project and control households respectively, which indicate that expenditure was equally distributed among households, but that it is more equally distributed among the CBFC households as compared to the control households. The expenditure inequality difference between the CBFC project and the control sites was 0.06, which implies that the CBFC management system helped to distribute total expenditure more equally among the surrounding communities.
For better management of the floodplain beels, the government may apply a similar policy for better utilization of the resources and for the economic benefits of the beneficiaries. Accountability, sustainable management of the floodplains, proper marketing of fish and equity in the distribution of benefits of the floodplains have proven to increase the productivity and ensure the accessibility of the poor and landless farmers, as long as elite capture is controlled.
Taking all CBFC project lessons into consideration, the Bangladesh government could indeed make some changes to their floodplain /wetland policy in order to accommodate the poor fishers and the landless poor. Policy (re)formulation may be needed for the dissemination of the CBO-based fish culture approach to scale-up its impact. In order to establish the rights of the CBOs (under the leadership of fishers) there is a need for modification of the policy of leasing of public floodplains. The major issues to be included are to bring private and public floodplains under CBO management; to secure government support for the registration of the CBOs and the strengthening of the institution; to guarantee that CBOs obtain long term (10-15 years or more) lease of the public areas of the floodplains as priority; to support small infrastructure constructions in the outlet and inlets of the floodplains; and to develop a functional model for the scaling-up (influencing policy) and scaling-out of the CBO fish culture approach in Bangladesh.
To assess the effectiveness of the scaling-up of the innovation in Community-Based Fish Culture in public and private floodplains, using a CBO to CBO approach will have to be developed with the support and facilitation from formal institutions. This will be considered as the subject of future research.
Interactions between land use and flood management in the Chi River Basin
Kuntiyawichai, K. - \ 2012
Wageningen University. Promotor(en): E. Schultz; S. Uhlenbrook. - [S.l. : S.n. - ISBN 9789461732491 - 213
hoogwaterbeheersing - overstromingen - waterbeheer - landgebruik - rivieren - stroomvlakten - watervoorraden - wiskundige modellen - thailand - flood control - floods - water management - land use - rivers - floodplains - water resources - mathematical models - thailand
The damages and hardships caused by floods and flooding remain an issue and are continuously increasing in the Chi River Basin, Thailand. It is difficult to make an accurate assessment of the costs and consequences associated with floods. However, flood hazards can also be seen as an opportunity, a chance to correct possible flaws and ambiguities in the flood management.
The Chi River system cannot handle the regularly occurring floods, consequently, flooding of the low-lying areas occurs on a regular basis. Therefore, an integrated flood management framework needs to be developed to minimize the negative effects of floods of different magnitude. In response, a hydrological model (SWAT) and a hydraulic (1D/2D SOBEK) model were integrated to simulate floods in detailed way and to analyse the current system. A reliable simulation of the river flows and inundated areas is an essential component of a holistic flood management plan.
The developed modelling framework enabled to analyse the impact of different structural measures such as river normalisation, green river (bypass), and retention basin. In addition, non-structural measures including reservoir operation and spatial land use planning were assessed in their capability to protect people and valuable infrastructure. For each measure, several possible scenarios were tested and evaluated based on economic and technical efficiency criteria to determine the most promising and efficient scenario. However, effective interventions may involve a judicious combination of flood mitigation approaches, rather than reliance on a stand-alone solution. A truly optimum combination of aforesaid measures was then chosen since it could considerably reduce flood extent and its damage.
Finally, the study illustrates the effects of land use changes on floods, which indicated little or no significant potential impact on flood regime at river basin level, but rather at sub-basin scale. This finding is important for a better understanding of the scale and direction of impacts of developments in the future. Integrated land use planning was shown to be an essential component of a comprehensive flood management framework.
Leren van de Wolga; vloedvlaktes blijken belangrijk voor vis
Nagelkerke, L.A.J. - \ 2011
Visionair : het vakblad van sportvisserij Nederland 20 (2011). - ISSN 1569-7533 - p. 16 - 19.
stroomvlakten - vissen - habitats - rusland - floodplains - fishes - habitats - russia
Eind 2007 verscheen in Visionair een artikel over een uniek onderzoek naar de relatie tussen vloedvlaktes en vis in de Russchische Wolga. Inmiddels is de eerste fase succesvol afgesloten. De onderzoeksresultaten bieden een schat aan informatie over de biologie en het beheer van riviervissen.
Floods and fish : recruitment and distribution of fish in the Volga River floodplain
Górski, K. - \ 2010
Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Leo Nagelkerke; Erwin Winter. - [S.l. : S.n. - ISBN 9789085858157 - 223
rivieren - stroomvlakten - overstromingen - vissen - populatie-aanwas - distributie - populatiedynamica - visbestand - rusland - visserijbiologie - hydrogeologie - aquatische ecosystemen - rivers - floodplains - floods - fishes - recruitment - distribution - population dynamics - fishery resources - russia - fishery biology - hydrogeology - aquatic ecosystems
Natural river floodplains are among the most diverse and productive ecosystems on Earth and provide key habitats for foraging, spawning and as a nursery for many riverine fish species. Periodic flooding plays a principal role in the ecological processes in floodplain systems resulting in high productivity and diversity, as formulated in the Flood Pulse concept (FPC, a major conceptual framework for understanding the hydro–ecological processes operating in river-floodplain systems). However, little progress has been made in exploring the FPC over larger spatial scales due to lack of empirical data. The Volga-Akhtuba floodplain (Russian Federation) is still relatively undisturbed, while in Europe and North-America about 90% of floodplains have effectively been lost. This thesis provides a quantitative assessment of the FPC by (1) analyzing flood pulse dynamics in response to changes in river flow regime on various spatial and temporal scales and (2) relating these to recruitment success of riverine fish species that use the floodplain; and (3) identifying the hydro-geomorphic variables that are most involved shaping fish abundance and distribution in the floodplain. The results obtained demonstrate that the flood pulse magnitude in the lower Volga has noticeably decreased due to damming of the Volga upstream from the Volga-Akhtuba floodplain. Still, in spite of this hydrological control, considerable year-to-year variation in flood magnitude and timing has remained. Therefore fish populations in the floodplain still depend on variations in the year-to-year flow regime. Moreover, spring temperature and its match with flooding control the recruitment of young fish at the end of the growing season. However, the main sources of spawning stocks in the large-scale Volga-Akhtuba floodplain originate from local floodplain populations and not from the main river channels. Spatial heterogeneity of hydro-geomorphic attributes of the floodplain water bodies is highly significant for structuring fish abundance and distribution in the floodplain. Therefore, even under changing environmental and social circumstances, it is essential to preserve flood dynamics, which is fundamental not only for fish recruitment success but also governs fish distribution and diversity in the floodplain.
Nematode-based risk assessment of mixture toxicity in a moderately polluted river floodplain in The Netherlands
Vliet, P.C.J. van; Goede, R.G.M. de - \ 2008
Science of the Total Environment 406 (2008)3. - ISSN 0048-9697 - p. 449 - 454.
stroomvlakten - zware metalen - nematoda - rivieren - indicatoren - graslanden - verontreiniging - toxiciteit - gelderland - land van maas en waal - waal - floodplains - heavy metals - nematoda - rivers - indicators - grasslands - pollution - toxicity - gelderland - land van maas en waal - river waal - soil - sensitivity - communities - cadmium - metals - forest
Heavy metal polluted soils usually contain mixtures of different metals, whereas legislation is derived from concentrations of individual metals. The mixture toxicity of the Dutch floodplain Afferdensche and Deestsche Waarden was estimated to be high (msPAF ranged from 67¿94%). Analyses of nematode community based bioindicators (Maturity Index, taxonomic diversity, trophic groups, multivariate analysis, DoFT-sentinels) were used to determine the ecological effects of the mixture toxicity in the floodplain soil. None of the indices indicated direct effects of heavy metals on the nematode community. This can be explained by the high adsorption of heavy metals on organic matter and clay particles resulting in a low bioavailability, and questions the estimation of the toxicity based on total concentrations of heavy metals in such environments. The nematode fauna showed great seasonal variation, which most probably was related to the temporal inundation of the floodplain.
Aeolian and fluviolacustrine landforms and prehistoric human occupation on a tectonically influenced floodplain margin, the Méma, central Mali
Makaske, B. ; Vries, E. de; Tainter, J.A. ; McIntosh, R.J. - \ 2007
Netherlands journal of geosciences 86 (2007)3. - ISSN 0016-7746 - p. 241 - 256.
eolische afzettingen - geomorfologie - geologische sedimentatie - rivieren - landschap - stroomvlakten - mali - aeolian deposits - geomorphology - geological sedimentation - rivers - landscape - floodplains - mali - niger - holocene - africa
The Méma is a semi-arid region in central Mali with a rich archaeological heritage indicating the former existence of large urban settlements. The archaeological data suggest millennia of occupation history of the Méma preceding relatively sudden abandonment by the 14th or 15th century AD. Population numbers have remained low since then and today's human presence in the area is sparse and largely mobile. Geomorphologically, the Méma can be characterized as a graben hosting various generations of aeolian landforms and (presently mostly dry) interdunal channels and lakes, linked to the neighbouring Inland Niger Delta floodplain. Given this setting, and the variability of the Sahelian climate, climatic contributions to the region's sudden abandonment are likely. A geomorphological survey of the region, and interpretation of the observed geomorphological record in terms of climatic history, aimed at providing a basis for understanding the intensive occupation and subsequent abandonment of the Méma. The results of this study underscore dramatic Holocene climatic variability, leading to the region's present geomorphological diversity, but also suggest that neotectonic movements constitute an important additional cause of regional desiccation. Both may have encouraged prehistoric people to abandon the Méma after a long period of occupation.
Bioaccumulation of persistent organic pollutants from floodplain lake sediments: linking models to measurement
Moermond, C.T.A. - \ 2007
Wageningen University. Promotor(en): Bart Koelmans, co-promotor(en): J.J.G. Zwolsman. - [S.l.] : S.n. - ISBN 9789085047056 - 192
sedimentmaterialen - stroomvlakten - ecotoxicologie - aquatische ecosystemen - bioaccumulatie - persistente organische verontreinigende stoffen - sedimentary materials - floodplains - ecotoxicology - aquatic ecosystems - bioaccumulation - persistent organic pollutants
The main research questions of this research were (1) what is the extent and nature of bioavailability of sediment-bound polychlorobiphenyls (PCBs) and polyaromatic hydrocarbons (PAHs) and (2) what are the effects of lake ecosystem structure on fate and bioaccumulation of PCBs and PAHs. Fast-desorbing fractions in the sediment of floodplain lakes were estimated by the 6-h Tenax-extractable fractions with a correction factor. These fractions varied between 1 and 40% and did not show a clear trend with log KOW. This means that contaminants in these sediments were available, but to a smaller extent than total concentrations would suggest. The 6-h Tenax extractable concentration often correlated better with bioaccumulation than the total extractable concentration in sediment. Despite the reduced availability, benthivorous fish and invertebrates in floodplain lakes still rapidly accumulated substantial amounts of PCBs. PAHs were accumulated relatively less because PAHs were relatively less available than PCBs due to their stronger sorption to carbonaceous materials, also referred to as soot or black carbon. For fish, metabolic transformation caused even lower PAH concentrations. Contaminants that have been present in the sediment for longer periods of time (years to decades), were less available for Tenax extractions as well as for uptake by biota in different parts of the food web than contaminants that were recently added. Thus, aging may translate directly into reduced uptake at higher trophic levels. Nutrient additions in enclosures with benthivorous fish had a positive effect on PCB accumulation by these fish. Measured bioaccumulated concentrations of PCBs and PAHs in invertebrates in flood plain lakes were not influenced greatly by seasonal effects or ecological structure. Although effects were statistically significant, their magnitude in terms of accumulation factors was small, which may have been caused by the similar sediment composition and bioavailability of contaminants in our systems. Differences between compounds were much larger than differences due to ecosystem structure, seasons, or species composition. As for total masses of PCBs and PAHs in certain compartments however, lake ecosystem structure appeared to have a large influence on the biomass of biota and therefore also on the mass distribution of PCBs and PAHs in biotic compartments. Thus, changes in ecosystem structure strongly influenced PCB and PAH dynamics, although concentrations within the biotic compartments were not significantly influenced by biotic biomass. As for bioaccumulation modelling, when aquatic exposure concentrations were quantified accounting for sorption to carbonaceous materials, model results improved substantially. Including metabolic transformation and sediment uptake in the model accounted for a further improvement of the model fit. Implications are discussed for food chain bioaccumulation modeling, bioavailability assessment, sediment policy making and floodplain lake management.
Het voorkomen van loopkevers binnen een vegetatiegradiënt in de Millingerwaard (Coleoptera, Carabidae)
Verdonschot, R.C.M. ; Noordijk, J. ; Sykora, K.V. ; Schaffers, A.P. - \ 2007
Entomologische Berichten 67 (2007)3. - ISSN 0013-8827 - p. 82 - 91.
habitatselectie - multivariate analyse - stroomvlakten - vegetatie - coleoptera - insecten - gelderse poort - habitat selection - multivariate analysis - floodplains - vegetation - coleoptera - insects - gelderse poort
Op basis van een vangpotonderzoek wordt de relatie tussen het voorkomen van loopkeversoorten, abiotische factoren en de vegetatie beschreven. Het onderzoek werd uitgevoerd in 2004 in de Millingerwaard. Er kan geconcludeerd worden dat bepaalde loopkeversoorten alleen bij een bepaald type vegetatie voorkomt
Identifying the appropriate scales to model nitrogen flows from land to water
Dumont, E.L. - \ 2007
Wageningen University. Promotor(en): Rik Leemans; A. Stein, co-promotor(en): Carolien Kroeze; Lex Bouwman; Evert Jan Bakker. - [S.l.] : S.n. - ISBN 9789085046516 - 142
stikstof - stroming - modellen - land - water - stroomvlakten - rivieren - kustwateren - nitrogen - flow - models - land - water - floodplains - rivers - coastal water
Human activities cause flow of nitrogen (N) from terrestrial to aquatic systems. This has many serious consequences that need to be alleviated. Understanding and anticipation of N flow to aquatic systems can be achieved by modeling. Several models have been developed but one of their major weaknesses is the use of inappropriate scales. Therefore, the objective of this thesis is to increase our ability to identify appropriate spatial and temporal scales for N-flow models in a transparent and comprehensive way. In order to meet this objective, the following sub-objectives are addressed:
II. To develop aframeworkfor identifying the appropriate spatial and temporal scales of N-flow models.
III To apply this framework to a model of global N flow.
IV To assess the applicability of this framework to models of N flow between floodplains and rivers.First, a spatially explicit, global model for predicting dissolved inorganic nitrogen export (DIN) by rivers to coastal waters (NEWS-DIN) is developed. NEWS-DIN models DIN export from watersheds to coastal waters as a function of N inputs to watersheds including manure N, fertilizer N, atmospheric N deposition, and biological N 2 fixation, as well as sewage. NEWS-DIN also includes retention and loss terms, including N retention in river networks, N retention in dammed reservoirs, N loss via consumptive water use,denitrificationin rivers, and N loss via harvesting and grazing. For global watersheds DIN yields are calculated ranging from 0.0004 to 5217 kg N km -2 y -1 with the highest DIN yields occurring in Europe and
Avoidance of polycyclic aromatic hydrocarbon-contaminated sediments by the freshwater invertebrates Gammarus pulex and Asellus aquaticus
Lange, H.J. de; Sperber, V. ; Peeters, E.T.H.M. - \ 2006
Environmental Toxicology and Chemistry 25 (2006)2. - ISSN 0730-7268 - p. 452 - 457.
waterverontreiniging - sediment - stroomvlakten - besmetters - toxicologie - polycyclische koolwaterstoffen - waterinvertebraten - waterdieren - gammarus pulex - asellus aquaticus - waterbodems - ecotoxicologie - water pollution - sediment - floodplains - contaminants - toxicology - polycyclic hydrocarbons - aquatic invertebrates - aquatic animals - gammarus pulex - asellus aquaticus - water bottoms - ecotoxicology - oligochaete lumbriculus-variegatus - induced community tolerance - rhine-meuse delta - pollution - toxicity - amphipod - metals - food - earthworm - responses
Contamination of sediments is a serious problem in most industrialized areas. Sediments are often contaminated with trace metals and organic contaminants like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Bioassays are often used to determine the effect of contaminants on biota. However, survival or growth may not be the most sensitive endpoints. Behavioral changes often occur at much lower concentrations. Our study aimed to assess the effect of PAHs on habitat choice of two common freshwater invertebrates, the amphipod Gammarus pulex and the isopod Asellus aquaticus. We spiked clean field sediment with a mixture of four PAHs, fluoranthene, pyrene, chrysene, and benzo[k]fluoranthene, to a total concentration of 30 mg PAH/kg dry weight. Both species were offered a choice between PAH-spiked sediments and clean sediments in laboratory experiments. Results show that both species avoid PAH-spiked sediment. Origin of the population, either from a clean reference site or from a polluted site, did not affect habitat choice of either species
Trace metals in floodplain lake sediments : SEM/AVS as indicator of bioavailability and ecological effects
Griethuysen, C. van - \ 2006
Wageningen University. Promotor(en): Bart Koelmans. - [S.l. ] : S.n. - ISBN 9789085043652 - 223
sporenelementen - metalen - stroomvlakten - meren - sediment - verontreinigende stoffen - waterverontreiniging - methodologie - ecologie - risicoschatting - waterkwaliteit - nederland - land van maas en waal - trace elements - metals - floodplains - lakes - sediment - pollutants - water pollution - methodology - ecology - risk assessment - water quality - netherlands - land van maas en waal
This thesis addresses the geochemical aspects of AVS (Acid Volatile Sulfide) and SEM (Simultaneously Extracted Metals) in floodplain lake sediment, its spatial distribution in floodplain lakes and dynamics over time, the link with effects on single species (bioassays), as well as the impact of excess SEM on the in situ benthic community, in one consistent methodological approach. Using this approach the SEM-AVS concept is thus evaluated on various levels from geochemical through ecotoxicology towards ecology. Furthermore, the aspect of spatial and temporal variability is addressed. For the case studies in the field, several floodplain lakes located in the floodplain area Afferdensche and Deestsche Waarden along the Waal branche of the Rhine were selected. Occasionally, this selection was extended towards other floodplain lakes along the Rhine branches. The main goal of this research is a) to explore the actual risks of trace metals to benthic communities in floodplain systems and b) to evaluate the SEM-AVS concept as a tool to assess bioavailable concentrations of trace metals in dynamic floodplain sediment
Lilian van den Aarsen in de Havikerpoort; schakelen tussen de regio en de wereld van Den Haag
Hazeleger, B. ; Vos, C.C. - \ 2006
Landschap : tijdschrift voor landschapsecologie en milieukunde 23 (2006)2. - ISSN 0169-6300 - p. 70 - 74.
stroomvlakten - landschap - ecologische hoofdstructuur - veluwe - uiterwaarden - landscape - regional planning - ecological network - veluwe - river forelands
Op pad in haar favoriete landschap bij Middachten schetst Lilian van Aaarsen (LNV) met veel overtuiging hoe ze schakelend achtjes draait tussen de concrete inrichting in de regio en het Haagse Tweede-Kamer-Land. Het artikel bevat uitleg over de Havikerpoort: de ecologische verbinding tussen Veluwe en uiterwaarden van de IJssel
|Dynamiek versluiert; veldeffecten van metalen in dynamische ecosystemen
Klok, C. - \ 2006
Bodem 16 (2006)3. - ISSN 0925-1650 - p. 120 - 121.
ecosystemen - toxicologie - aardwormen - bodemfauna - overstromingen - stroomvlakten - zware metalen - ecotoxicologie - ecosystems - toxicology - earthworms - soil fauna - floods - floodplains - heavy metals - ecotoxicology
Deze bijdrage richt zich op de invloed van overstroming op de kans dat effecten van vervuiling zichtbaar worden op regenwormpopulaties
Effects of flooding on germination, establishment and survival of woody species; a field and modeling study on the floodplains of the river Rhine
Kramer, K. ; Nijhof, B.S.J. ; Vreugdenhil, S.J. ; Werf, D.C. van der; Wyngaert, I.J.J. van den; Armbruster, J. ; Späth, V. ; Siepmann-Schinker, D. - \ 2006
Wageningen : Alterra (Alterra-rapport 1345) - 72
inundatie - kieming - vestiging - overleving - oeverbossen - stroomvlakten - wateropslag - hoogwaterbeheersing - houtachtige planten - nederland - duitsland - bomen - rijn - flooding - germination - establishment - survival - riparian forests - floodplains - water storage - flood control - woody plants - netherlands - germany - trees - river rhine
Climate change results in higher water levels and therefore more frequent flooding and longer inundation of the floodplains of the river Rhine. Retention basins are installed in Germany and anticipated in the Netherlands to reduce peak flows and to prevent loss of property. In Germany, many of the retention basins are covered with forests that have experienced few floodings and that may be severely damaged by an extensive flood. In the Netherlands, the allocation of retention basins provides opportunities for new forest development. In both cases, knowledge is required on the effects of flooding on germination, establishment and survival of woody species to support the selection of retention basins. We analyzed the effects of flooding regimes on germination, establishment and survival of both saplings and adult trees, using analyzing available data; by collecting observational data; by performing field experiments; and by integrating this knowledge in a simulation model. We found clear differences between species in their response to flooding characteristics. The model is available for future studies on selection of retention basins
Ecoflood guidelines : how to use floodplains for flood risk reduction
Blackwell, M.S.A. ; Maltby, E. ; Gerritsen, A.L. ; Haasnoot, M. ; Hoffmann, C.C. ; Kotowski, W. ; Leenen, E.J.T.M. ; Okruszko, T. ; Penning, W.E. ; Piorkowski, H. ; Platteeuw, M. ; Querner, E.P. ; Siedlecki, T. ; Swart, E.O.A.M. de - \ 2005
[S.l.] : Ecoflood Project - 144
stroomvlakten - hoogwaterbeheersing - overstromingen - risicovermindering - richtlijnen (guidelines) - rivieren - europa - risicobeheersing - floodplains - flood control - floods - risk reduction - guidelines - rivers - europe - risk management
The main objective of these guidelines is to promote the use of floodplains as natural flood defence measures, while at the same time optimising other compatible functions and values through conservation and restoration. It is intended that these guidelines will be used as a tool primarily by policy-makers and decision-makers who are aware of the potential advantages of floodplain restoration and management in the role of flood control, but may benefit from comprehensive guidance on assessing, initiating, funding and carrying-out such schemes as well as information on the other functions floodplains can perform. It is also intended that they will be an accessible source of information for a wide range of stakeholders with an interest in floodplain management. Case studies are provided to illustrate the wide range of schemes that can be carried out and the degrees of success that have been achieved. Case studies from the Netherlands are: 1. Meinerswijk, Rhine; 2. Zandmaas and Grensmaas, Meuse; 3. Gamerensche Waard, Lower Rhine; 4. Afferdensche en Deestsche Waarden, Lower Rhine
|Rehabilitating large regulated rivers; lowland river rehabilitation conference; Wageningen, 29 september - 3 oktober 2003
Buijse, A.D. ; Klijn, F. ; Leuven, R.S.E.W. ; Middelkoop, H. ; Schiemer, F. ; Thorp, J.H. ; Wolfert, H.P. - \ 2005
Stuttgart (Germany) : Schweizerbart (Archiv für Hydrobiologie Suppl. vol. 155, no. 1-4) - 738
stroomvlakten - herstel - rivierregulering - rivieren - hydrobiologie - floodplains - rehabilitation - river regulation - rivers - hydrobiology
Regulating rivers has reduced the natural dynamic processes, altered the landscape and its biodiversity. Along large rivers that serve manifold functions, rehabilitation attempts have recovered stretches or certain features, but complete restoration probably will be a utopia. Key questions of the conference were e.g. how sustainable or effective are we so far; how well did we assess our achievements; what are the costs and benefits, opportunities and constraints, the end-points? More than 50 oral contributions and over 40 posters were presented at the conference, 45 of which, from 14 different countries, are published as peer-reviewed papers in this issue
Macrophyte succession in floodplain lakes : spatio-temporal patterns in relation to river hydrology, lake morphology and management
Geest, G.J. van - \ 2005
Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Rudi Roijackers; H. Coops. - s.l. : S.n. - ISBN 9789085041511 - 157
waterplanten - waterorganismen - stroomvlakten - hydrologie - plantensuccessie - vegetatie - patronen - waterstand - rijn - aquatic plants - aquatic organisms - floodplains - hydrology - plant succession - vegetation - patterns - water level - river rhine
Two questions are central to the work in this thesis: 1. What are the factors determining macrophyte composition in floodplain lakes along the Lower Rhine? 2. What advice can be given for design of future water bodies?
Decision Support System for Floodwater Spreading Site Selection in Iran
Kheirkhah Zarkesh, M. - \ 2005
Wageningen University. Promotor(en): Leo Stroosnijder, co-promotor(en): A.M.J. Meijerink; M.A. Sharifi. - Enschede : ITC - ISBN 9789085042563 - 259
hoogwaterbeheersing - inundatie - waterbeheer - besluitvorming - simulatiemodellen - iran - stroomvlakten - overstroomde gronden - beslissingsondersteunende systemen - flood control - flooding - water management - decision making - simulation models - iran - floodplains - flooded land - decision support systems
Keywords: DSS, remote sensing, GIS. spatial multi-criteria evaluation, analytical hierarchy process, floodwater spreading, groundwater recharge, Iran.
Most aquifers of semi-arid Iran suffer from over-exploitation of groundwater for irrigation. It is therefore important to augment the groundwater resource by artificial recharge, using flood waters that flow into salt lakes or in the sea. The recharge schemes consist generally of diversion of part of the flood discharges of ephemeral rivers in small to medium sized catchments onto infiltration basins.
Apart from recharge of groundwater, supporting food production and drinking water supplies, the schemes have other benefits, such as mitigation of flood damages and 'greening of the desert'. Many governments, including the one of Iran, place now much emphasis on increasing the number of floodwater spreading schemes.
A large number of factors play a role in the selection of the most suitable sites for deciding on investment in a scheme. These factors pertain to earth science (geology, geomorphology, soils), to hydrology (runoff and sediment yield, infi!tration and groundwater conditions) and to socio-economic aspects (irrigated agriculture, flood damage mitigation, environment, job creation and so on). Hence, the decision depends on criteria ofdiverse nature.
This thesis deals with developing a Decision Support System (DSS) to assist decisions as to where the most suitable catchments and associated infiltration areas are and to work out options of types of schemes, which are adjusted to the characteristics ofthe selected infiltration area (the site available).
After discussion of the bio-physical setting for flood spreading schemes in the Introduction (Chapter 1), attention is given to the selection ofthe desired approach for multi-criteria evaluation in Chapter 2. The Analytical Hierarchical Processes (AHP) approach was considered to be appropriate for the problem at hand and use was made of the spatial extension of this approach in a GIS environment, after structuring all the major criteria for a flood spreading scheme.
Of key importance is of course the expected infiltration of flood water diverted. For such an a-priori estimate the effect of soil textures in a soil column on infiltration and percolation have to be made, as well as an estimate of the effects of sedimentation of clay and sand in a scheme, as well as effect of inundation depth and flooding frequency. One-dimensional soil modelling was done with the SWAP model. Chapter 3, using two pedo-transfer functions for the hydraulic parameters based on textures. It was found that for coarse textured soils there was reasonable agreement between functions used, but quite some differences were found for the soils containing clay and silt. As expected, recharge efficiency was positively affected by inundation depth and by rapid succession of inundations.
Because simulation results differed, the recharge of the complex and large Sorkhehesar scheme was analysed, by developing a spreadsheet programme to work out depths, areas and duration of inundation. Chapter 4. It was found that the Mnalem-van Genuchten transfer function was the most appropriate one.
Given the large number of ephemeral rivers draining hilly catchments and passing through alluvial areas, is necessary to first use a rapid screening method to obtain zones which contain promising areas, for which the main criteria are applicable. The screening depends heavily on interpretation of remotely sensed images, which have the advantage that various aspects are presented in a synoptic view. The interpretation has to have a firm footing in earth science because runoff and sediment delivery processes have to be estimated in qualitative terms, as well as aquifer properties. A number of examples from Iran have been described in Chapter 5, highlighting the importance of transmission losses.
In order to select the most suitable area among the promising ones, the spatial AHP was applied in the Varamin zone under consideration of a multitude of criteria, in Chapter 6. The difficulty in the application was to develop and specify the preferences that are the base of the relative importance values for all the decision criteria involved at different levels, once the various factors had been estimated using standard hydrological and other methods. The use of the linguistic measures of preferences in the pair-wise comparisons made it possible to implement the full procedure, even though data differed much in nature, consistency and quality. In the Varamin zone, the Chandab catchment and infiltration area came out as the ''most satisfying" area; it had the highest sum of utilities for three of the four objectives and the highest score in a combination scenario.
For the Chandab infiltration site, a spreadsheet model was developed to work out various options with regard to type of scheme (shallow basin or deep basin type) and size of scheme, resulting in the expected volumes of recharge during the lifetime of the scheme by assuming desilting operations. Of the additional benefits, the flood damage mitigation could be expressed in monetary terms, and that benefit had a profound effect on the cost per unit volume of recharge water if one opts for the two large sized scheme designs.
To our knowledge, this study presents for the first time information on costs and benefits of a flood water spreading scheme in Iran in a structured manner of various designs adjusted to a particular site.
The final conclusion (Chapter 8) states that the DSS described here, with its three stages of increasing focus and associated data requirements and with the approach for evaluation using a multitude of criteria of diverse nature, has proven to be applicable and an efficient way to select the most appropriate alternatives for making a choice for investment in a flood spreading scheme. Although the emphasis was on Iranian conditions, the DSS is essentially of generic nature and may be applied ~ mutatis mutandis- to other semi arid regions.
Modeling of the solid-solution partitioning of heavy metals and arsenic in embanked flood plain soils of the rivers Rhine and Meuse
Schröder, T.J. ; Hiemstra, T. ; Vink, J.P.M. - \ 2005
Environmental Science and Technology 39 (2005)18. - ISSN 0013-936X - p. 7176 - 7184.
bodemverontreiniging - zware metalen - arsenicum - stroomvlakten - rivieren - geochemie - nederland - bodemkwaliteit - rijn - maas - soil pollution - heavy metals - arsenic - floodplains - rivers - geochemistry - netherlands - soil quality - river rhine - river meuse - ray-absorption spectroscopy - hydrous manganese oxide - natural organic-matter - goethite alpha-feooh - biotic ligand model - ion-binding - surface complexation - contaminated soils - pb(ii) sorption - acute toxicity
The aim of this study is to predict the solid-solution partitioning of heavy metals in river flood plain soils. We compared mechanistic geochemical modeling with a statistical approach. To characterize the heavy metal contamination of embanked river flood plain soils in The Netherlands, we collected 194 soil samples at 133 sites distributed in the Dutch part of the Rhine and Meuse river systems. We measured the total amounts of As, Cd, Cr, Cu, Ni, Pb, and Zn in the soil samples and the metal fraction extractable by 2.5 mM CaCl2. We found a strong correlation between heavy metal contamination and organic matter content, which was almost identical for both river systems. Speciation calculations by a fully parametrized model showed the strengths and weaknesses of the mechanistic approach. Cu and Cd concentrations were predicted within one log scale, whereas modeling of Zn and Pb needs adjustment of some model parameters. The statistical fitting approach produced better results but is limited with regard to the understanding it provides. The log RMSE for this approach varied between 0.2 and 0.32 for the different metals. The careful modeling of speciation and adsorption processes is a useful tool for the investigation and understanding of metal availability in river flood plain soils