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Logging at Keningau causes flooding at Penampang?

posted Jun 16, 2018, 8:14 AM by jeffery jim


Preamble
Many are eager to share the pretext of Shafie's speech which relates the logging at Keningau and flooding at Penampang. Some are bewildered and some are perplexed with such statement. Not to say the amount of trolling and so on. Previously, i did commented about Warisan's agenda about continuing the construction of SMK Pekan Nabalu which i strongly against since it is too close to fault lines, epicenters and its elevation; and reckon a new lower risk site nearby. Jo-anna Rampas did mentioned this during her campaign and i believe this should be reconsidered with recommendations from earthquake and structure specialist. How about this time, am I going to go against Warisan politicians when it comes to technicality? Let us find out.

1. First of all, before we look into the hydraulic of these two geographical spots; let us look into the division of territory for both districts. Both districts are not adjacent to each other. Tambunan and Papar are in between both districts.

2. Now, let us look at tributaries and river basins around these districts. The main river basins will be the Padas river basin which collect water shedding from Long Pasia and Keningau, then confluence collection at Tenom. Water are then re-route down through Padas river until the Padas Bay and mostly are retained at Beaufort Floodplain. Ranau and the Central of Sabah are divided into two basin systems which is Kinabatangan Basin and Labuk Basin. Papar have its own Papar basin and most of Tuaran district is under the Tuaran Basin. Penampang is part of the second smallest basin which is under the Moyog basin. Again, Keningau and Penampang are not conjoined when it comes to river basin system.

3. Short-term logging licensing shows that only a few of the logging areas in Keningau are close to water bodies or rivers which are part of the Padas basin system. However, there are some areas in Tambunan which are at water shedding area at the border of Padas basin, Tuaran basin and Papar basin.

4. Nevertheless, all that are mentioned above are derived from simplified geographical interpretations where anyone can draw an ideal border for water spatial. In reality, it is more complex than just border of water catchment or shedding areas. Although it is much more convenient for water to travel over areas with best overland flow and very low manning roughness coefficient value.

5. Precipitation dissipates in two conditions; surface runoff and infiltration. What we often have in mind is just surface runoff because this event which relies heavily on IDF curves that usually triggers flash flood or flooding. As mentioned in earlier section, runoff travels in convenient ways; based on spatial. Moreover, such high runoff also contributes to sedimentation and debris. Infiltration usually leads to retention of water until it reaches saturation point where the hydraulic rate began to reduce. At the same time, the saturation point also allow water to accumulate in water bodies; pond, swales, dam and et cetera.

6. How do we connect dots between logging in Keningau and flooding at Penampang? The main culprit to flood in Penampang is the rainfall intensity within this basin. The total annual rainfall at Penampang is the highest in the state with more than 4,000mm while Keningau is less than 2,000mm. It is clear that high water flow and inability to divert or to retain it are the key culprits. There is no direct correlation of event when it comes to topography or worse, it is negatively correlated (water travel from the crest to the sag in laymen term).

7. The indirect plausible correlation of both districts would be the ground water system which do runs through Tambunan connecting both districts. The recharge of groundwater increases when there is less vegetation which increases ground surfaces for infiltration and less retention to exfoliation. We can establish a hypothesis that water from Keningau logging areas do travel and saturates the soil around the Penampang area which reduces the ability for water inflitration (rate) and thus, increases the surface runoff.

8. How drastic does this affect runoff? You need to carryout your own study but I would put it around 10%. By now you should understand that there is a factor that contribute (not lead) to the flooding of Penampang from logging activities in Keningau. I stand corrected if you find anything that is incorrect here. 

For now, I do believe Shafie's speech does contain more essences than some of your trolls.

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