|M.Sc Student||Zweig Rachel|
|Subject||Quantification and Modeling of Land Degradation Processes|
in Arid Environments using Terrestrial Laser
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Sagi Filin|
|Dr. Yoav Avni|
|Full Thesis text|
Gullying is a principle agent of land degradation that causes substantial changes to the regional topography, sediment distribution, and vegetative cover. Gully growth, driven by backwards-headcut migration and gully incision, is the dominant mechanism for erosion processes in semi-arid environments. Gullying and other processes of land degradation occur both in natural settings and in regions that have experienced human interference, such as agricultural farms and terraced plots. On a regional scale these processes can have detrimental consequences on land use, water availability, and infrastructure stability.
Previous estimations of soil erosion processes in semi-arid to arid regions were limited to elementary documentation techniques which provided only a partial overview of the land degradation processes. This study introduces terrestrial laser scanning technology to document and analyze these processes with a significantly higher level of detail and resolution. The focus is on development of processes that facilitate detailed and accurate quantification of the land degradation elements, as well as the study of the added value of such data over alternative documentation techniques.
Five sites in the Negev Highlands are used as case studies for gully development in arid regions. These sites contain diverse features that are representative of the current regime of land degradation in both natural and human-altered landscapes. Between the years of 2009 to 2013, detailed three-dimensional data were collected after a variety of seasonal events. The datasets are analyzed using designated algorithms that were developed to expose the mechanisms that drive erosion and to quantify the geomorphic changes.
In the natural landscapes the results showed that the annual rates of headcut migration varied between 5.8 - 17.3 m and the annual soil loss varied between 87 - 1725 m3. In the terraced landscapes, the annual rates of headcut erosion were up to 1 m and the annual soil loss reached up to 8 m3. In the time since site abandonment, the headcut growth ranged between 40 to 240 m and the volume of soil eroded ranged between 562 - 3559 m3. They reinforce observations of an increased soil loss trend.
The continued monitoring of the gully complexes at these sites using terrestrial laser scanning provides insight into gully growth and development. Understanding the mechanisms and consequences of gullying and land degradation sheds light on the future progression of the Negev Highlands as an arid environment and contributes to the global discussion on desertification.