As coin has two sides this problem too has 2 shades.
i'm giving only hints with those form ur debate
1. increase in slum areas
2. due to increase in population city expands. this increases budget resulting economic decline
4. no proper housing due to increase in population
6. transport shortage
7 shortage of water
8. sewerage problems
9. waste disposal (there will be no place)
10.increase of crimes to earn bread and butter
expand these causes one by one with examples. u'll get enough debate.