+ Introduction to mapping units theory and practice + How to Build, edit and run a Graphical modeler tool in QGIS? + How to run QGIS modeler to integrate thematic maps with training/ testing landslides data

1. Automatic Delineation of Grid based and Geo-Morphological
Slope Units for Susceptibility Mapping
Analysis
Omar F. AlThuwaynee, PhD. Eng.

2. Thank you!
To download the QGIS tools and watch the entire course entitled:
A u t o m a t i c D e l i n e a t i o n o f G r i d u n i t s a n d G e o - M o r p h o l o g i c a l
S l o p e U n i t s f o r S u s c e p t i b i l i t y M a p p i n g A n a l y s i s
Visit:
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Full course:
www.udemy.com/user/omar-f-althuwaynee/ Omar F. AlThuwaynee |
Dr. Eng. GIS & Geomatics Engineering
For any inquiries, write to me: scadac@outlook.com

3. Susceptibility mapping process consist of :
1. Data
• Independents (categorial or continuous)
• Dependent (points or polygons)
2. Analysis model
• Bivariate, multivariate, ANN, fuzzy logic, DT and ensemble algorithms..
3. Results representation
4. Validation
Q/ how to increase the results accuracy level?
• Representation types (points or polygons)
• Mapping unit size and shape (how different mapping unit effect the )
• Free slides areas selection
• Sampling methods (random, geographical or temporal)
• More data
STEPS: The Mapping Unit
Manual construction of Susceptibility
mapping process is time consuming
and move the data from one package
to another will aggregate the
uncertainty.

4. Past is the key to the future, what happened before in specific area might probably
happen again when the previous circumstances met.
On the contrary, some places will never have chance to develop or witness landslides.
Free slides areas:
• Literature mentioned about where (ex, slopes < 5°) and how to select landslides free
area (randomly or spatially).
• But what about the approximate areas of the free landslides training data?
• Using any type of regression as well as other data mining approaches, we need binary
values for dependent factor (0,1).
• I.E the number of events (points and polygons) as well as the area (in case of
polygons features) should be equivalent as much as possible.
STEPS: The Mapping Unit

5. • The mapping unit is the smallest non-separable spatial entity within a hazard assessment,
and data extraction is based on spatial primitives.
• The accuracy of the data depends on the partitioning of the mapping unit.
• The mapping units, which can be regular or irregular primitives, are generally divided into
the following five categories:
1. grid cells,
2. slope units,
3. terrain units,
4. unique-condition units
5. topographic units.
• The selection of meaningful mapping units is of great importance for susceptibility zonation
• Mapping units should maximize internal homogeneity
• In literature, best compromise between landslide size and landslide conditioning variables
using a range of spatial resolutions from 50 to 100 m (AUC of the receiver operating
characteristic values higher than 80%) (Application of a GIS-based slope unit method for landslide
susceptibility mapping along the Longzi River, southeastern Tibetan plateau, China)
STEPS: The Mapping Unit

6. Choosing the most appropriate mapping unit depends on a number of factors
• the type of landslide phenomena
• the scale of the investigation;
• the quality,
• resolution,
• scale and type of the thematic information required;
• availability of adequate information management and analysis tools.
The factors are mandatory for the reliability of any landslide zoning procedure (Calvello,
Cascini et al. 2013)
STEPS: The Mapping Unit

7. Table 1(Calvello, Cascini et al. 2013)
STEPS: The Mapping Unit

8. • Dividing the area into regular square grid cells
• Grid-based cells: loss of any terrain-related information and
neighborhood relations (destroys the integrity of the slope)
Example: For overlay analysis the entire study area was overlaid with
10 x 10 m polygonal grid cells.
• Grid-based: loss of any terrain-related information and
neighborhood relations when using grid cells
Mapping units: Grid units

9. Scale of analysis.
• The minimum area of terrain units for computational purposes at a given scale (TCUs) is smaller
than the minimum area dependent factor, because the minimum area of a TCU is related to the
‘spatial resolution’ of the map,
• I.e. the measure of the smallest area identifiable on the map as a discrete separate unit, whereas
the minimum area of a TZU is related to the desired ‘informative resolution’ of the zoning.
Ex: regular square (grid units) commonly used dimension of cell size is 1/1000 of the scale factor, such
that the area covered by each elementary pixel increases as the scale of analysis decreases
whereas, regardless of the scale, the size of each square cell on paper is always 1×1 mm.
Mapping units: appropriate cell size

10. Defined by intersecting slope terrain units, i.e. the
intersection between the networks of drainage lines and
ridges derived from a DEM in the area
• An algorithm that considers both the drainage network
and the geology of the area to define the homogenous
units.
Mapping units: Terrain unit (hydro-geological units)

11. 1. Acquired by means of geomorphic units and watershed classifications (from RS
data and DEMs).
2. Retains the integrity of the geological units truly reflect the geomorphological
characteristics of a landslide and the spatial characteristics of the valley.
3. The evaluation process is able to reflect the spatial characteristics and physical
mechanisms responsible for the landslide, therefore improving the reliability of
the evaluation results
4. represents the basic unit for assessing landslides, collapses, and other
geological disasters.
5. For all the influence factors, the developmental stage of valleys and rivers plays
an important role in the formation of landslides and collapses.
6. the slope unit ensures that the evaluation results are more perceptive of the
reality
7. as portions of land slope with the general requirement of maximizing
homogeneity within each unit and heterogeneity between different units
8. the high dimensionality of grid-based prediction is summarized from million
pixels to thousands thus reducing the associated computational burden.
Mapping units: Slope unit

12. • Aspect does not create units within on aspect of slope
• In slope unite, we divide the slope based on the watershed
and it can be more than unit in one aspect
• slope unit to maximize the aspect homogeneity
• By increasing the contribution area (estimation) of watershed.
We get higher density slope unit and vis versa
• While in slope aspect we have a fixed representation based
on the variation in the slope direction only,
https://www.reddit.com/r/dataisbeautiful/comments/1bdop4/slopeaspect_map_oc/
http://priede.bf.lu.lv/ftp/pub/GIS/gis_paketes/MicroDEM/About_files/aspectdegree.jpg
Mapping units: Slope unit and Aspect unit

13. • regular grid cells, rapidity and simplification were achieved during computer processing.
• unrelated to the geological, geomorphological, or other spatial terrain information.
• Since the area of the slope unit is much larger than that of the grid cell, equalization
phenomena persist during the extraction of the influential factors using the slope unit
• to the quantification of watershed geomorphic factors, so that the evaluation process can
preferably elaborate the physical mechanisms of landslides, thus improving the reliability of
the evaluation results Application of a GIS-based slope unit method for landslide susceptibility mapping along the Longzi River, southeastern Tibetan plateau, China
• The slope angle obtained through the grid cell varies greatly in concentration, not
considering the integrity of the landslides.
• the topographic relief is the most representative feature of the slope unit, which
can efficiently express the fluctuation of landslides.
STEPS: PROS AND CONS

14. STEPS: Non landslide samples
• LSM process using machine learning algorithms can be considered sampling of two
groups of data
• namely landslide (1) and non-landslide (0),
• whole study site excluding landslides occurred zones, areas on the river channel and
places having slope angles between 0° and 5° were considered as non-
landslide areas, as suggested in previous studies (Gómez and Kavzoglu 2005).

15. • SUs can be defined by manual procedures (which are intrinsically error-prone and
subjective) or by using semi-automatic process.
• We used the Python Modeler embedded code for SU delineation to be used in the
QGIS (A Free and Open Source Geographic Information System) environment.
• The method defines SUs bounded by hydrological drainage and divide lines,
maximizing the intra-unit (internal) homogeneity and the inter-unit (external)
heterogeneity of the slope aspect.
• For a given landscape, no unique SU delineation exist exists as it depends on the
purpose of the study and the scale at which the study is carried over.
• For that reason the user can define: (i) the required degree of homogeneity within
each SU with the
• An automatic delineation of SUs reduces the subjectivity and time
STEPS: Methodology

16. The slope unit is consider as half of the catchment basin
• the catchment basin can be divided into two slope units according to
the crest line and the valley line.
• Drainage network generated with a given threshold of contributing
area can be arbitrarily dense
Bottom-up approach vs. top-down approach:
– bottom-up starts from a fine partition of the slopes, then group together
similar units. Typically based on image (aspect) classification
– top-down based on pure hydrologic partition into half-basins, with
smaller contributing area providing finer partition (adopted here)
STEPS: Methodology

17. Methodology: Algorithm development steps
1. the drainage network (i.e., the valley line) is extracted
from the original DEM data in order to generate the
catchment basin in positive relief through the hydrological
analysis module in QGIS.
2. the original DEM data is inverted, wherein the highest
point becomes the lowest point and vice versa.
3. According to the same method, the drainage network (i.e.,
the crest line) is extracted according to the negative relief,
thereby generating the catchment basin.
4. Finally, the two catchment basins obtained using the
positive and negative reliefs are superimposed and
merged
As a consequence, two slope units of the catchment basin are
acquired.
In this course, I will show the automatic process to
produce the grid and slope units

18. STEPS: Technical ISSUES
QGIS Software version 2.18.16 PC specifications
– 64 bit
– 32 bit

19. SAMPLING STRATEGIES: Common steps
1. Extract the files out of the zip folder
2. Copy the attached folder to specific location
> C:Usersuser.qgis2processing
3. open QGIS, and click on processing Toolbox, now the models appeared.
4. Using GRID based
Create slides and non-landslides training and testing points
5. Using Slope Units based
Create slides and non-landslides training and testing points

20. 1.D –Option 1- Non Landslides areas [ Area> (Mean –SD), Area <(Mean+SD)]
PS: if the area has small range, you may get the following message [Error executing algorithm
Random extract Selected number is greater than feature count. Choose a lower value and try again.]
Solution: widen the range of non landslides area
-Option 2- Non Landslides areas [ Area>first quartile, Area < third quartile]
2. Training and testing
PS: grid= cell size of DEM or larger
extent: choose the original slope
SAMPLING STRATEGIES: Grid (pixel) based units

21. STEPS: Technical ISSUES
GRASS crash
– Problem: When I try to run a grass or a grass 7 script, I've the following message
Problem executing algorithm environment can only contain strings. See log for more details
Solution:
– Switch to QuickMapService Plugin and removing Openlayers plugin, this makes grass
modules work again. https://issues.qgis.org/issues/15234
• Topology clean
break the complex areas into single areas
• Extract by expression
If you need homogenous cells use this formula ($area > 1st quartile AND $area < 3rd
quartile)

22. STEPS: Summary
Along the current course, we discussed the followings:
1. introduction about mapping units and explained the main mapping units
2. explained the relationship between the study area scale and raster pixel dimension,
and how to chose the most suitable pixel dimensions for your study.
3. explained the cos and pros of using Grid and Slope mapping units
4. software and computer specification to run the code easily
5. the main tools for each mapping unit group
6. how to create edit and run a tool in QGIS using the modeler
7. ran the two group step by step using real data
8. convert the output into excel file to make it easier to extract to any modeling software.
9. The expected technical errors and how to avoid it.

23. Outcomes: At the end of this course
At the end of this course, you will:
1. Well understand the different mapping units in susceptibility mapping
2. Learn how to easily choose the wright and appropriate pixel dimension for your map
3. Easily generate
4. Easily able to create your own modeler tool in QGIS environment
5. Automatically generate free-landslide areas for Grid units
6. Automatically generate training data using Grid unit
7. Automatically Generate slope units for entire study area using free DEM (Digital
elevation model ) only

24. Thank you!
To download the QGIS tools and watch the entire course entitled:
A u t o m a t i c D e l i n e a t i o n o f G r i d u n i t s a n d G e o - M o r p h o l o g i c a l
S l o p e U n i t s f o r S u s c e p t i b i l i t y M a p p i n g A n a l y s i s
Visit:
Free preview:
https://goo.gl/Yuxz4P
Full course:
www.udemy.com/user/omar-f-althuwaynee/ Omar F. AlThuwaynee |
Dr. Eng. GIS & Geomatics Engineering
For any inquiries, write to me: scadac@outlook.com

25. • Calvello, M., et al. (2013). "Landslide zoning over large areas from a sample inventory by means of scale-dependent terrain units."
Geomorphology 182: 33-48.
• Gómez H, Kavzoglu T (2005) Assessment of shallow landslide susceptibility using artificial neural networks in Jabonosa River Basin,
Venezuela Eng Geol 78:11-27
• Websites
• https://docs.qgis.org/2.8/en/docs/training_manual/processing/hydro.html
• http://www.ce.utexas.edu/prof/maidment/giswr2012/Ex4/Ex42012.pdf
• https://grass.osgeo.org/grass75/manuals/r.watershed.html
• http://gracilis.carleton.ca/CUOSGwiki/index.php/Exploring_the_Hydrological_Tools_in_QGIS
• https://docs.qgis.org/2.8/en/docs/training_manual/processing/hydro.html
STEPS: Reference

26. Thank you and Happy Learning!
F o r a n y i n q u i r i e s , w r i t e t o m e i n Q & A s e c t i o n , o r
E m a i l m e : s c a d a c @ o u t l o o k . c o m
Omar F. AlThuwaynee, PhD
GIS & Geomatics Engineering