Waterfalls and it's Types

A waterfall may be defined as a vertical drop of water of enormous volume from a great height in the long profiles of the river. Waterfalls also occur where melt water drops over the edge of a tabular iceberg or ice shelf.

       Waterfalls are commonly formed in the upper course of a river in steep mountains. Because of their landscape position, many waterfalls occur over bedrock fed by little contributing area, so they are ephemeral and only occur during rainstorms.

Waterfalls or falls are caused because of sudden descents or abrupt breaks in the longitudinal course of  the rivers due to a host of factors e.g  variation in the relative resistance of rocks, relative difference in topographic reliefs, fall in the sea level and relative rejuvenation, earth movements etc.

       A fall line is the imaginary line along which parallel rivers plunge as they flow from uplands to lowlands. Many waterfalls in an area help geologists and hydrologists determine a region's fall line and underlying rock structure.

Types of waterfalls:

      There are many types of waterfall which leads to debate over classification. The waterfalls vary so greatly in terms of their height, shape and size, dimension and volume of water that it becomes to difficult to classify them in certain categories.

Waterfalls are categorized in two types on the basis of mode of their origin . 

1.     Normal waterfalls

2.     Minor waterfalls

1    Normal Waterfalls: Normal waterfalls include those waterfalls which are formed due to variation in the resistance of rocks. These waterfalls are indicative of youthful stage of steam development and ungraded long profiles of the streams.water falls include the falls which are originated due to interruptionin the cycle of erosioncaused by rejuvenation.

a)     Steep falls

b)     Caprock falls

c)     Barrier falls

d)     Plateau falls

a)    Step Falls:

       The arrangement of alternate bands of horizontal beds of hard and soft rocks in the course of the rivers produces a series of low water falls due to differential erosion. These falls are in fact rapids. Bhagawati falls on the Krishna River in the Raichur district of Karnataka (India) is an example of step (cascade) falls.

b)     Caprock Falls :

     The caprock waterfall is dolomitic limestone which is succeeded below by the successive beds of shales, limestone, sandstones, and sandstones interrelated with shales. This type of fall is supposed to have been formed about 10,000 years ago.it is receding at the rate of 3 to 4 feet per year.the caprock is of resistant conglomerate. The example of caprock fall is Kaieteur , British Guiana.

c)  Barrier Falls: 

         Sometimes alternative resistant and soft rocks are arranged in structure of the earth in vertical manner . In that area  soft rocks are eroded away rapidly and  the resistant rock beds are less eroded and hence from precipitous scraps in the course of the river which give birth to waterfalls of steep slope . This falls is called Barrier falls.

 

d) Plateau waterfalls:

       The rivers coming from over the plateau surface form waterfalls when they descend through the precipitous escarpments of the plateau and enter the region of significantly lower height. The Congo River has formed 275 m high Livingstone Falls while descending through the Afri­can Plateau.

Similarly, the Orange River has formed 140 m high Aughrabies Falls at the margin of the plateau. Nearly all of the significant northward drain­ing streams and their tributaries have formed water­falls at the northern margin of the Rewa plateau (M.P.) e.g. Chachai Falls (127 m) on Bihar river, Kevti Falls (98 m) on Mahana river, Odda Falls (145m) on Odda river etc. Karo River has formed 17m high Pheruaghaugh Falls at the southern margin of the Ranchi plteau.

       Such falls are called as scarp falls. Hundru falls (75 m) on Subaranrekha river (near Ranchi), Dasam falls (39.62 m) on Kanchi river (east of Ranchi), Sadni falls (60m) on Sankh river (Ranchi plateau) etc. are the examples of scarp falls or knick line falls. The Tons River while descending through the Rewa plateau and draining northward to meet the Ganga makes a vertical falls of 70m known as Purwa falls. Similarly, its tributary the Bihar River makes a stupendous Chachai falls of 127 m height.

      Yenna falls (180m) on Mahabaleshwar plateau, Gokak falls (54 m) in Belgaun district (Karnataka), Gersoppa falls (253m) on the Sharavati (in North Kanara), Sivasamudram (90m) on the Cauvery river etc. are also examples of scarp falls.

2 Minor Waterfalls

A)   Falls originated due to endogenetic forces:

i)                   Fault falls

ii)                Falls due to upliftment

i)      Fault falls: this waterfalls are formed along the fault scarps which are created due to faulting across the river valleys. Example: Victoria falls on the Zambezi river.

ii)       Waterfalls Due to Upliftment:

        Waterfalls of varying dimensions are formed due to upliftment of local nature in the courses of the rivers. These water­falls are obliterated when the rivers regrade their longitudinal profiles. A series of waterfalls on the rivers along the junction of Palamau upland and the northern flat plain (Palamau district, Jharkhand) are said to have been formed due to origin of escarpment caused by the upliftment of southern Palamau during Tertiary period. Patam falls (45.72 m) and Datam falls (30.45 m) on the Patam River (in Bhandaria Anchal, Palamau, and Bihar) are typical examples of such catego­ries.

     Gersoppa falls (253m) or Jog falls is also believed to have been formed due to upliftment. The waterfalls on the eastern margin of the Ranchi plateau (e.g. Hundru falls on the Subarnarekha river, Dasam falls on the Kanchi river, Jonha or Gautamdhara falls on the Gunga river etc.) are also quoted as the examples of waterfalls resulting from upliftment.

B)   Falls originated due to changes in the level of valley floor:

1)     Due to lowering of valley floor

a)     hanging valley falls

b)     glacial hanging valley falls

c)     falls due to river capture

d)     coastal hanging valley falls

e)     knickpoint falls

Hanging Valley Falls:

Sometimes, waterfalls of varying dimensions arc formed when the tributary streams join their master streams from great height forming hanging valleys (fig. 18.6). In other words, hanging valley falls are formed when the level of the junction of the tributary streams is much higher than the level of the main valley of the master stream.

The Rajroppa falls (10m) at the junction of the Bhera nadi and the receiving Damodar river (located to the north of Ranchi city) is a typical example of hanging valley waterfalls as the Bhera nadi after coming from over the Ranchi plateau hangs above the Damodar river at its confluence with the latter. The Gautamdhara or Jonha falls (25.9m) is another example of this category of falls. In fact, the Gunga River hangs above its master stream, Raru River, (to the east of Ranchi city) and forms the said falls.

Glacial Hanging Valley Falls:

The fluvial origi­nated river valleys are largely modified by glaciers during ice ages. The glaciers flowing through the main valleys deepen them more due to erosion than the tributary valleys. Thus, the tributary valleys hang over the main valleys and discordant levels are formed.

These valleys are again occupied by the rivers after the ice age is over and glaciers are ablated. Consequently, the tributary streams hang over the main rivers at their junctions and waterfalls are formed (fig. 18.6). Such glacial hanging valley waterfalls are found in Norway, Sweden, Finland, Canada etc.

 

Waterfalls Due to River Capture:

     

       Sometimes, waterfalls are formed when the streams flowing over higher but flat lands are captured by the streams of relatively lower height. Thus, the captured streams drain into the captor streams by making waterfalls. Such falls are abundantly found in the Himalayas.

 

Coastal Hanging Valley Falls:

        

Sometimes, waterfalls are formed when the streams flowing over higher but flat lands are captured by the streams of relatively lower height. Thus, the captured streams drain into the captor streams by making waterfalls. Such falls are abundantly found in the Himalayas.

 

Knickpoint Falls:

         The breaks in channel gra­dient caused by rejuvenation (either due to upliftment or fall in sea level) are called knick points or heads of rejuvenation. These breaks in channel gradient or knickpoints denote sudden drops of elevation in the longitudinal profile of the rivers and allow the water to fall down vertically giving birth to waterfalls of vary­ing dimensions.

       Hundru falls (76.67 m) on the Subarnarekha river (near Ranchi city), Jonha or Gautamdhara falls at the confluence of the Raru and the Gunga rivers (to the east of Ranchi), Dasam falls (39.62 m and 15.24 m) on the Kanchi river (east of Ranchi), Burhaghaugh falls (148 m) on the Burha river, a tributary of the North Koel (Palamau upland, Jharkhand), Dhunwadhar falls on the Narmada river (near Jabal pur, M .P.), major fall s of Rewa plateau (e.g. Chachai falls-127 m on the Bihar nadi, Kevti falls-98 m on the Mahana nadi, Tons or Purwa falls-75m on the Tons river, Odda falls -145 m on the odda nadi etc.) etc. are the examples of knick point waterfalls.

2)     Due to obstructions in the river courses 

a)     Falls due to Lava-dammed waterfalls         

b)     Falls due to dams

c)     Falls due to glacial morains

 

a)    Lava –dammed waterfalls:

Sometimes the flow of river water is obstructed due to formation of lava barrier across the valley. This falls are almost permanent.

b)     Lndslide-dammed waterfalls :

This falls is originated when huge volume of debris slides down from the nearby hillslopes into the river. This debris obstructs the free flow of the riverby making barrier across the valleys.

f)      Falls due to glacial morains:

Moraine dammed waterfalls are formed due to damming of river flow by morainic debris. This type of river makes falls while crossing through the morainic ridges formed across the valleys.