Yuanshantz flood diversion engineering (as shown in Figure 1) is a part of the overall improvement project for Keelung River. The Yuansantz flood diversion tunnel can divert 1,310 cms from upper Keelung River with 200-year return period flood 1,620 cms (i.e. 81% flood is diverted into the sea, diveted discharge as shown in Table 1).
Figure.1 Plan view of Yuanshantz flood diversion engineering
Table 1 Comparision of design and experimental diversion discharge
| item |
flood return period
(peak discharge) |
Q200
(1,620) |
Q100
(1,502) |
Q50
(1,375) |
Q20
(1,186) |
Q10
(1,022) |
Q5
(837) |
| design value |
designed river discharge |
310 |
302 |
292 |
277 |
254 |
244 |
| designed tunnel diverted discharge |
1,310 |
1,200 |
1,083 |
909 |
768 |
593 |
| experimental results |
river discharge |
306 |
305 |
304 |
299 |
302 |
284 |
| tunel diverted discharge |
1,314 |
1,197 |
1,071 |
887 |
720 |
550 |
The diverted flood discharge into the East China Sea and the flow condition in the tunnel is designed as gravity flow. The inlet structure, tunnel, and outlect hydraulics is quite complicated and hard to be simulated by numerical model. In order to confirm the design the performance of the engineering design, the physical model experiments were done before construction(as shown in Figure 2~Figure 5). The experimental results were also supplied for engineering design.
(a) 1/50 model
(b) 1/100 model
Figure.2 Model Photo
Figure.3 Experts Visiting
(a) flow pattern in the tunnel
(b) flow pattern in the intlet
(c) flow pattern around flow-directing pier.
Figure.4 Flow Pattern Under Q200
(a)inlet structure
(b)outlet structure
Figure.5 Model Photo