Consider the following statements regarding the Himalayan Drainage System:
1. The Jhelum river originates near Lake Rakshastal, flows west for a while, then southwest to join the Indus River in Pakistan.
2. The Ganga river is formed by the Bhagirathi and Alaknanda confluence, flows through India and Bangladesh to the Bay of Bengal.
3. The Brahmaputra river starts as the Yarlung Tsangpo in Tibet, flows east, U-turns into Arunachal Pradesh, then Assam and Bangladesh to join the Ganga.
4. Upper Himalayan rivers' erosion mainly forms floodplains and meanders in high altitudes.
Which of the above statements are correct?