# Contribution of airborne LiDAR on the mapping of vulnerability to groundwater pollution - Example of the drinking water catchment of Trépail

Julien Berthe, Olivier Lejeune, Jessy Jaunat, Pierre-Yves Ancelin, Alain Devos, Nicolas Bollot

► To cite this version:

Julien Berthe, Olivier Lejeune, Jessy Jaunat, Pierre-Yves Ancelin, Alain Devos, et al.. Contribution of airborne LiDAR on the mapping of vulnerability to groundwater pollution - Example of the drinking water catchment of Trépail. Symposium Transdisciplinary research for a healthy planet, Mar 2023, Reims, France. hal-04060236

HAL Id: hal-04060236

https://hal.science/hal-04060236

Submitted on 6 Apr 2023

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Contribution of airborne LiDAR on the mapping of vulnerability to groundwater pollution
## Example of the drinking water catchment of Trépail

<figure><img src="image_2.png" /></figure>

Julien Berthe, Olivier Lejeune, Jessy Jaunat, Pierre-Yves Ancelin, Alain Devos, Nicolas Bollot

GEGENAA 3795, Université de Reims Champagne-Ardenne, 57 rue Pierre Taittinger, 51100 Reims, France

<figure><img src="image_3.png" /></figure>

Symposium on March 30-31, 2023 Transdisciplinary research for a healthy planet

E.A. 3795

## Introduction

Airborne LiDAR is a laser tool that allows the creation of a high resolution DTM of the relief under the forest. Its application concerns archeology, geomorphology but also hydrogeology.

The objective of this study is to propose a method of mapping vulnerability to pollution adapted to the karst plateau under forest.

The EPIK approach, is created and tested for karstic environment. It's a multi-criteria spatial analysis based on superimposed and weighted indices allowing the zoning of the vulnerability to pollution.

This method is improved here with the lidar approach with the use of the Lidar tool which allows to better constrain each layer of spatial information.

<figure><img src="image_4.png" /><figcaption>Fig 1: operation of the airborne LiDAR</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig 2: EPIK method</figcaption></figure>

## Study area

The spring of Trépail is located in the eastern part of the Montagne de Reims. It emerges on the front of the cuesta of Ile-de-France characterized by the triptic forest, vinyard and culture.

It is a karstic spring captured for the drinking water supply of the

<figure><img src="image_6.png" /><figcaption>De la Nau
Sinkhole</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig 3: Map ou study area</figcaption></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /><figcaption>Fig 4: Geomorphological context of the Trépail spring</figcaption></figure>

## Methodology

### 2 : GIS treatment

<figure><img src="image_11.png" /><figcaption>Fig 5: EPIK methods with and without LiDAR</figcaption></figure>

### 3 : Production of EPIK parameters

<figure><img src="image_12.png" /></figure>

## Result

The resolution of vulnerability maps to groundwater pollution is improved by the use of lidar.

It also allows the creation of new layers that would not exist without LiDAR (more spatial information) and to improve the understanding of water flow.

This makes the epiK method operational at the cadastral parcel scale, and therefore operational from a regulatory point of view.

Thus, the Lidar allows an approach of the surface of feeding more coherent with the reality of the ground by including the impact of the ditches, by modifying the surface of the AAC and by detecting new zones of vulnerability.

<figure><img src="image_13.png" /><figcaption>Fig 7: Mapping of vulnerability of water pollution with EPIK method (with LiDAR)</figcaption></figure>

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /></figure>

<figure><img src="image_16.png" /></figure>

## Conclusion

The LiDAR data allowed to map a karstic border located on the slopes of the Montagne de Reims within the topographic watershed but also in the adjacent watersheds (hydrographic capture). Moreover, the LiDAR resolution allows to propose a vulnerability mapping at the parcel scale. As such, it can be applied to land development projects to achieve zero pollution in water.

Finally, the topographic survey by airborne LiDAR carried out by IGN, at the scale of France, whose data will be publicly available in 2026, seems to be of great interest for the creation and updating of PPCs and AACs, especially in karstic contexts.

## Bibliography

Berthe *et al.* (2022) Contribution of airborne LiDAR on the understanding of exokarstification factors in a low plateau context, example of the Montagne de Reims (France), *Géomorphologie*, Articles in press. URL : http://journals.openedition.org/geomorphologie/16829

Berthe *et al.* (2021) Imagerie LIDAR et cartographie semi-automatique de l'exokarst de la Montagne de Reims (Champagne, France), *Karstologia*, 78, p41-48 URL : https://hal.science/hal-03543184

Laurain (1985) Notice explicative de la feuille d'avize au 1/50 000, feuille 158, 35p.

Lejeune *et al.* (2007) Les Microcodium: un traceur naturel des écoulements karstiques dans les craies champenoises à proximité des formations paléocènes (Marne, France), *Karstologia 50*(1), p 1-8. DOI: 10.3406/karst.2007.2606

SAEFL (1998) Practical Guide - Groundwater vulnerability Mapping in Karstic Regions (EPIK), 56p