Propagation of hydro-geomorphic disturbances through continental-scale river basins: Future evolution of the Amazon River and its floodplain

Hundreds of millions of people live close to, and depend upon, the world's large rivers for water, food, transport and the maintenance of a thriving ecosystem. However, these rivers are increasingly vulnerable to the effects of a wide range of natural and human-induced disturbances, including climate change, construction of large dams, river engineering works, deforestation, agricultural intensification, and mining activity. Over the past 20 years, climate change and deforestation have impacted on the hydrology and sediment fluxes within the Amazon River Basin. However, the Amazon has remained one of the few large river systems that has been largely unaffected by dams. This situation is changing rapidly, because widespread hydropower dam construction in Brazil, Bolivia, Peru and Ecuador now threatens the basin, with >300 dams planned or under construction. These dams are expected to trigger severe hydro-physical and ecological disturbances throughout the basin, including massive reductions in sediment and nutrient delivery to the lowland Amazon and its floodplains, substantial degradation of river beds and banks, significant changes in river water levels and flooding, and adverse impacts on river and floodplain ecosystems, on which the human population depends.

Recent high profile studies highlight the need for international action to assess and mitigate these impacts, both in the Amazon and elsewhere. However, our capacity to do this is severely restricted by an absence of quantitative models that can predict how environmental disturbances propagate through large rivers and floodplains, over continental distances, and decadal to centennial time periods. Critically, environmental disturbances driven by dams, climate and land cover change promote dynamic river responses (e.g., changes in river width, depth, slope, sediment size, degree of branching and rate of floodplain reworking), which in turn control changes in flood conveyance and downstream sediment delivery. Despite advances in modelling of river dynamics over short distances (<100 km), hydrological models that are applied to continental-scale drainage basins treat rivers and floodplains as static conduits. Consequently, such models are unable to represent or predict the future impacts of environmental change on flooding, sediment fluxes or river and floodplain functioning.

This project will deliver a step-change in our ability to model, predict and understand how the world's large rivers are impacted by, and respond to, environmental change. We will achieve this by implementing a research strategy that involves six elements: First, we will develop a new multi-scale numerical modelling approach that enables the effects of river dynamics on environmental disturbance propagation through continental-scale drainage basins to be simulated. Second, we will develop a suite of environmental scenarios representing climate and land cover changes and dam construction throughout the Amazon Basin for the recent past (1985-2015) and future (up to 2200). Third, we will collect new field datasets at sites on the Amazon River that are required to test key components of the model. Fourth, we will work with an international team of project partners to assemble high-resolution field, satellite and model datasets that quantify channel and floodplain processes, and river morphology and dynamics throughout the Amazon Basin. Fifth, we will use these data to carry out rigorous testing of our new model. Sixth, we will apply the model to predict the future evolution of the Amazon River and its tributaries for a wide range of environmental change scenarios, and quantify the controls on hydro-geomorphic disturbance propagation within large drainage basins. We will work with our project partners to disseminate our model code, datasets and project outcomes to non-academic stakeholders, both nationally and internationally.

The scientific advances that will be delivered by this project have direct relevance to a wide range of agencies concerned with economic, social, management and policy issues. Key beneficiaries of this research will include:

1. National and international engineering organisations and environmental consultancies that use numerical models to assess flood risk, infrastructure stability, sediment management problems, or aquatic habitat suitability.

2. Government agencies with responsibility for river management and policy planning in the context of flood mitigation, disruption to bankside communities and infrastructure, navigation, sediment management, and future climate change. Potential benefits of our research to these agencies are diverse, and include an ability to understand and quantify the impacts on riparian and floodplain communities of policy decisions related to dam construction, land cover change, flow regulation, and river engineering works.

3. International, national and regional NGOs that work to support local communities and seek to: (a) understand the potential environmental, social and economic impacts in river and floodplain landscapes resulting from the effects of climate change and anthropogenic activity; (b) support local communities affected by these impacts; (c) raise public awareness of impacts and their causes; and (d) influence and inform government policy designed to adapt to, and mitigate, these impacts.

4. GCSE and A Level geography teachers and students who study flood processes and flood vulnerable environments as part of the curricula and have to demonstrate quantitative data skills as part of their fieldwork and formative assessment.

These groups will benefit from the research undertaken here in multiple ways:

1. The numerical models developed in this project will be directly applicable to the river management problems addressed by these beneficiaries. Our models (and open source code) will be freely available to these agencies. We will also deliver workshop activities in the UK and USA to support training in the use of our models and their uptake by a broad group of beneficiaries.

2. To deliver benefits to these groups rapidly, we will work with two such agencies (the US Army Corps of Civil Engineers and their partners the Brazilian National Department of Transportation Infrastructure) to facilitate their use of our models and model datasets. This will include the co-design of our model simulations to address questions of specific concern to these Agencies on the Madeira River in Brazil, and support to enable the application of our models in other river basins of particular interest to these groups.

3. To maximise the longer-term benefits of our research we will disseminate our project outcomes in policy relevant formats to NGOs and government agencies with interests throughout the Amazon Basin. We will also run a widely publicised forum event, hosted by our partner the Royal Geographical Society, to debate the outcomes of our work with national and international engineering and environmental consulting companies, charities, government advisors and environmental lobbyists.

4. To deliver benefits from our research to teachers and students we will work with the RGS to produce educational resources targeted at GCSE and A level students, and undertake educational outreach activities at national events.