Zhoukou River is the main river which flows through Kaohsiung, Maolin District. It's a major tributary for the Gaoping River. The smaller rivers flowing into Zhoukou are home to numerous waterfalls, but the main river is mostly flat and smooth below Douna Village. The farthest publicly accessible road is at Hongcheng Xiagu, making the bottom 15KM of the river accessible for Kayaking. This can be broken up into three ~5KM sections, which take 1-2 hours each, depending on the water levels and type of boat you are using. There are not difficult rapids in the lower prat of the river, but the river does make many sharp turns.
Part I: Hongcheng Canyon to Laoying Valley, 4.5KM
Thi section is quite and beautiful. There is no road access along the way, and no man-made structures. The route ends after Douna Suspension Bridge. Under the white bridge there are remains of temporary bridges. These can leave metal objects in the water. It's advised that this section is skipped, and if continuing, to carry your craft to Dragon's Head Mountain and put in there.
Part II: Dragons Head Mountain to Wanshan Village, 5.3KM
This section takes the long way around Snake's Head Mountain. There is a short Class III rapid at the nose of Snakes Head Mountain. After 4KM, a tributary from the left side leads to Passion Valley Waterfall. A little over 1KM latter you will arrive at Wanshan Memorial Park. There is a crumbling concrete barrier on the right side. It's recommended to float past it and dock after passing the construction, or continuing on another 100m to the next road access.
Part III: Wanshan Village to Lover's Gorge Waterfall: 4.7KM
The last section of the river is relatively straight compared to the previous one. There are a few sections with large rocks and also some minor construction works around the bridges. There is road access at the bridge to Maolin Valley Waterfall, after 2.3KM, and also at the bridge to Lover's Gorge Waterfall, after 4.7KM. If you wish to continue all the way to the entrance of Maolin, it's a nother 2.5KM, but the river may dry up at the water station inlet, 100 meters from the end.
For general information about boating and safety, please read this article.