2011/7 Umyeonsan Mt. Debris flow problem Prof. Ko-Fei Liu National Taiwan University
The Interim Report1. Is a very good report regarding potential hazard and related assessment. Or the best I have ever seen.2. But discussion on individual site can not only rely on statistic data analysis which is correct to use for a larger number of sites.3. Regarding the issues that needs resolved, this report is not prepared for it.4. Dispute resolving equals lawsuit and needs evidence or some kind of proof of the crime.
Adequacy of recovery works done for the slopes failed in 20101. Not considering ground water issue, and not enough protection for rain fall, it is indeed mot adequacy. I do agree with the report.2. But a more detailed description for 2010 emergency countermeasure design is necessary. So that there is enough evidence to identify the responsibility of design or construction.
Effect of landslide and drained water from Air Force base Water seeps in Soil Military base wall Concrete and without drainage system
Military base wallConcrete and without drainage system
To identify the responsibility of air force base,we need information on1. Drainage system design on 2011/72. If there is still construction work which requires vibration or penatration3. The new drainage system which put water in downstream channel is a lot safer and a huge improvement.
How much rainfall? The probability of occurrence is too high alone boundary
Water level high, Top soil depth is thinSo land slides and debris flow should startfrom mid stream
Ecological reservoirTo identify the role of ecological reservoir, it is essentialto know what is flow out of the ecological reservoir.1. If only mud flow flows out of the reservoir, then the reservoir has succeeded in storing all the sediments and therefore reduced the disaster. There is no description of the situation right after the disaster. Is it a lot of debris hit and deposited in the downstream, or just mud flow came down and flood most of the people. This has to be ensured through photos or interviews with local people.
There in not much ofbig boulders ordebris, so it could bemud flow. Thenreservoir is good
To upstream原游泳池所在地點 破壞點
There was anatural dam ashigh as 20m
Source is from air force base
1. If it was debris flow came out of the damaged spillway, then a simulation of debris flows is necessary. Since the main stream from spillway to 500m upstream, it is very flat with less than 10 degree, so if debris flow came as one single large wave, this reservoir should play a role of reducing the disaster. However, if debris flows came as many small waves, this reservoir may have collected all the sediment and created a huge debris flow and make more damage to downstream.2. A careful numerical simulation can solve this question
Further improvementThere will be debris flow and landslidesin the future in this watershed.A regular inspection plan andmitigation might be needed
Blast from tunnels1. Logically, places near the blast should be influenced moreseverely. So if blast indeed has its effect on soil and bedrocks,then the portion just above the tunnel can be a best proof.Since there is no evidence of landslides or debris just above thetunnel or in the surrounding area, this is a proof that blasts hadlittle or no effect of initiation of land slides or debris flows2. Does the blasts weaken the soil and bedrocks such that debrisflow came from upstream? There is no trace of erosion near theblast.3. Soil actual can absorb energy from blasts, so there should beno effect from the blasts for 2011/7 debris flow.4. Will there be any long term effect if bedrocks are cracked,remains to be seen