(a) List four modes of transportation. (b) Identify four constraints to inland water navigation. (c) In what four ways can the constraints identified in (b)...

(a) Modes of transportation:

1. Road (land) transport.
2. Rail (railway) transport.
3. Water (inland waterway and ocean) transport.
4. Air transport. (Also pipeline transport.)

(b) Constraints to inland water navigation:

1. Waterfalls, rapids and cataracts that interrupt the river and block through-passage of boats.
2. Seasonal variation in water level - rivers become too shallow in the dry season and flood dangerously in the wet season.
3. Silting and sand bars that make channels shallow and difficult to navigate.
4. Presence of vegetation and obstacles (floating weeds such as water hyacinth, sand banks, rocks) blocking the channel.

(c) Ways the constraints can be solved:

1. Construct locks, canals and by-pass channels around waterfalls and rapids to allow boats to pass.
2. Build dams and reservoirs to regulate water levels so that rivers remain navigable throughout the year.
3. Regular dredging of channels to remove silt and sand bars and deepen the waterway.
4. Clear floating weeds and obstacles and mark channels with buoys/beacons for safe navigation.