QGIS and Applications in Water and Risks

By Nicolas Baghdadi, Clément Mallet and Mehrez Zribi

Our four volumes propose to present innovative thematic applications implemented using the open source software QGIS. These are applications that use remote sensing over continental surfaces. The four volumes detail applications of remote sensing over continental surfaces, with a first one discussing applications for agriculture. A second one presents applications for forest, a third presents applications for the continental hydrology, and finally the last volume details applications for environment and risk issues.

• Language: English
• Publisher: Wiley
• Release date: Feb 14, 2018
• ISBN: 9781119476696

Book preview

Introduction

In the context of global changes (climatic and anthropogenic), the understanding and the quantification of the dynamics of water resources and risks of all types are essential for the managers of the territories in order to propose the most efficient solutions for planning and adaptation to changes. Geographic Information Systems (GIS) are invaluable tools in this domain. This is due to the sharply increasing use of remote sensing data, measurement networks and now products available to end users (several Copernicus services covering these issues are thus now mature).

This volume is devoted to the presentation and implementation under QGIS and its libraries of case studies dealing with water and risk issues. Chapters 1 and 2 discuss the application to bathymetry mapping. Chapters 3–5 are devoted to hydrological problems, both from a surface (reservoirs) and a linear (networks) point of view. Chapters 6–8 are dedicated to the presentation of three types of risks arising from very different hazards (drought, crop pests, erosion).

This volume, supported by scientists internationally renowned in their fields, aims to update readers’ knowledge and to describe the main research and development issues for forthcoming years. It is intended for research teams in geomatics, second-level (engineering schools, master’s degrees) and postgraduate studies (PhD students), and engineers involved in the management of water and territory resources. In addition to the texts of the proposed chapters, the readers will have access to the data and tools, as well as all screenshots related to the QGIS application in order to smoothly carry out each step of each application.

A supplement to the chapters, including datasets and screenshots illustrating the practical application of the chapters, is available at the following address:

Using Internet Explorer: ftp://193.49.41.230

Using a FileZilla client: 193.49.41.230

Username: vol4_en

Password: 334@Volne

We would like to thank everyone who contributed to the development of this book; first of all, the scientists, authors of the chapters of course, but also the experts of the scientific committee for their inspection of the chapters and the corrections made. This project was carried out thanks to the support of IRSTEA (French Research Institute for Science and Technology for Environment and Agriculture), CNRS (French National Center for Scientific Research), IGN (National Institute for Geographic and Forest Information) and CNES (French National Center for Space Studies).

We are very grateful to Airbus Defense and Space and Equipex Geosud for providing us with SPOT 5/6/7 images. Please note that these images may only be used in a research and training framework and any commercial activity based on the data provided is strictly prohibited.

Our thanks also go to our families for their support in realizing this project and to André Mariotti (Professor Emeritus, Pierre and Marie Curie University) and Pierrick Givone (President, IRSTEA) for their encouragement.

Nicolas BAGHDADI

Clément MALLET

Mehrez ZRIBI

1

Monitoring Coastal Bathymetry Using Multispectral Satellite Images at High Spatial Resolution

1.1. Definition, context and objective

In this chapter, the instantaneous water depth (H), which assumes a negative value, is defined as the vertical distance from the water surface to the bottom at a given time. In coastal shallow waters associated with tidal environments, the variations of H depend first on the phase of the tide. The water height due to the tide (T), which usually assumes a positive value, can be calculated from a local tidal datum, which provides standard elevations with respect to a reference level (To; for instance, To is defined as the lowest astronomical tide for the France Hydrographic Service, SHOM).

The bathymetry (Z) is the vertical distance from the water surface to the bottom, corrected from the tide level. For more information, the reader can refer to the publication of the International Hydrographic Organization on the standards for hydrographic surveys¹. Following the previous definitions, the relationship between Z, H and T is then given by:

[1.1]

When |H| > |T|, the value of Z is negative meaning that the bottom elevation is lower than the reference elevation of the tidal datum (Figure 1.1, case 1). In the other cases, Z assumes a positive value that means the bottom elevation is higher than the reference elevation (Figure 1.1, case 2).

Figure 1.1. Schematic description of the main parameters used to characterize the water height in coastal shallow waters: instantaneous water depth (H), tidal height at a given time (T) and bathymetry (Z). For a color version of the figure, see www.iste.co.uk/baghdadi/qgis4.zip

Bathymetry is a key environmental parameter for studying and modeling the hydrodynamics, the sediment transport and the long-term morphological evolution of coastal systems as well as for predicting their responses to hydroatmospheric maritime hazards and assessing their vulnerabilities to environmental risks. The accurate and regular measurement of bathymetry is therefore a major scientific issue with strong socioeconomic