Project description
Context
Urban greening along with integrated stormwater management, that involves both limitation of soil sealing and on-site runoff control, offer perspective for adapting cities to climate change while simultaneously reducing their environmental footprint. Today, urban stormwater management increasing rely on pervious and vegetated devices, disseminated throughout the city, as a complement to historical piped-based systems. Soil and vegetation hence play an increasing role for the limitation of stormwater discharge to surface waters. Such a change also provides opportunities for the replenishment of soil and ground water reserves or to ensure water availability for the urban vegetation.
The role of soil and vegetation in the hydrology of urban catchments has been demonstrated in previous studies (Pophillat et al., 2022). Yet, its consideration in research or real-world applications (e.g., to anticipate water transfers) is hampered by difficulties in describing the complexity of the urban underground compartment, often heavily reworked and including various infrastructures (networks, basements…) (Bonneau et al., 2017). In view of the strong expectations of partitioners or decision-makers for the assessment and development of stormwater management strategies, as well as the questions raised by the growing presence of vegetation in a changing climate and increasing water-scarcity context, investigating how to better describe this role is essential.
Hydrological models can be relevant decision-support tools for stormwater management and integration of water in urban planning, as long as they incorporate an appropriate description of the processes involved (Ferrans et al., 2022; Pophillat et al., 2021). From this perspective, spatially distributed hydrological models are of particular interest given their ability to simulate the impact of changes in land use or drainage infrastructures within urban environments. Their implementation however still faces difficulties due to the limited knowledge about the level of detail required to properly represent some underground or near surface processes (Golden and Hoghooghi, 2018). In practice, this level of detail is often guided by i) the availability of data for the description of the different compartments (geology, soil characteristics, land use and subsoil, characteristics of infiltration structures, built envelope… etc.) and ii) the structure of the models.
Objectives
The objective of this thesis is to analyze how to best adapt the representation of urban catchments in hydrological models to the level of information available from geographic databases. Model implementation strategies (regarding spatial or temporal discretization, modeling scheme, parameterization…) will be developed for contexts characterized by limited descriptive information, such as real-world engineering applications, and the consequences of the lack of information on the reliability of model output be examined. Special attention will be given to the description of the underground compartment and stormwater management systems, for which a detailed characterization often becomes burdensome as the size of studied catchment increases.
Proposed methodology
The URBS model (Rodriguez et al., 2008; Pophillat, 2022) will be used to test different options regarding i) the description of the characteristics of the urban environment and ii) the schemes used to simulate hydrological processes. The model will be applied to various case studies for which hydrological observations are already available, in order to test the effect of the level of detail in the description of the urban environment on the ability to reproduce the observed hydrological functioning. Different description strategies will be developed, based on geographical data, under contrasting assumptions as to their availability. These strategies will be evaluated on the basis of hydrological observations and compared with results obtained in an “optimal” knowledge context, for which all available information is mobilized.
At this stage, the following study-sites have been identified: i) In Nantes, a 30-hectare residential catchment area (Pin Sec) and an eco-neighborhood with on-site stormwater management facilities, both monitored by IRSTV as part of the ONEVU research observatory; ii) in the Paris region, a 330-hectare district under development within the Paris-Saclay urban campus, studied since 2010 by Cerema (Pophillat 2022).
Supervisions and conditions
The thesis will be supervised by Fabrice Rodriguez (Université Gustave Eiffel) and Jérémie Sage (Cerema). Fabrice Rodriguez will be the Ph.D. director.
The Ph.D. student located at the Water and Environment laboratory (Laboratoire Eau et Environnement) on the Bouguenais site of Univ. Gustave Eiffel, nearby Nantes. The Ph.D. student will be enrolled at the école doctorale « Matière, Molécules, Matériaux & Géosciences ».
Expected skills:
- Solid background in environmental sciences and hydrology.
- Aptitude for scientific programming (e.g., python, Matlab, R…).
- Experience with GIS and geodata processing.
- Statistics and data (including timeseries) analysis techniques.
References
Bonneau, J., Fletcher, T.D., Costelloe, J.F., Burns, M.J., 2017. Stormwater infiltration and the ‘urban karst’ – A review. Journal of Hydrology 552, 141–150. https://doi.org/10.1016/j.jhydrol.2017.06.043
Ferrans, P., Torres, M.N., Temprano, J., Rodríguez Sánchez, J.P., 2022. Sustainable Urban Drainage System (SUDS) modeling supporting decision-making: A systematic quantitative review. Science of The Total Environment 806, 150447. https://doi.org/10.1016/j.scitotenv.2021.150447
Golden, H.E., Hoghooghi, N., 2018. Green infrastructure and its catchment-scale effects: an emerging science. WIREs Water 5, e1254. https://doi.org/10.1002/wat2.1254
Pophillat, W., Sage, J., Rodriguez, F., Braud, I., 2022. Consequences of interactions between stormwater infiltration systems, shallow groundwater and underground structures at the neighborhood scale. Urban Water Journal 19, 812–823. https://doi.org/10.1080/1573062X.2022.2090382
Pophillat, W., Sage, J., Rodriguez, F., Braud, I., 2021. Dealing with shallow groundwater contexts for the modelling of urban hydrology – A simplified approach to represent interactions between surface hydrology, groundwater and underground structures in hydrological models. Environmental Modelling & Software 144, 105144. https://doi.org/10.1016/j.envsoft.2021.105144
