What would be the advantages of dividing the class into groups according to the stages of the long profile of a river?

KCSE Geography Paper 1 2006 Section B Question 7.

The diagram below shows river Mandera. Use it to answer question ( a)

(a) (i) Name the process that take place at each of the points marked P and Q. ​

• Point P: deposition
• Point Q:  erosion

(ii) Name the feature formed at the point marked R 

• A cliff / bluff

(iii) Describe how an Ox- bow lake is formed

• An ox – bow lake forms when a river starts to meander on a flood plain
• Lateral erosion  dominates on the outer side of the bend while deposition takes place  on the inner bank
• Lateral  erosion results in the reduction of the rock of land between adjacent bends
• Deposition on the meander  side, especially during floods blocks  off  the  meander
• The river abandons the meander and follows the newly short cut tat was  the neck  of land
• The abandoned meander with its water  forms an ox-bow lake

(b) State five characteristics of a flood plain 

• They have a gently sloping gradient/ flat surface
• They have thick alluvial deposits/ silt/ fertile soils
• They have levees on either side of the river  banks  raised  river  beds
• Some flood  plains  have  marshes/ swamps
• Some flood  plains nave  braided channels
• Some  have deferred tributaries
• Flood  plains have  river bluffs
• They have  meander/ bends  and  some have Ox- bow lakes at their  edges
• Some  have wide river  valleys
• Some  have  deltas/ distributaries

​(c) Explain three causes of river rejuvenation 

• A fall in sea level which increases the velocity of the river, thereby  increasing  the erosive power of the river
• Regional uplift which  creates negative sea level moment  and thus  makes the river to renew  its  erosive  activity.
• Vertical erosion by the river may expose  resistant rock  which creates a knick point thus renewing the rivers erosive power.
• Presence of a lake along the river flow out of the  lake,  its erosive power  increase
• Increase  in river discharge due to increase in precipitation of river  capture  may cause a river to renew its erosive power
• Unequal regional subsidence of land along the river course increases the gradient and therefore the erosive power  of the river.

(d) Your class is required to carry out a field study of a river
(i) What would be the advantages of dividing the class into groups according to the stages of the long profile of a river? 

• The class will be  able to study the entire course  of the river
• It will enable them to obtain detailed  information on each  stage of the river
• It will save on time
• It will enable the study to be carried  out  in an orderly way
• It will encourages participation  of all the members  of the class/ encourage  individual roles
• It will facilitate interaction  among the group members

​(ii) What would be the disadvantage of using secondary data in this kind of a field study? 

• Recorded data could be out of date
• Conditions  under which  such data was collected may be changed
• Obtaining records on the  particular  river was collected  may be  difficult

​Related Geography Searches on external land forms, rivers Form 3 Level

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