(i) They had well covered drains.The drains were covered with slabs or bricks.
(ii) Each drain had a gentle slope so that water could flow.
(iii) Manholes were provided at regular intervals to clear the drains.
(iv) House drains passed below many lanes before finally emptying into the main : drains.
(v) Every house had its own soak pit, which collected all the sediments and allowed only the water to flow into the street drain.

Indus Civilisation is called urban civilisation because
(i) There was well-conceived town planning.
(ii) Astonishing masonry and architecture were found.
(iii) Priority was given for hygiene and public health.
(iv) They used Standardised weights and measures.
(v) They had solid agricultural and artisanal base.

(i) Literary sources
(ii) Aerial photographs
(iii) Magnetic scanner
(iv) RADAR 
(v) Remote sensing methods.

(i) By 1800 BCE, the Harappan culture had started declining.
(ii) It is assumed that the civilization met with
(a) repeated floods
(b) ecological changes
(c) invasions
(d) natural calamity
(e) climatic changes
(f) deforestation
(g) an epidemic might have disturbed the civilization.

(i) A naval dockyard has been discovered in Lothal in Gujarat. It shows the maritime activities of the Indus people.
(ii) Cylindrical seals similar to those found in Persian Gulf and mesopotamia have also been found in the Indus area.
(iii) This shows the trade links between these two areas.