Floodplain Management Research Articles

Surviving Invasion: Regaining Native Fish Resilience Following Fish Invasions in a Modified Floodplain Landscape

AbstractFloodplain ecosystems are focal points for human settlement, and consequently are often subjected to extensive modification and infrastructure development. Establishment of non‐native species in floodscapes presents a range of challenges when they become problematic and drive changes in native aquatic communities and ecosystems. These non‐native species are often tolerant of reduced water and habitat quality, conferring a competitive advantage over native species. The coupled effects of invasive alien species, landscape modification and floodscape hydrological control collectively reduce ecological resilience, creating feedback loops that reinforce negative effects on native fish. The regulated lower Waikato River floodplain is a New Zealand hotspot for fish introductions, with their proliferation exacerbating the effects of agricultural development, urban expansion, and flood control infrastructure. We argue that the resilience of native fish assemblages to these pressures can be improved through utilizing a series of complementary measures, including enhanced catchment management, strategic alterations to the location, design, and operation of floodplain infrastructure (e.g., gates, pumpstations, and stopbanks), habitat restoration for native fish, and targeted management of invasive species. These measures will need to consider the likely persistence of invasive alien fish, however, to limit their expansion in the face of a changing climate. Although knowledge and implementation gaps exist, tying these strands together presents an opportunity to enhance the resilience of native fisheries into the future. Key to success will be re‐thinking floodplain management to include ecosystem services, and this will require ongoing commitment and cooperation amongst all stakeholders to address knowledge gaps and enable effective implementation.

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 Lasting Legacy of Hazard and Choice Perception in Flood Plain Management by Robert Kates

This Classics Revisited/From the Archives paper summarizes the 1962 publication of Robert Kates regarding perceptions of the flooding hazard in LaFollette, Tennessee, and five other cities that were used for comparison. The influence of this work on improvements in flood hazards since 1962 are discussed, as well as suggestions as to how this work will continue to influence flood hazard management and mitigation.

Identifying tree characteristics to determine the blocking effects of water conveyance for natural flood management in urban rivers

AbstractPlants, especially trees, provide ecological functions but may harm the flood conveyance efficiency of rivers. Understanding the impacts of tree heights, tree areas, and tree locations on flood levels is crucial for floodplain management. This study aims to present a methodology to improve the performance of hydrodynamic modeling by considering plant resistance with the goal of analyzing flood risk reduction strategies that support ecological conservation enhancement. An unmanned aerial vehicle was used to collect floodplain topography, landcover, and tree characteristic data. A modified maximum likelihood classification scheme was developed by incorporating the tree height information to improve the landcover classification. The water‐blocking effect of trees, which represents the reduced flood conveyance area, was investigated by establishing tree obstructions in hydrodynamic models. Two hydrodynamic models were established with different tree obstruction setups and Manning's n values, including blocked obstructions (BOs) and conventional high n‐values (Adj‐n). Among the model setups, the Manning's n values of the trees remained the same as that of the soil in the BO model, in which trees were modeled as blocking obstructions. The n‐values of trees were determined to be 0.022 in the BO model and refined to 0.055 in the Adj‐n model after the model calibration and verification processes. The results indicated that the simulated flood levels of the BO model were very similar to those of the Adj‐n model. The NSE values were 0.98 and 0.97 in the simulations of two historical typhoon events, indicating that the BO model could obtain reliable predictions without altering the n‐values. The verified BO model was used to evaluate the degrees of influence of tree heights, tree coverage areas, and tree locations on flood levels. Several nature‐based solutions were proposed to analyze the tradeoffs between reducing flood prevention and enhancing wetland restoration using the verified BO model, suggesting a win–win strategy for natural river management.

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.

Establishing a framework of a watershed-wide screening tool to support the development of watershed-based flood protection plans for low-lying coastal communities

Flood risk analysis is the instrument by which floodplain and stormwater utility managers create strategic adaptation plans to reduce the likelihood of flood damages in their communities, but there is a need to develop a screening tool to analyze watersheds and identify areas that should be targeted and prioritized for mitigation measures. The authors developed a screening tool that combines readily available data on topography, groundwater, surface water, tidal information for coastal communities, soils, land use, and precipitation data. Using the outputs of the screening tool for various design storms, a means to identify and prioritize improvements to be funded with scarce capital funds was developed, which combines the likelihood of flooding from the screening tool with a consequence of flooding assessment based on land use and parcel size. This framework appears to be viable across cities that may be inundated with water due to sea-level rise, rainfall, runoff upstream, and other natural events. The framework was applied to two communities using the 1-day 100-year storm event: one in southeast Broward County with an existing capital plan and one inland community with no capital plan.

Evaluating and tracking investments in natural infrastructure to reduce coastal flooding hazards

ABSTRACT Protection and restoration of natural infrastructure are fairly new tactics to reduce coastal flood hazards. Increasingly, floodplain managers and environmental organizations have advanced use of these solutions and communities have embraced them, owing to the perceived multiple benefits derived from these projects. Assessing progress in the use of natural infrastructure solutions requires means to account for projects. One way to measure progress is to track investments made in such projects. This paper analyzes and estimates the United States’ investments in natural infrastructure and provides a replicable method for determining whether a project qualifies as an investment in natural infrastructure that could reduce flood hazard and, therefore, have a coastal risk reduction benefit. Estimates of annual investment between 2012 and 2018 indicate increasing, yet variable, annual investment. Better data availability would improve the accuracy of findings.

Assessing climate-change-induced flood risk in the Conasauga River watershed: an application of ensemble hydrodynamic inundation modeling

Abstract. This study evaluates the impact of potential future climate change on flood regimes, floodplain protection, and electricity infrastructures across the Conasauga River watershed in the southeastern United States through ensemble hydrodynamic inundation modeling. The ensemble streamflow scenarios were simulated by the Distributed Hydrology Soil Vegetation Model (DHSVM) driven by (1) 1981–2012 Daymet meteorological observations and (2) 11 sets of downscaled global climate models (GCMs) during the 1966–2005 historical and 2011–2050 future periods. Surface inundation was simulated using a GPU-accelerated Two-dimensional Runoff Inundation Toolkit for Operational Needs (TRITON) hydrodynamic model. A total of 9 out of the 11 GCMs exhibit an increase in the mean ensemble flood inundation areas. Moreover, at the 1 % annual exceedance probability level, the flood inundation frequency curves indicate a ∼ 16 km2 increase in floodplain area. The assessment also shows that even after flood-proofing, four of the substations could still be affected in the projected future period. The increase in floodplain area and substation vulnerability highlights the need to account for climate change in floodplain management. Overall, this study provides a proof-of-concept demonstration of how the computationally intensive hydrodynamic inundation modeling can be used to enhance flood frequency maps and vulnerability assessment under the changing climatic conditions.

Flood hazard areas assessment at a regional scale in M'zi wadi basin, Algeria

Located in the semi-arid areas of Algeria, M'zi wadi basin experienced severe floods that pose a potent threat to the present day. In order to reduce and mitigate flood damage there is a need to develop tools for effective flood hazard management at basin scale, the paper aims to mapping of flood hazard potential areas in M'zi wadi basin, using Analytic Hierarchy Process (AHP) approach coupled with Geographic Information System (GIS), based on several parameters that are relevant to flood hazard which has been weighted depending to their contributions. The Rainfall-Runoff-Inundation (RRI) model was also used in this study to understanding the hydrological behavior of M'zi wadi basin and to evaluate the efficiency of structural measures in downstream areas of basin.The results show a reasonable agreement with the inundated areas detected by Sentinel-2 imagery. The result of the flooding hazard in M'zi wadi basin reveals that 3%, 0.84%, 67%, 29%, and 0.16% of the catchment is high, very high, moderate, low, and very low flooding hazard areas respectively. The results show also that urban areas and agricultural areas surrounding of the lower portion of M'zi wadi are extremely exposed to flooding. The RRI model simulation results shows that the new dam -under construction-can reduce the magnitude of peak storm runoff only by 7%, and the widening of wadi near to outlet of basin can help to reduce the water level at this segment by 22% compared with results of simulation of naturalized conditions.Flood hazard areas assessment at M'zi wadi basin level can be used by concerned government's department as an excellent supporter of decision-makers during extreme and intense rainfall events in making floodplain management decisions.

Effects of plant species identity override diversity effects in explaining sedimentation within vegetation in a flume experiment

AbstractDuring floods, sediments suspended in river water deposit on floodplains. Thus, floodplains are a key to improving river water quality. Yet, the factors that determine the amount of fine sediment that deposits on floodplains are largely unknown. Plant diversity typically increases structural diversity, whereas the vegetation structure and the structural characteristics of individual species are known to influence sedimentation. We hypothesised that species diversity, in addition to species identity, may promote sediment retention. Our study aimed to disentangle the effects of species richness and species identity, via differences in vegetation structure, on sediment retention within herbaceous vegetation patches. In a flume experiment, we investigated sedimentation on 30 vegetation patches (40 × 60 cm2). We created patches with five different species‐richness levels (3, 4, 6, 8, and 11 species), each replicated six times. Species were randomly selected from 14 common floodplain species. We inundated the patches with silt‐ and clay‐rich water and measured the amount of accumulated sediment on the vegetation and on the ground underneath it. Species richness significantly increased sedimentation underneath the vegetation (R2 = 0.17). However, including species identity effects in a structural equation model, we showed that individual species' presence largely drove these effects. Alopecurus pratensis had a direct negative effect on sedimentation on the vegetation, whereas Bromus inermis and Elymus repens had indirect positive effects through an increase in total biomass (R2 = 0.42). Elymus repens had a direct negative, and Urtica dioica a direct positive effect on sedimentation underneath the vegetation (R2 = 0.38). Our results indicate that selecting the most effective species, rather than as many species as possible, may have the greatest benefits for promoting sedimentation. Overall, we conclude that floodplain management that aims to increase sediment retention should alter the vegetation structure of meadows by increasing vegetation biomass.

Assessing Spatial Variation in Algal Productivity in a Tropical River Floodplain Using Satellite Remote Sensing

Studies of tropical floodplains have shown that algae are the primary source material for higher consumers in freshwater aquatic habitats. Thus, methods that can predict the spatial variation of algal productivity provide an important input to better inform management and conservation of floodplains. In this study, a prediction of the spatial variability in algal productivity was made for the Mitchell River floodplain in northern Australia. The spatial variation of aquatic habitat types and turbidity were estimated using satellite remote sensing and then combined with statistical modelling to map the spatial variation in algal primary productivity. Open water and submerged plants habitats, covering 79% of the freshwater flooded floodplain extent, had higher rates of algal production compared to the 21% cover of emergent and floating aquatic plant habitats. Across the floodplain, the predicted average algal productivity was 150.9 ± 95.47 SD mg C m−2 d−1 and the total daily algal production was estimated to be 85.02 ± 0.07 SD ton C. This study provides a spatially explicit representation of habitat types, turbidity, and algal productivity on a tropical floodplain and presents an approach to map ‘hotspots’ of algal production and provide key insights into the functioning of complex floodplain–river ecosystems. As this approach uses satellite remotely sensed data, it can be applied in different floodplains worldwide to identify areas of high ecological value that may be sensitive to development and be used by decision makers and river managers to protect these important ecological assets.

Historical dredge mining as a significant anthropomorphic agent in river systems: A case study from south-eastern Australia

Bucket dredging to mine and extract gold and tin from rivers is a global industry that has had a range of negative effects on physical environments. These include the destruction of riparian soil profiles and structures, artificial channel straightening and loss of in-stream biodiversity. In this paper we evaluate the immediate effects and long-term consequences of bucket dredging on rivers in Victoria and New South Wales during the period 1900–1950. High quality historical sources on dredge mining are integrated with geospatial datasets, aerial imagery and geomorphological data to analyse the scale of the dredging industry, evidence for disturbance to river channels and floodplains and current land use in dredged areas. The study demonstrates that the environmental impact of dredging was altered but not reduced by anti-pollution regulations intended to control dredging. An assessment of river condition 70–100 years after dredge mining ceased indicates that floodplains and river channels continue to show the effects of dredging, including bank erosion, sediment slugs, compromised habitat and reduced agricultural productivity. These findings have significant implications for river and floodplain management.

Impact of linear transport infrastructure on fluvial connectivity across the catchments of West Bengal, India

Floodplain corridors contain ∼21% of the total land area of West Bengal and hold alignment of ∼44% road and ∼26% railway networks of the state. Therefore, understanding of potential interactions between transport infrastructure and river systems is essential for river basin management in general and understanding the longitudinal and lateral (dis)connectivity across the twenty catchments of WB in particular. Freely available GIS data has been used for future river and floodplain management and policy making using multiple spatial analytical tools. The study finds ∼21% of the floodplain area is laterally disconnected from rivers, which could be raised by 260% after considering riverside artificial embankment. About 40% of state’s land area comes within one kilometre proximal distance between river and transport networks and ∼13% of transport networks are at risk of waterlogged during a flood. This study has recommended a river friendly comprehensive plan for transport network development in the future.

Plant structural diversity alters sediment retention on and underneath herbaceous vegetation in a flume experiment.

Sediment retention is a key ecosystem function provided by floodplains to filter sediments and nutrients from the river water during floods. Floodplain vegetation is an important driver of fine sediment retention. We aim to understand which structural properties of the vegetation are most important for capturing sediments. In a hydraulic flume experiment, we investigated this by disentangling sedimentation on and underneath 96 vegetation patches (40 cm x 60 cm). We planted two grass and two herb species in each patch and conducted a full-factorial manipulation of 1) vegetation density, 2) vegetation height, 3) structural diversity (small-tall vs tall-tall species combinations) and 4) leaf pubescence (based on trait information). We inundated the vegetation patches for 21 h in a flume with silt- and clay-rich water and subsequently measured the amount of accumulated sediment on the vegetation and on a fleece as ground underneath it. We quantified the sediment by washing it off the biomass and off the fleece, drying the sediment and weighting it. Our results showed that all manipulated vegetation properties combined (vegetation density and height, and the interaction of structural diversity and leaf pubescence) explained sedimentation on the vegetation (total R2 = 0.34). The sedimentation underneath the vegetation was explained by the structural diversity and the leaf pubescence (total R2 = 0.11). We further found that vegetation biomass positively affected the sedimentation on and underneath the vegetation. These findings are crucial for floodplain management strategies with the aim to increase sediment retention. Based on our findings, we can identify management strategies and target plant communities that are able to maximize a floodplain's ability to capture sediments.

Regional Scale Risk to the Ecological Sustainability and Ecosystem Services of an African Floodplain System.

The Phongolo floodplain is one of southern Africa's most important systems. In this study, we carried out a regional scale ecological risk assessment to evaluate the risk of multiple stressors associated with the use of the aquatic resources in the floodplain to selected social and ecological endpoints representing its sustainability. The floodplain has undergone significant changes as a result of the impacts of multiple stressors. This includes high risk of impact and threatened sustainability between the Pongolapoort Dam and the Ndumo Game Reserve (NGR). This compares to relatively low risk to the maintenance of the endpoints within the NGR. The reserve provides a protection and refuge function for regional biodiversity maintenance and ecosystem sustainability processes. In the study a range of scenarios were considered and demonstrate that the system will respond to protection measures and or increased resource use options. Should flood reductions or water quality pollution drivers continue on increasing trajectories, the condition of the Phongolo River and floodplain will probably deteriorate into an unacceptable, unsustainable state. Removal of the protection services of the NGR would result in an unsustainable ecosystem and loss of ecosystem services for regional vulnerable African communities. Additional evidence should be obtained from monitoring and research to refine, validate, and update the assessment in an adaptive management context. The risk assessment framework approach implemented in the Phongolo floodplain can contribute to the management of other floodplains ecosystems and the sustainability management of social and ecological attributes and processes of these important ecosystems.

A Review of Coupled Hydrologic-Hydraulic Models for Floodplain Assessments in Africa: Opportunities and Challenges for Floodplain Wetland Management

Floodplain wetlands are a fundamental part of the African continent’s ecosystem and serve as habitat for fish and wildlife species, biodiversity, and micro-organisms that support life. It is generally recognised that wetlands are and remain fragile ecosystems that should be subject to sustainable conservation and management through the use of sustainable tools. In this paper, we propose a synthesis of the state of art concerning coupled hydrologic and hydraulic models for floodplains assessments in Africa. Case studies reviewed in this paper have pointed out the potential of applying coupled hydrologic and hydraulic models and the opportunities present to be used in Africa especially for data scarce and large basin for floodplain assessments through the use of available open access models, coupling frameworks and remotely sensed datasets. To our knowledge this is the first case study review of this kind on this topic. A Hydrological model coupled with Hydraulic Model of the floodplain provides improvements in floodplain model simulations and hence better information for floodplain management. Consequently, this would lead to improved decision-making and planning of adaption and mitigation measures for sound floodplain wetland management plans and programmes especially with the advent of climate change and variability.

Soil Protection in Floodplains—A Review

Soils in floodplains and riparian zones provide important ecosystem functions and services. These ecosystems belong to the most threatened ecosystems worldwide. Therefore, the management of floodplains has changed from river control to the restoration of rivers and floodplains. However, restoration activities can also negatively impact soils in these areas. Thus, a detailed knowledge of the soils is needed to prevent detrimental soil changes. The aim of this review is therefore to assess the kind and extent of soil information used in research on floodplains and riparian zones. This article is based on a quantitative literature search. Soil information of 100 research articles was collected. Soil properties were divided into physical, chemical, biological, and detailed soil classification. Some kind of soil information like classification is used in 97 articles, but often there is no complete description of the soils and only single parameters are described. Physical soil properties are mentioned in 76 articles, chemical soil properties in 56 articles, biological soil properties in 21 articles, and a detailed soil classification is provided in 32 articles. It is recommended to integrate at least a minimum data set on soil information in all research conducted in floodplains and riparian zones. This minimum data set comprises soil types, coarse fragments, texture and structure of the soil, bulk density, pH, soil organic matter, water content, rooting depth, and calcium carbonate content. Additionally, the nutrient and/or pollution status might be a useful parameter.

A multiple‐lines‐of‐evidence approach for prioritising environmental watering of wetland and floodplain trees

AbstractLong‐lived vegetation is a key attribute of lowland river floodplains; yet dieback is increasingly being reported globally, with prior studies identifying salinity, drought and altered flow regimes as key stressors. In the Murray–Darling Basin (Australia), many floodplain/wetland areas have management strategies that aim to maintain the condition of floodplain tree communities. Environmental water delivery is a key tool used to achieve such outcomes. Currently, one of the primary tools for determining the need for environmental water delivery is a qualitative visual assessment of tree crown condition. To advance to more quantitative assessment and understanding of tree condition, we present a suite of techniques ranging from low‐cost, rapid visual assessment of tree crown condition to laboratory analysis of components of soil condition and in situ measurement of tree physiology. The aim is to address a number of key knowledge gaps on how to use the linkages between soil water availability ↔ tree physiology ↔ tree visual condition to quantitatively inform environmental water delivery decisions to meet management objectives. We have developed a multiple‐lines‐of‐evidence management assessment framework that presents a pathway to enable managers to improve prioritisation management actions. Furthermore, increased confidence in predicted outcomes should assist water holders and floodplain managers to optimise timing and maximise the benefits of environmental watering. Application of outcomes of this research will increase the efficiency of environmental water use.

Prediction modelling of riverine landscape dynamics in the context of sustainable management of floodplain: a Geospatial approach

ABSTRACT Presently, sustainability of floodplain, a diverse element of the riverine landscape, provides an ideal research setting for investigating complex interaction between anthropogenic disturbance and eco-environmental degradation. Nowadays, these floodplains are continually degraded and fragmented on account of unsustainable land use. To analyse the spatial and temporal changes of landuse/landcover, a supervised classification (maximum likelihood algorithm) method has been made for the period 1998 to 2018. Present research simulates and predicts landuse/landcover dynamics of lower stretch of the Ganges river up to 2038 to analyse future riverine landscape dynamics stressed by various natural and socio-economic factors based on Cellular Automata-Artificial Neuron Network (CA-ANN) model clubbed with Modules for Land Use Change Evaluation (MOLUSCE) plugin of QGIS software. Outcome of research reveals that the trend of agriculture land, sand, and inland waterbody areas is reduced by 15.75, 5.71, and 1.95%, whereas, for orchard, agricultural fallow and bare land areas increased by 7.94, 7.92, and 5.69% for the period from 1998 to 2018. The simulation model predicted a continuation of the similar trend till 2038. The significant reduction of agricultural land and sand areas is largely an attribute to floodplain degradation in an altered hydrological regime. Ultimately, hydro-morphological changes, increasing population pressure, and agriculture intensification in floodplain landscape were identified as main driving forces in temporal landuse/landcover changes. The prediction of future forecast indicates that if the present rate of landuse/landcover trend persists in the study stretch of Ganges river without appropriate sustainable development practice, severe floodplain degradation will ensue. This study provides a holistic measure for understanding long-term environmental degradation related to anthropogenic activities and impact of climate changes in floodplain landscape at local and regional scale.

Sustainable Floodplains: Linking E-Flows to Floodplain Management, Ecosystems, and Livelihoods in the Sahel of North Africa

Floodplains are particularly important in the semi-arid region of the Sub-Sahelian Africa. In this region, water governance is still being developed, often without adequate information and technical capacity for good, sustainable water resource management. However, water resources are being allocated for use with minimal sustainability considerations. Environmental flows (e-flows) include the quantity and timing of flows or water levels needed to meet the sustainable requirements of freshwater and estuarine ecosystems. Holistic regional scale e-flows linked to floodplain management can make a noticeable contribution to sustainable floodplain management. The Inner Niger Delta (IND) in Mali is an example of a vulnerable, socio-ecologically important floodplain in the Sahel region of North Africa that is being developed with little understanding of sustainability requirements. Although integrally linked to the Upper Niger River catchment, the IND sustains a million and half people within the region and exports food to surrounding areas. The flooding of the Delta is the engine of the socio-economic development as well as its ecological integrity. This paper aims to demonstrate the contribution that holistic regional e-flow assessment using the PROBFLO approach has to achieving floodplain sustainability. This can be achieved through the determining the e-flow requirements to maintain critical requirements of the ecosystems and associated services used by local vulnerable human communities for subsistence and describing the socio-ecological consequences of altered flows. These outcomes can contribute to the management of the IND. In this study, the socio-ecological consequences of altered flows have been evaluated by assessing the risk of alterations in the volume, duration, and timing of flows, to a number of ecological and social endpoints. Based on the risk posed to these endpoints by each scenario of change, an e-flow of 58% (26,685 million cubic meters (MCM) of water annually) was determined that would protect the ecosystem and maintain indicator components at a sustainable level. These e-flows also provide sustainable services to local communities including products for subsistence and limit any abnormal increases in diseases to the vulnerable African communities who live in the basin. Relative risk outputs for the development scenarios result in low-to-high-risk probabilities for most endpoints. The future development scenarios include insufficient flows to maintain sustainability during dry or low-flow periods with an increase in zero flow possibilities. Although unsuitable during the low-flow or dry periods, sufficient water is available through storage in the basin to meet the e-flows if these scenarios were considered for implementation. The IND is more vulnerable to changes in flows compared to the rivers upstream of the IND. The e-flow outcomes and consequences of altered flow scenarios has contributed to the management of vulnerable IND floodplains and the requirements and trade-off considerations to achieve sustainability.