Analysis of Flood in Mul District that caused 6 lives and Catastrophic destruction to properties

The flooding of Kuma Creek has caused massive destruction to properties and confirmed six fatalities downstream. Kuma Creek is such a small creek which is  a tributary of Gumanch River which joins with other rivers to form the Wagi River in the Western Highlands Province.

It is unbelievable for such a small creek to cause massive destruction to lives of people and properties downstream. According to preliminary report posted on Facebook dated 4th February 2020 by Stanley Kheel Kewa, it reads: 

"Preliminary reports from Mt Hagen confirm massive scale of destruction by the Kuma river a tributary of the Gumanch river in Mul district of Western Highlands Province. Four adults and five children totaling nine casualties as reported deaths now. More investigations are in progress as surrounding communities are assessing and investigating the magnitude of the destruction.

Local tribes in the area are the Nengka, Munjika & Mele tribes. Locals reporting from Hagen say this is one of the worst natural disasters the community has ever experienced since time immemorial. The Kuma & Gumanch rivers originate from the top peak of the highest mountain range in WHP known as the Mt Hagen range from which the current Hagen city got its name.

The Nengka Kuiprungils, Nengka Oiyambs and Munjika Rapgangils live at the edge of the Hagen range with houses and gardens patched along the Gumanch and Kuma tributaries.

Ken Paul is a local from the area and reports he is in Hagen town trying to mobilize disaster office and news personnel into the area for further investigations and reporting.

This is just a preliminary report with photos of the disaster zone downloaded from fb pages."

Locals on site - photo courtesy of Facebook

Photo Courtesy of The National Newspaper

Debris of flood - Photo courtesy of facebook

MarapanaVillage aftermath - photo by National newspaper

Now,

one would wonder with questions in anticipating superstitions without establishing the facts and without even having a curiosity in mind. The possible cause of the flood can be best explained as follows;

There must be couple of landslips

caused by what is believed to be over saturated water-table/reservoir

contain by permeable rocks

at both steep

sides of the wedge walls/hills

of  Kuma Creek which is indicated on the snapshot below. 

Then the slipped materials must have

formed an embankment or base which blocked the upstream and the water built up at the upper end of the embankment which formed a temporary mini dam. 

As the mini dam rose with altitude, the stress build up also increased until it reached a

bursting failure in which debris of embankment together with other slipped materials along the creek's

pathway were all washed away and flooded the banks of Kuma and Gumanch Rivers which caused the catastrophic destruction to properties and fatality of 6 human lives. 

The mass flow of loose materials which blocked the flowing river which resulted in forming a mini dam were not competent or strong enough to withstand the pressure/stress build up at the upper end of the blockage, it then burst out and flooded the downstream at a greater momentum which is possible for massive destruction.

So sad that  many loved ones lost their lives due to the catastrophic disaster caused by this unusual flood.

Expected failed area

Location Failure is Expected

Marapana Village

Ariel view of Kuma,Tagla Kwip and Marapana

Note  that this analysis is based on opinion only and not substantiated with facts. If someone wants to proof with factual information then someone need to take a walk up the Kuma river and look for any trace of landslip. If that is so then that would be the cause of the flooding. 

To prevent properties and lives, build houses on higher grounds and also build flood walls along the river banks where valuable properties are installed. Do make awareness to kids and matured people to evacuate quick if unexpected signals are given before massive destruction happens again.

Read More

Geothermal System Modelling - Basic Model

Geothermal System Modelling

Report Submitted by Group Fuji

Basic Model

1.0       Introduction

The Basic Model  parameters (basicmodel.in) was used to calculate the transient behaviour of the hydrotherm system up to 100,000 years. Team Fuji analysed the calculation results in the numerical model by changing one of the parameters in the initial model and run the simulation using HYDOTHERM. In this case, the team changed the size of the heat source while keeping the other parameters constant in the model. The calculation results were run at 20000,40000,60000,80000 and 100000 years.

The physical modes of each scenario are demonstrated in the following model diagrams (Fig. 1-5) below. Heat Source is shown at the centre at 4km x 4km x 2km for the basic model which is represented in red cubical color. The size of the heat source is decreased by 3km x 3km x 2km and then increased to 6km x 6km x 2km in that order. Two different input file  with the different  sizes in X and Y direction  (heat source dimensions only) were run using  Jupiter post-processor (Hydrotherm program). After the simulation in the series of years mentioned above, temperature and flow variation were used to explain the trends in cooling rate of the heat source and temperature variation with time, corresponding analysis is illustrated in the discussion section.

Fig. 1 Heat source at the deeper layer
 of the model (2km thick) 

  Fig. 2 Section View of the initial
 model

  

Fig. 3 Overview of the initial block model

  Fig. 4 Section view of the block model when heat source decreased to 3km x 3km

    

Fig. 5 Sectional view of the block model when increasing the
 size of the heat source by 6km x 6km

                               

Note: everything else is kept constant except the size of heat source changed for the next two models.

2.0    Discussion

1.1 Heat source

The trend of the cooling equations (below) illustrate the differences in the thickness of the heat sources. Therefore, the larger the areal extent of the heat source is inverse proportional to the cooling rate.  The bigger the heat source, the longer it takes to for it to cool down.

Figure 6: Cooling rate of the heat source

The cooling equations for the model with 3kmx3kmx2km, 4kmx4kmx2km and 6kmx6kmx2km heat sources are shown below:

respectively.

1.2  Rate of cooling of the reservoir

The graph below portrays the cooling rate of the reservoir, approximately 1km above the heat source where the convective heat transfer currents are mostly upwelling.

4kmx4kmx2km heat source

Figure 7: Cooling rate of the reservoir

The reservoir cooling curves in Fig.7 above have near - similar trend except for the model with 6kmx6kmx2km heat source which has a kink upwelling at 40,000 years.

1.3 Interstitial steam and water flow

1.3.1        3kmx3kmx2km heat source model

At 20,000years, the hot water rises from the center of the model and travels upward towards the surface as interstitial water moves slowly to recharge the reservoir. At 40,000 years, the rising hot water together with the conduction heat transfer heats a larger area above the magma thus expanding the reservoir area (region in which hot water rises upward).  From 60,000 to 100,000 years, the model cools to below 200°C and convective currents carrying hot water upward weakens over time.

Figure 8: Simulation of 3km x 3km x 2km heat source after 20000 years.

1.3.2        6kmx6kmx2km heat source model

At 20,000years, we have two convective upflow regions which may form two reservoirs about 1km on either side of the center of the model (approx. 9000m and 11000m from LHS of the model).

At 40,000yrs, the two reservoirs merge into one as the heat source cools with convective currents weakening as the model ages all the way to 100,000years.

Figure 10: Simulation of 6km x 6km x 2km heat source after 40000 years.

3.0     Conclusion

In this study, only the heat source dimensions were varied without any change in other parameters.  The results were then evaluated and discussed using that assumption.

The areal extent of the heat sources directly influences the convective flow of fluids and temperature. However, transient temperature evaluation indicates that the rate of cooling of the heat source is inversely proportional to the size of the heat source. The larger size (6km x 6km x 2km) of the heat source allows for a longer period of high-temperature fluid convection. 

     

Figure 12 : 3X3 Heat source       Figure 11: 6X6 Heat source

Source: Groupwork Hydrotherm Basic Model Assignment Report -

Contributions to Group Fuji:

Islomove Sunnatullo-Rock Engineering, Koskey Philemon Kiprotich- Geothermics, Gilbert Bett Kipngetich-Geothermics, Gutierrez Donaire Kevin Yamil - Geothermics, Haissama Osmanali - Geothermics, Kuri Las - Rock Engineering, Lim Pagna-Economic Geology, Mwangi Samuel Muraguri -Geothermics, Ngethe John-Energy Resources, Omondi Philip Omollo-Geothermics, Samod Yuossouf Hassan - Economic Geology

Read More