To identify factors affecting landslides, I want to know what data can be extracted using contour map of a certain area. For an example slope of a land can be found. Can factors like geology, hydrology be found using the contour maps too?
contours can give you an insight about the relief of the area (Slope, steepness etc). This helps out to get a general understanding of the watershed source and sinks and flow directions.
In addition to the above, geology in the strict sense cannot be represented with contours, due to the uniqueness of its type (there are a lot of rock types) and uncertainty of its geometry. However, aquifer thickness and/or aquifer layers thickness as well as piezometric surfaces and other features that present a normality in space can be and should be represented with contours. Also, differences and/or percent differences between time steps can also be represented with contours for a variable like monthly rainfall, concentration of a certain solute anion/cation in the aquifer water like Na+, changes in water table level, lake water level, etc.
I hope this helps.
Best regards!
Well,
It depends on available information, you can use data for different spatial (distribution) analyses maps.
Regards
@Dimitrios Voulanas
Thank you for your detailed response. Can't we get geology features such as bedrock structures and unstable bedding sequences using contour maps? And isn't hydrology of an area include different water ways such as rivers etc in that area?
Lasini Liyanage I believe you can get those if you classify them first so you can plot the distribution of those elements but not the elements themselves by using contours
You might take a look at these links and follow through on the references:
https://earthobservatory.nasa.gov/images/89937/a-global-view-of-landslide-susceptibility
https://www.usgs.gov/faqs/what-a-landslide-hazard-map?qt-news_science_products=0#qt-news_science_products
YES CONTOUR MAPS ARE USEFUL TO DELINEATE THE GEOLOGICAL STRUCTURES LIKE FOLDS FAULTS AND OTHER LOCAL STRUCTURES LIKE HEIGHT OF THE ROCK BODY OR ELEVATION OF INDIVIDUAL ROCK THICKNESS / HEIGHT ETC.
Contours give numerical values. Geology is a classification of rocks and cannot be represented using contours. Values like slope, watershed, catchment are all derived from a DEM, which you can generate from a contour map, however I think it would be unlikely that your contour map would be as robust as the NASA SRTM 1 second DEM which should be a publicly available dataset.
Contour lines on a topographic map depict the spot/locations having equal heights. Say contours of 500 and 520 would depict elevations of 500m and 520m on a topographic map of 1:50,000 Scale (1Cm = 500m). Contours are helpful to understand the topography, physiography and geomorphology of a particular area. You can get/ extract information such as relief, elevation, slope inclination, slope direction, topographical features (viz. slope break, topographic break, steepness, plains and many more). Further, you can have an idea about geomorphology, physiography, drainage etc. of a particular area. Geology in a strict sense is not depicted by contours and is mainly related to Geological processes. Nonetheless, while doing geological mapping and geological studies of various kinds, a topographic map in general and contours in particular certainly help a lot. In Digital Elevation Model (DEM) also, contours give very good idea about the area concerned. Contour maps are very much helpful to Geographers, Geologists, Geophysicists, Geomorphologists, Engineers, Planners, Surveyors etc.
Regards
A. Kohli
You can interpolate the contour data and extract
one-. The slopes of the land,
two-. If you know morphometry you can draw the drainage network, according to the spacing of the heights of the contours (10, 20, 50, 100 m for example). And classify drainage basins in many different ways.
3-. You can see tectonic alignments.
4-. It can even suggest land uses according to the slope. Verstappen, 1982 ?.
You can extract spatial informations relating to the slope, elevation, drainage, structural lineaments and watershed from a DEM.
You can get a lot of data out of contour lines and a DEM, but you must use previous knowledge to solve the problem, which arises. And computer program does not do anything alone, you must guide and reach your goal.
You can also extract a curvature and aspect map. The former will help you if your area is concave upward or downward. This might have a little influence if you are planning to model the likelihood of occurrence of landslide in your area. Additionally, you can also derived aspectvmap which tells you to which direction your maximum slope is facing, like north or south. However, it is highly recommended to use the National Elevation Dataset (NED) SRTM DEM as mentioned above. Good Luc!
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