Assessing Feedback Responses of soil Erosion through the lens of variable Sediment connectivity during Extreme EveNts in semi-arid catchments.

Project Information

AsFoRESEEN

Grant agreement ID: 101109315

DOI

10.3030/101109315

EC signature date 13 July 2023

Start date 1 January 2024

End date 31 March 2027

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 288 737,28

Coordinated by

UNIVERSITEIT GENT
Belgium

Periodic Reporting for period 1 - AsFoRESEEN (Assessing Feedback Responses of soil Erosion through the lens of variable Sediment connectivity during Extreme EveNts in semi-arid catchments.)

Reporting period: 2024-01-01 to 2026-03-31

Summary of the context and overall objectives of the project

Soil resources in semi-arid regions are rapidly degrading, posing an imminent threat to food, water and livelihood security. Caveats in our understanding of geomorphological responses to extreme events are a major hindrance for attributing soil erosion and sediment flux dynamics to environmental drivers. Using the Burdekin and Makuyuni catchments as natural laboratories for semi-arid regions, the AsFoRESEEN project will assess feedback dynamics in soil erosion through the lens of variable sediment connectivity to test the hypothesis that extreme events can trigger regime shifts towards highly connected ephemeral gully networks. The proposed knowledge transfer strategies will bring the researcher’s scientific and analytical skills to the international standard, underpinning his ambition to combine academic and consultancy work within a leading European research institution. The researcher's unique skillset will be applied to develop novel approaches and integrate them with established techniques in an open-access diagnostic toolkit to support targeted soil- and water management interventions. Temporal dynamics in fine sediment and Phosphorous transport will be quantified using high-frequency sensors and sediment dating techniques. We will be the first to evaluate the use of secondary weathered metal species as tracers, providing a new pathway for attributing the contribution of gully erosion in deeply weathered or alluvials soils. Stream monitoring and sediment source tracing outputs will be integrated in a dynamic sediment budget to elucidate non-linear geomorphological responses to extreme events and land use changes. As a source of innovation, we will couple a machine-learning gully quantification tool with a dynamic catchment model, wherein gullies are both a direct source of sediment and a driver of changing sediment connectivity. The hybrid model will be used to test the efficacy of gully remediation strategies under current and future climatic conditions.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the reporting period, the project successfully executed its core technical programme, delivering major empirical datasets, analytical advances, and modelling frameworks underpinning Objectives O1–O3. Extensive field campaigns in Australia and Tanzania established high‑resolution hydrological and sediment monitoring networks, providing the empirical foundation for sediment‐budget development, tracer analysis, and model construction.
Objective O1 – Quantifying temporal dynamics of fine sediment and phosphorus transport is largely achieved. More than two years of near‑continuous measurements of discharge, suspended sediment concentration, particle size, and phosphorus dynamics were collected across gully, riverine, and catchment outlets. These high‑frequency datasets enabled reconstruction of storm‑event sediment behaviour, hysteresis patterns, seasonal dynamics, and long‑term sediment fluxes. Integration into catchment‑scale sediment budgets (Bonnie Doon and Albert River) revealed pronounced nonlinear sediment responses during extreme events, early evidence of geomorphic regime shifts, and strong linkages between hydrology, sediment connectivity, and catchment condition. Remaining work focuses on final budget synthesis and publication.
Objective O2 – Determining dominant sediment sources and erosion processes is also largely achieved. Extensive laboratory analyses, including sequential extractions, ICP‑MS, CSSIA, and synchrotron spectroscopy (MEXAS), produced a novel tracer suite capable of discriminating between surface soils, subsurface sources, alluvial banks, gullies, and distal hillslopes in deeply weathered tropical soils. These tracers were validated using artificial mixtures and applied to both integrated sediment budgets and event‑scale samples. Results demonstrate shifting sediment sources and strong source hysteresis during extreme floods, with alluvial and gully erosion dominating sediment supply in tropical savannah catchments. Tracer datasets are now fully integrated with sediment budgets, with multiple manuscripts in advanced preparation.
Objective O3 – Modelling remediation efficacy under future climatic conditions has been successfully initiated. A novel SWAT+Gully modelling architecture, adapted from the OPTAIN workflow, was designed to explicitly represent gullies as functional hydrological response units with dynamic sediment routing and connectivity. Historic and contemporary gully datasets, geospatial inputs, hydrological time series, and tracer‑derived source data have been compiled and prepared for calibration and scenario analysis. While process implementation and calibration are scheduled for the next phase, the modelling framework and data foundations are firmly established.
Across work packages, the project delivered: (i) fully operational monitoring networks in Australia and Tanzania; (ii) high‑quality, high‑frequency sediment and hydrological datasets; (iii) validated novel sediment tracers; (iv) near‑complete sediment budgets; and (v) a new, connectivity‑explicit modelling framework. Collectively, these outputs represent substantial technical progress toward all scientific objectives and provide a robust platform for final synthesis, modelling, and publication in the concluding project phase.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project has delivered several results that go substantively beyond the current state of the art in sediment dynamics, erosion science, and catchment modelling, particularly for tropical savannah and climate‑sensitive landscapes. Advances were achieved at methodological, empirical, and conceptual levels, generating results with clear potential for wider scientific and applied uptake.
A major advance lies in the generation and integration of high‑frequency, multi‑scale sediment datasets across gully, riverine, and catchment outlets. While high‑resolution monitoring has been advocated in theory, it is rarely sustained across multiple years and landscape units. This project provides one of the few empirical demonstrations of how storm‑scale sediment hysteresis, nonlinear connectivity, and threshold responses to extreme rainfall can be resolved in deeply weathered savannah catchments. These data reveal sediment transport behaviour that is not captured by traditional rating‑curve or annualised approaches, challenging prevailing assumptions of time‑invariant source contributions.
The project also advances sediment fingerprinting beyond existing tracer approaches. The development and application of secondary weathering species as novel tracers, validated through artificial mixtures, synchrotron spectroscopy, and field deployment, fills a long‑standing methodological gap in distinguishing subsurface, alluvial, and gully erosion in heavily weathered soils. This represents a step change over conventional geochemical and fallout radionuclide tracers, which often fail in tropical environments. The demonstrated ability to track rapid source switching during extreme events significantly extends the explanatory power of sediment tracing methods.
At the modelling frontier, the project delivers a new SWAT+Gully framework that explicitly represents permanent and ephemeral gullies as functional hydrological response units with dynamic routing and connectivity. Existing catchment models either omit gullies or treat them implicitly, limiting predictive skill under changing climate extremes. By integrating tracer‑derived source information, high‑frequency observations, and gully‑specific process conceptualisation, the framework enables scenario testing of remediation measures under both current and future climates, moving beyond static erosion representations.
Additional beyond‑state‑of‑the‑art contributions include a near‑complete open‑source ²¹⁰Pb sedimentation model designed for ephemeral systems, addressing limitations of legacy approaches developed for permanent lakes, and the development of low‑cost, flow‑proportional sediment sampling innovations that improve representativeness during peak flows.

To ensure broader uptake and long‑term impact, several enabling steps are identified:

- Further multi‑site demonstration of the SWAT+Gully framework to establish transferability across climatic and geomorphic settings.
- Continued open‑source development and documentation (model code, tracer workflows, protocols) to support adoption by researchers and agencies.
- Integration into decision‑support environments used by catchment managers, requiring collaboration with applied modelling and water‑quality platforms.
- Sustained investment in high‑frequency monitoring, as results demonstrate that extreme‑event dynamics are central to sediment and nutrient budgets under climate change.

Overall, the project delivers not incremental improvements but new ways of observing, tracing, and modelling sediment systems, positioning its outcomes for wide scientific uptake and long‑term influence on erosion science and catchment management.