8a)
i)Encroachment : More migration lead to
less availability of land which lead to higher economic value of land. 
ii)Pollution: Explosive increase in the urban population without
corresponding expansion of civic facilities such as lack of adequate infrastructure for the disposal of waste results in waste clogging the
natural channels and storm water drains.
iii)Illegal mining activities: Illegal mining
for building material such as sand and quartzite both on the catchment and on the bed of the lake have extremely damaging impact on the water body. 
iv)Interference in drainage system:
Drainage congestion caused by badly
planned construction of bridges , roads , railway tracts, hampers the
flow of water and the result is flood.

8b)
- Flooding leads to loss of human life 
- Flooding leads to damage to property
- It leads to destruction of crops

8c)
i)Improving Drainage
Improving water drainage helps control floods by
facilitating easy flow of excess water, especially in urban areas during flash floods. 
ii)Building Dikes and Levees Dikes and levees are flood-control structures built to fight
river flooding and water surges. 
iii)Building Canals
Canals are artificial water channels that can be crucial to flood prevention. Canals facilitate control of water levels passing through, and form linear reservoirs and water
locks. 
iv)Harvesting Rain Water
Harvesting rainwater involves collecting and storing rainwater and can not only prevent floods, it can also curb urban water scarcity.

 4ai)
i)caves
ii)sinkholes
iii)skyline landscapes
4aii)
Drawing
4b)
i)Limestone are all used to neutralise excess acidity of soil in agriculture practice. 
ii)Limestone is used as a building material. 
iii)It is used in industries to purify iron in blast furnaces. 
iv)It used in Glass making.