To Whom It May Concern
This blog consists of the following categories:-
a) Formation of river landforms with photographs of actual locations of river features found in the world.
b) The process of constructing physical models (shown in photos and videos) of river features.
c) Our group members' roles and duties.
For the navigations to access these, please click on the names of the various river features to your left.
Acknowledgements:
1. Rivers & Floodplains from the National Library.
2. Mgill's survey of Science, Earth Science Series, Volume 4 from the National Library.
3. Pictures' sources are from the internet.
Regards
Extremeflow
Waterfall
A waterfall is a permanent flow of water over the edge of an erosion-resistant cliff.
The formation of Waterfalls
1.Waterfalls are found in the
upper course of a river. They usually occur where a band of hard rock lies next to soft rock. They often start as rapids.
2. As the river passes over hard rock, soft rock below is eroded faster than the hard rock, leaving the hard rock elevated above the stream bed.
3. The 'step' in the river bed continues to develop as the river flows over the hard rock step (
Cap Rock) as a vertical drop.
4. The drop gets steeper as the river erodes the soft rock beneath by processes such as
abrasion and
hydraulic action. A
plunge pool forms at the base of the waterfall.
5. This
erosion gradually undercuts the hard rock and the plunge pool gets bigger due to further hydraulic action and abrasion.Eventually the hard cap rock is unsupported and collapses. The rocks that fall into the plunge pool will continue to enlarge it by abrasion as they are swirled around. A steep sided valley known as a
gorge is left behind and as the process continues the waterfall gradually
retreats upstream.
Floodplains
Floodplains historically have been the locations of dense human population, providing fertile land and water that enabled early human settlements to attain
some degree of performance. They have also been the locations for recurring damage from floods.
Floodplains are well named. They are some of the most level surfaces on Earth and they are known for
frequent floods. They also are probably the most agriculturally productive lands on Earth. The earliest concentrations of civilization are associated with the floodplains of historical rivers whose names are well known:
the Nile, Ganges, Euphrates, Yangtze, and Huang. These floodplains are still among the most populous areas on Earth.
A floodplain is a landform, a physical feature that is studied in the discipline of geomorphology. Its origin is linked with frequently recurring floods. One of the most studied floodplains is that of the
Mississippi River. Floods on the lower Mississippi Valley today are to a large degree under human control; at least the floodwaters are restricted to certain areas where they will do the least damage.
In order to understand the floodplain, it is necessary to understand the processes that brought it into being. The originating river did not always possess the floodplain, and many rivers today do not have floodplains. Imagine the stream in the figure as it might have been perhaps millions of years ago. The stream was possibly flowing in a narrow channel with high land along either side. There was no level land adjacent to the stream—no floodplain;
its formation would require eons of time of erosion and deposition. As the stream eroded, its channel deepened and also attempted to erode laterally, but the vertical down cutting was dominant and the lateral cutting ineffective.
During a flood, the discharge exceeds the channel capacity, and the excess overflows onto the level adjacent land. The term “floodplain” is now appropriate.
Floodplain of Mississippi River
Floodplain of the Nile
Floodplain of Ganges
Floodplain of Euphrates
Delta
A delta is a mound of sediment deposited where a river channel enters a body of water (such as a lake or sea) and supplies more sediment than can be carried away by currents in the water body.
At the river mouth, the previously confined flow expands and decelerates, depositing its
sediment load. The coarse bed load is deposited close to the mouth (as a mouth bar), whereas the finer sediment in suspension is carried further into the water body before being deposited. Current in the body of water (perhaps associated with tides, wind waves, geotropic flows, or turbidity currents) may subsequently rework and move the deposited sediment.
Localised, long-term deposition of large amounts of sediment associated with the major rivers of the world normally leads to subsidence of the depositional region. Thick and extensive deltaic deposits commonly contain important
reserves of oil, gas, and coal.
The factors controlling the different stages of delta formation, hence delta geometry and facieses, are:
(i) the supply rate and size characteristics of sediment delivered by the river
(ii) the relative density of the river water and the receiving water
(iii) the nature of the currents in the receiving water body
(iv) the nature of subsidence and eustatic sea-level change, affecting relative change in base level.
There are two types of Deltas: Delta
plains and Delta
fronts.
Mississippi Delta
Irrawaddy Delta
Members
Group name: Extremeflow
Chai Bin Bin (1)
in charge of
-Design and creation of personalised blog
-Constuction of floodplains
Chan Ker Ling Vivian (2)
in charge of
-Search for photographs of actual locations of river features
-Construction of waterfall
Tan Qiu Ying (12)
in charge of
-Research on river landforms in the National Library
-Construction of delta
Lee Meng Wei (24)
in charge of
-Research on river landforms in the National Library
-Construction of river and trees
Liu Shan Yi (29)
in charge of
-Compilation of research
-Construction of waterfall
END#
