Hi Rayth, thks for updating Sg Rasau. I've been updating rivers in Selangor for the past 1 month, and I hope you won't mind me giving some pointers:

1) Way: Sungai Rasau https://www.openstreetmap.org/way/1282593221 begins correctly until node https://www.openstreetmap.org/node/11902084880 where the waterway should continue south towards Blue Lagoon Waterfall and further to Taman Pertanian University where it joins with the already existing Sg Rasau mapped there https://www.openstreetmap.org/way/878669711 . After node https://www.openstreetmap.org/node/11902084880 it should not be flowing east towards Kinrara Golf Club as rivers don't flow uphill (check against topo lines).

2) Way: Sungai Rasau https://www.openstreetmap.org/way/1282593220 is not Sg Rasau but actually Sg Bohol tributary and very rarely culverts run under buildings. If you look carefully on ESRI, you can actually see the monsoon drain running below the trees in between Petronas and BK5 Hening Park https://www.openstreetmap.org/node/1531129755 . This stream is NOT connected to Sg Rasau but begins from https://www.openstreetmap.org/node/11902084899 

3) As mentioned above, there is no connection between https://www.openstreetmap.org/node/11902084889 and https://www.openstreetmap.org/node/11902084899 . The Sg Rasau tributary begins at https://www.openstreetmap.org/node/11902084889 to flow WEST to join the main trunk at https://www.openstreetmap.org/node/11902084880 

4) Tributary streams https://www.openstreetmap.org/way/1112684894 , https://www.openstreetmap.org/way/1112684893 and https://www.openstreetmap.org/way/1112684888 should not be disconnected from the Sg Rasau main trunk.

5) Where the stream crosses hiking trails ( https://www.openstreetmap.org/node/11902084936 , https://www.openstreetmap.org/way/1112684882 , https://www.openstreetmap.org/node/5156522577 , https://www.openstreetmap.org/node/5104609835 and https://www.openstreetmap.org/node/11902080155 ) you should map whether it is a ford, bridge or culvert. If unsure, place a fixme node where they intersect.

6) Waterways begin as small streams and usually flow for about 2 km before becoming significantly larger. So usually, the first 2 km of the river should be mapped as waterway=stream (can easily be crossed) instead of waterway=river (shoes fully soaked with water when attempting to cross).