Events & Theses

Public thesis defense of Eric LUTETE LANDU

"Effectiveness of measures aiming to stabilize urban gullies in tropical cities: lessons learned from failures and successes in the D.R. Congo."

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Abstract

[EN]
Urban gully erosion is a growing problem in many tropical cities of the Global South, including those in the Democratic Republic of Congo, where thousands of urban gullies cause significant damage. A survey conducted among 802 households in Kinshasa revealed that 60% of them experienced damages for an average cost of around $4,320 per affected family. Although many failures have been reported in the various initiatives currently implemented to stabilize gullies, a detailed analysis of some of these measures, particularly runoff retention structures and vegetation, shows the great potential they offer. In the first case, if implementation is well-coordinated and in the second case, if species are carefully selected and combined with other stabilization efforts.
[FR]
L'érosion des ravins urbains est un problème croissant dans de nombreuses villes tropicales du Sud, y compris celles de la République Démocratique du Congo, où des milliers de ravins urbains causent des dégâts considérables. Une enquête menée auprès de 802 ménages à Kinshasa montre que 60% d’entre eux ont enregistré des dommages qui s’élèvent en moyenne à environ 4 320 $ par famille affectée. Bien que beaucoup d’échecs soient observés dans la multitude d’initiatives mises en oeuvre actuellement pour stabiliser les ravins, une analyse détaillée de certains d’entre eux, notamment les structures de rétention de ruissellement et la végétation, révèle le grand potentiel qu’offrent ces mesures si dans le premier cas leur mise en oeuvre est bien coordonnée, et dans le second si les espèces sont bien sélectionnées et combinées à d’autres efforts de stabilisation.

Jury Members

Prof. Dr. Fils Makanzu Imwangana (Promoter, Université de Kinshasa)
Prof. Dr. Matthias Vanmaercke (Co-Promoter / de facto Promoter, KU Leuven)
Prof. Dr. Aurélia Hubert (Administrative Promoter, Secretary, ULiège)
Prof. Dr. Charles Bielders (Co-Promoter, Université catholique de Louvain)
Prof. Dr. Aurore Degré (Chair, ULiège)
Prof. Dr. Amaury Frankl (Jury member, Universiteit Gent)
Prof. Dr. Raymond Lumbuenamo Sinsi (Jury member, Université de Kinshasa)
October 28th,

Public thesis defense of Timothée CLÉMENT

"Effectiveness of conservation cropping practices in mitigating runoff, soil erosion, and pesticide surface losses in Northwestern Europe"

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Abstract

Soils of the Western European loess belt are intensively cultivated and particularly prone to runoff and soil erosion. Besides threatening soil resources, overland flows cause muddy floods that damage infrastructure downstream and pollute water bodies by transferring nutrients and pesticides. Numerous conservation farming practices are known to mitigate surface flows, but the magnitude of their effectiveness remains uncertain in Northwestern Europe. Based on a systematic review and meta-analysis, we estimated the runoff and erosion mitigation effects of conservation (i.e., non-inversion) tillage, winter cover crops, and tied-ridging (i.e., micro-basin tillage in potato fields). These conservation practices decreased seasonal soil losses by 66%, 72%, and 92%, respectively, compared to conventional tillage. For conservation tillage, we further identified key factors explaining the variability of the flow mitigation effects, including the time since ploughing was stopped, the type of implemented conservation tillage scheme (e.g., number of operations), and the main crop type (winter or spring crop). Besides its use in potato crops, micro-basin tillage has also recently been developed in Belgium for maize crop, using an innovative agricultural roller designed to shape depressions in-between the maize rows. Based on past plot experiments, micro-basin tillage in maize was found to reduce runoff (-69%), soil erosion (-83%), and associated pesticide transfer (e.g., -65% for the active ingredient flufenacet). Lastly, two uncommon conservation practices in Northwestern Europe were investigated through original plot experiments in maize crops:  undersowing and strip-tillage. Undersowing (simultaneous sowing) red fescue or white clover in maize was very challenging in terms of weed control and resulted in no mitigation effect on surface flows compared to a conventionally tilled sole maize crop. Strip-tillage (i.e., tine-tilling the maize row only) significantly decreased runoff (-31%) and soil erosion (-60%). A hydrological process-based model was further calibrated based on the measured flow data in strip-tilled and conventionnaly-tilled maize plots. Subsequently, a scenario analysis was conducted to assess the conservation potential of the strip-tillage technique under extended climate, soil and slope conditions. Simulations reveal that strip-tillage cultivation would halve both the mean erosion rate as well as the flood risk (maximum daily runoff), as compared to conventional tillage. Unfortunately, available data did not allow to evaluate the impact of conservation practices on pesticide transfer in a conclusive way, neither from the quantitative review nor from our field trials. Meanwhile, the outcomes of this thesis can assist farmers, farm advisors or policy makers in (promoting) the implementation of effective conservation farming practices. 

Jury Members

Prof. Emmanuel HANERT (Chairman- UCLouvain)

Prof. Charles BIELDERS (Supervisor - UCLouvain)

Prof. Marnik VANCLOOSTER (secrétaire - UCLouvain)

Prof. Aurore DEGRE (ULiège Gembloux Agro-Bio Tech)

Prof. Wim CORNELIS (UGent)

Dr. Bruno HUYGHBAERT (CRA-W)

Public thesis defense of Nathan BEMELMANS

"Influence of pesticides on trace element transfer in the soil-solution-plant systems : a focus on glyphosate and tebuconazole"

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Abstract

TBA

Jury Members

Prof. Yannick AGNAN (UCLouvain, Supervisor)

Prof. Lionel ALLETTO (INRAE)

Dr Maryse CASTREC-ROUELLE (Sorbonne Université)

Prof. Stanley LUTTS (UCLouvain)

Dr Benoît PEREIRA (EREA)

Prof. Marnik VANCLOOSTER (UCLouvain, Chairman)

Public thesis defense of Sandratra Zonirina (Zo) RAMAHAIMANDIMBY

"Fonctionnement et altérations hydrologiques du bassin d’Ankavia (Madagascar) dans une perspective de gestion intégrée des ressources en eau."

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Abstract

Humid tropical environments, particularly the SAVA region in northeastern Madagascar, face important challenges in water resource management, exacerbated by land-use changes and climate modifications. Effective operationalization of Integrated Water Resources Management (IWRM) is imperative to develop sustainable approaches that reconcile current needs with resource preservation for future generations. However, its effective implementation is hindered by a lack of reliable hydrometeorological data and insufficient understanding of local hydrological processes. This study focuses on the Ankavia watershed, representative of the region, to elucidate its hydrological functioning and analyze its alterations in the face of environmental changes. A multiscale and interdisciplinary methodological approach was adopted, integrating analyses at different spatial and temporal scales, from micro-basin to large watershed, and covering periods ranging from isolated rainfall events to medium-term (2050) and long-term (2100) climate trends. The study identifies IMERG satellite data as a reliable alternative to ground rain gauges, while emphasizing the importance of continuing ground measurements. It reveals that land cover, particularly forest cover, as well as pedological and geological characteristics, strongly influence water flows. Future hydrological alterations are shown to be driven mostly by climate change rather than land uses changes. These results can serve as a solid foundation for IWRM adapted to the SAVA region and similar areas, addressing the growing challenges of environmental and climate changes.

Jury Members

Prof. Emmanuel HANERT (UCLouvain - Chairman)

Prof. Charles L. BIELDERS (UCLouvain - Supervisor)

Dr. Alain RANDRIAMAHERISOA (Université d’Antananarivo, Madagascar - Co-supervisor)

Prof. Marnik VANCLOOSTER (UCLouvain - Reader)

Prof. François JONARD (Université de Liège - Reader)

Prof. Sandra Soarez FRAZAO (UCLouvain  - Reader)

Dr. Quentin GOOR (Chargé de cours UCLouvain - Reader)

Public thesis defense of Louis DELVAL

"Quantifying soil-grapevine hydraulics from plant to field scale."

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Abstract

Grapevine (Vitis vinifera) is the world’s third most valuable horticultural crop. Today, climate change significantly threatens grape productivity, notably due to more frequent and extended drought periods. To address the critical issue of grapevine response to water stress, soil-plant hydraulic processes can be considered the cornerstone of the physiological mechanisms involved in grapevine tolerance to drought. Although recognized, the key role of belowground hydraulics on grapevine water status is rarely addressed because difficult to measure. This PhD thesis aims to understand how soil-grapevine hydraulics impacts the transpiration rate, water potential and root water uptake of in situ grapevine cv. Chardonnay. At the plant scale, we first revealed experimentally that the transpiration control of grapevine is soil texture specific and is triggered by a decrease of belowground hydraulic conductance, rather than xylem cavitation in the stem. We also highlighted the coordination of short-term hydraulic responses with longer-term growth strategies. Then, by using a biophysical model representing explicitly the series of hydraulic conductances between the bulk soil and the stem, we demonstrated that, during drought, root water uptake is mainly limited by the rhizosphere in coarse-textured soil, while it is the root system that controls root water uptake in fine-textured soil. Finally, a field scale experiment, in non-irrigated vineyards, provided evidence that the spatial distribution of grapevine leaf water potential is mainly governed by the within-vineyard soil hydraulic conductivity heterogeneity, especially during drought. By quantifying soil-grapevine water relations in different edaphic conditions during drought, this PhD thesis provides insights that could help winemakers to ensure better adaptation to climate change and enhance vineyard resilience.

Jury Members

Prof. Mathieu JAVAUX (promoteur - UCLouvain)

Prof. François JONARD (co-promoteur - UCLouvain)

Prof. Marnik VANCLOOSTER (président du jury - UCLouvain)

Prof. Xavier DRAYE (Secrétaire du jury - UCLouvain)

Prof. Bruno DELVAUX (UCLouvain)

Prof. Cornélis VAN LEEUWEN (Bordeaux Sciences Agro)

Prof. Jan VANDERBORGHT (Forschungszentrum Jülich et KULeuven)

Public thesis defense of Jean BOUCHAT

"Maize green area index retrieval from multistatic and multi-frequency SAR data"

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Abstract

Climate change and a rapidly growing world population are placing an ever-increasing pressure on the agricultural sector. In this context, green area index (GAI) monitoring plays an essential role in assessing the status and health of crops, making it a key source of information for farmers and decision-makers alike. Current operational methods for GAI monitoring rely mainly on optical imagery, and are therefore hampered by the recurring presence of clouds. Synthetic aperture radars (SARs) present a promising alternative for collecting data in almost all weather conditions. The main objective of this thesis is to improve the retrieval of the GAI in maize crops using SAR remote sensing, with a perspective towards near real-time, large scale crop monitoring. To this end, the potential of multistatic and multi-frequency SAR for crop monitoring is assessed using experimental data, and methods are developed for GAI retrieval from SAR data, both alone and in conjunction with optical imagery. The results of these investigations suggest that further efforts should be made to integrate SAR remote sensing, either as a complement or entirely on its own, into current crop monitoring systems to improve their temporal resolution, timeliness, and overall reliability, thereby contributing to food security.

Jury Members

Prof. Pierre DEFOURNY (UCLouvain, Belgium), supervisor

Prof. Marnik VANCLOOSTER (UCLouvain, Belgium), chairperson

Prof. Xavier DRAYE (UCLouvain, Belgium), secretary

Dr. Dominique DERAUW (Liège space centre, Belgium)

Prof. Leila GUERRIERO (Tor Vergata University of Rome, Italy)

Public thesis defense of Camille GUISSET

"Climate and drought response of four non-native tree species in their area of introduction in Wallonia."

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Abstract

TBA

Jury Members

Prof. Quentin PONETTE (supervisor) – UCLouvain

Prof. Caroline VINCKE (supervisor) – UCLouvain

Prof. Emmanuel HANERT (chairperson) – UCLouvain

Prof. Nathalie BREDA – INRAE (France)

Prof. Xavier DRAYE– UCLouvain

Prof. Mathieu LEVESQUE – ETH Zurich (Suisse)

Public thesis defense of Céline LAMARCHE

"Assessing 29 years of global land cover dynamics from satellite Earth Observation"

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Abstract:

Land use and land cover change contribute significantly to anthropogenic CO2 emissions and biodiversity loss. However, current inventory-based statistics miss year-to-year land changes, preventing a comprehensive global understanding.

Earth observation by satellite provides valuable information for mapping global annual changes at the pixel level. Yet, consistency is crucial to capture change signals among variability from natural surface fluctuations or evolving satellite mission capabilities. In this thesis, we co-develop and evaluate the very first global annual land cover change time series at 300 m from 1992 to 2020, maintaining consistency across space, time and satellite missions. This dataset, currently used for Intergovernmental Panel on Climate Change (IPCC) climate modeling and Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) analysis, enables us to quantify and analyze the global dynamics of land cover change over the last 30 years.

This research also contributes to enhancing the qualification of land cover datasets. While validation guidelines are well-established for individual product assessment, we introduced a stratified random sampling method for product benchmarking, tailored to areas prone to discrepancies between products, to highlight the satellite product strengths and weaknesses. To improve climate and land surface, we enabled the conversion of land cover categories to plant functional types (PFT) composition per pixel. This was made possible thanks to the development of a globally applicable framework to seamlessly integrate multiple high-resolution datasets that might otherwise not be compatible.

Finally, we investigate the impact of uncertainty in Earth observation surface reflectance measurement on the categorical land cover classification process. Building on a Monte Carlo simulation, we quantify errors and propose a classification ensemble approach to effectively mitigate them.

This work contributes to more informed land accounting in the context of rapid anthropogenic change and climate evolution, supporting the assessment of the Food and Agriculture Organization (FAO) and Organization for Economic Co-operation and Development (OECD) environmental-economic accounting systems.

Jury members:

Prof. Pierre DEFOURNY (Supervisor)

Prof. Patrick BOGAERT (Secretary)

Dr. Gregory DUVEILLER (Max Planck Institute for Biochemistry, Germany)

Dr. Martin Stefan BRANDT (University of Copenhagen, Denmark)

Prof. Emmanuel HANERT (President)

Public thesis defense of Imen EL GHOUL

"Combined effects of climate and land use change on the hydrology of a Mediterranean catchment: the Siliana catchment in Tunisia."

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Abstract

Climate change and Land use/land cover (LULC) represent the two primary factors influencing the hydrology of a watershed. In this research, we explore the combined impact of alterations in climate and LULC on hydrological processes. This examination involves comparing the baseline period (1979-2005) with future conditions (2046-2072) within the Siliana catchment in Tunisia, utilizing the Soil and Water Assessment Tool (SWAT) hydrological model.

Future LULC scenarios are generated using Cellular Automata (CA)-Markov chain modelling, while climate change scenarios are derived from regional climate models (RCMs) developed within the coordinated regional climate downscaling experiment (CORDEX-Europe). To address bias, the so-called Cumulative Distribution Function (CDF) matching approach is applied using observed precipitation and temperature data. Subsequently, bias-corrected climate projections and future LULC scenarios are input into the SWAT model to evaluate changes in catchment hydrology, based on various hydrological indicators (such as monthly discharge and total water availability). Prediction uncertainty associated with changes in LULC, climate conditions, and SWAT model parameters is also assessed.

The findings indicate that the Siliana catchment area is projected to experience a warmer and drier climate, leading to altered hydrological conditions in the future. This climatic shift is expected to result in a significant decrease in rainfall, consequently reducing surface runoff, water yield, and groundwater levels. Moreover, the hydrological modifications are consistent with the observed temperature patterns in the catchment region. The anticipated rise in average temperatures will likely lead to a substantial increase in potential evapotranspiration (PET).

Regarding changes in land use and land cover (LULC), there is an expectation of a notable decline in pastureland and an increase in irrigated areas, shaping the future LULC composition relative to baseline conditions.

Interestingly, the impact of climate change alone is expected to have a more pronounced effect on hydrological responses compared to the combined influence of climate and changes in LULC. This suggests that modifications in land use within the Siliana catchment region lead to an attenuation effect marked by extended periods of high-flow events, a reduction in the intensity of peak high-flow events, and an increase in the occurrence of low-flow events.

Jury members:

Prof. Marnik VANCLOOSTER (UCLouvain), supervisor

Prof. Slaheddine KHLIFI (Ecole Supérieure des Ingénieurs de Medjez El Bab, Tunisie), supervisor

Prof. Emmanuel HANERT (UCLouvain), president

Prof. Bas VAN WESEMAEL (UCLouvain), secretary

Prof. Isabelle LA JEUNESSE (Université de Tours, Fr.)

Dr. Haykel SELLAMI (Centre de Recherche et des Technologies des Eaux, Tunisie)

Dr. Taoufik HERMASSI (Institut national de la recherche en génie rural eaux et forêts, Tunisie)

Public thesis defense of Arthur SLUYTERS

"An Integrated Development Environment for Gesture-based Interactive Applications: Instantiation to Radar Gestures by Arthur Sluyters"

Imagine controlling your TV or Virtual Reality headset with just a flick of the hand, as easily as swiping on your smartphone. These gestures, known as “mid-air” gestures, are closer than you may think, thanks to recent technological improvements. They offer plenty of benefits compared to more traditional input methods, by allowing greater freedom of movement, eliminating the need for physical touch, and making interactions feel more natural and enjoyable.

However, mid-air gestures come with a unique set of challenges. First, how can we accurately capture and interpret these movements in real-time? The system should be lightning-fast, reliable, and intuitive, without imposing constraints on the user. Then, how should we integrate these gestures into everyday applications? Crafting a highly usable gesture-based interface currently requires many hard-to-come-by skills, including expertise in gesture recognition, application development, and user experience design.

This thesis directly addresses these challenges by proposing innovative solutions to foster the development of gesture-based interfaces, in the form of tools and methodologies. Our exploration focuses on the use of radar sensors for gesture recognition, which boast a compact form factor, low power consumption, and the ability to detect gestures through solid surfaces and in challenging lighting conditions, all while preserving user privacy.

Jurys members:

Prof. Sébastien Lambot (UCLouvain), supervisor

Prof. Jean Vanderdonckt (UCLouvain), supervisor

Prof. Peter Van Roy (UCLouvain), chairperson

Prof. Suzanne Kieffer (UCLouvain), secretary

Prof. Luis A. Leiva (University of Luxembourg, Luxembourg)

Prof. Paolo Roseli (University of Rome ‘Tor Vergata’, Italy)