Second: Floods:
As a result of the accumulation of rainwater in large quantities, the floods are caused by the small valleys of high places. These valleys pour their water into the main valley, whose water collects through its main opening in low places, sea, lakes or rivers. .
The destructive effects of the floods depend on:
- The amount of water discharged from the mouth of the valley.
- The speed of discharged water.
- The size and quality of portable rock gelides with water.
We find that Egypt is among the countries threatened by the danger of flooding, especially in the province of Sohag, especially low areas, which are all in danger of the flood.
The eastern plateau of the Nile Valley is more dangerous than the western plateau. And to determine whether the floods constitute a destructive threat or not due to several factors, including:
1 - climatic conditions that affect the amount and severity of rainfall.
2. Soil characteristics that may allow water to pass into sub-surface layers.
3 - Agriculture and grasses that impede the movement of water.
4. The natural characteristics of the wadis forming the surface drainage basin, such as shape, length, depth, breadth, slope, wadding of the valleys and the height of drainage basins.
5. Rocky and geological characteristics of Earth layers.
Can we control even minimal risk of flooding?
Of course, everything has a way out or a solution, even if it is simple, and the consequences of this disaster are:
1 - Rise buildings in low areas so as not to be affected by floods caused by floods.
2 - The construction of water parks and banks around the agricultural land and buildings and buildings.
3 - Conversion of the Valley of the valley to the nearest canal or bank.
4 - The construction of dams in the areas of valleys, characterized by high water rush before the confluence of sub-valleys in the main valley.
This leads us to engage in deeper scientific means that increase the safety of the human being and reduce the chances of being exposed to the anxiety and panic caused by the exposure to disasters that have no income even if the cause of some of them, but does not want to go into the consequences.
Remote sensing and its environmental applications
(Electromagnetic Spectrum):
We can also call it another name (Aerial Images) The history of remote sensing or aerial imagery dates back to 1858 and is used for military and civilian purposes.
Definition:
is the use of electromagnetic spectrum through a set of devices to collect information about a particular purpose remotely and without approaching this purpose and is processed this information in several patterns, such as magnetic strips or in the form of color or non-colored images used in our various environmental fields such as: Agriculture Geography, geology, engineering, forestry and environmental pollution, and is important in avoiding environmental risks and disasters.
The sense of electromagnetic energy is done in two ways:
1 - devices (sense) or sensor photographic or photographic.
2. Sensor (s) or electronic sensor.
Sensation or photographic or photographic sensor is a chemical reaction on the surface of a sensitive film to record differences in energy on the resulting image.
The sensors or electronic sensors generate electrical pulses that correspond to the difference in reflected energy.
These pulses are recorded on magnetic strips. These pulses can be converted to images on the television screen and can be photographed with specific films.
In the case of thermodynamics on films of these films, And not (Thermal Photograph) because the film is not a means of sensing thermal energy. As for the automatic sensors of the color satellite images do not reflect the real colors that were photographed, so they are pictures called false colors.
The following purposes are shown in the colors that we will mention in the table:
the purpose
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the color
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- Weeds
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- Red
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- water
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- Dark Blue
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- Suspended sediments
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- White to light blue
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- Red layers
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- Yellow
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- The barren soil
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- Blue
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|
- White to yellow
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- the cities
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- Blue
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- Cloud and snow
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- White
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The electromagnetic spectrum is divided into several parts or ranges, each with a certain range of wavelength, and the visible part of the electromagnetic energy is small. Its length is between 0.4 - 0.7 micrometers and is divided into three colors of different wavelengths: a.
The blue color is 0.4 - 0.5 micrometer.
Green color of 0.5 - 0.6 micrometer.
C) Red color of 0.6 - 0.7 micrometer.
At the beginning of the blue (visible part) UV rays and at the end of the red color of the visible part also lies the infrared waves and divided into:
1 - waves close to the infrared.
2. Medium infrared waves.
3. Thermal infrared waves.
When electromagnetic radiation falls on Earth, part of it is absorbed and another part is executed and another part is reflected.
The ratio between these three waves varies according to the nature of the earth. Remote sensing depends on the wavelength band where the reflection is prevailing, provided that this reflection of energy is accompanied by its diffusion, because the diffuse reflections contain information about the color of the reflector surface, and those that are not accompanied by propagation do not contain such information.
This leads us to one fact That remote sensing takes care to measure the properties of diffuse reflections of terrestrial phenomena.
It has been observed that the objects with higher temperatures emit continuous thermal and electromagnetic radiation with a wide range of wavelengths.
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