Dam-break Study using HEC-RAS

Well, actually I am looking for a dam-break study which show the simulation of the dam during breaches. Unfortunately, I only see simulation with high flow in many online website and youtube. That's not a dam-break simulation.

First, there shall be a description on how to simulate the dam-break using HEC-RAS. What are limitations of software and simplified assumption. Let's talk about a real case of dam-break. Dam-break could happen due to failure of its embankment structure either due to overspilling or piping. For low-dam structure, overspilling is possible as it was not designed in high safe level. For high dams, piping failure is more common occurred. 

After, we have decided what kind of failure that we will simulate, the next step is to build dam breach size and time. How big the dam breach and when it progress until it totally breaches. An example of dam breach parameters and time progress to breach can be seen below:

https://www.hec.usace.army.mil/software/hec-ras/Ok, remember in any dam, it always any spillway structure for emergency. It means when flood occurs the high flow will go to spillway structure. So, you need to model spillway structure as a weir and breach parameters along the embankment. 

The example above is sine wave progression of breach. Normally the breach progresses constantly until it reaches maximum and start to breach total. That's why in many cases, it was simulated in sine wave progression. Of course, you are free to choose linear progression.

Once you have done with the breach parameters setup, it is important to set the geometry of the dam and 2D flow area. It can be set as 2D connection between storage and 2D area. In the example below, I set 2D connection within 2D flow area. It means the simulation will be in totally 2D. If you use connection from storage to 2D flow area, it will simulate the storage first which I don't really interest on it. So, remember to take the inflow directly from the outlet of the dam. 

You may have error messages when you started to run. In my case, the error is : "has a weir elevation lower than the cells they are connected to". The error is obvious that your weir levels some are lower than the 2D elevation levels. What you need to do is change the weir elevation higher. Make sure all are higher. As my original weir levels were determined from terrain levels, there will be slightly different due to interpolation and cell size matter. The easiest way is just copy the weir levels and add with roundup formula in excel. 

If no error messages again, you can see that the model is running again. Wait until it finishes run and check the results. Make sure that everything is make sense and as what you wish for.

The last but not least is to check the results. This is the tricky part. You have at least understand the concept of hydraulic. Imagine how much flow it is and where it flows and whether the process from low to high to breaching time all are make sense. 

If you are just focusing on maximum values, it could be enough. But I like the process where the starting point, the progress and final flood maps shall be acceptable. In some cases, you may need to refine your 2D meshing area and cell size. 

  

Ancillary Structures of Reservoirs

In reservoirs, there are structures that used to support the operational such as spillway, gates, embankment and pumping system. In this post, I would like to explain about spillway structure. Spillway is a structure that used to divert the flow during extreme events. When flood occurs, the water level will rise higher than normal time. This must be anticipated by providing a spillway structure. The spillway structure will bring all the overflow water to the downstream area. Besides to protect the embankment from flood flow, the spillway will also minimise the flooding at the downstream area. 

One of types of spillway is Ogee spillway. The shape just likes triangle. It was designed as certain flood level. If flood level higher than crest level of the spillway, it start overspill. The example of oree spillway is shown in figure below.

The video of the ogee spillway: Apa itu Spillway? - YouTube

Do you believe in Climate Change?

There are some questions out there regarding is that climate change is true? well, recently I worked for a project that forced me to look at various data including long-term rainfall and temperature data. This is rainfall data in Australia. If we compared the long records with current rainfall data, surprisingly, the four months cumulative rainfall has more than any annul record from 1859 to 2021. 

I also looked at the climate data from Singapore, the temperature has rise significantly. If looked at long-term trend, we can conclude that temperature is getting higher.

In term of rainfall, it is going up and down as a normal pattern. But if look at the average rainfall, we can see that it is going up. 

You may believe or not, but this a real data that tell you something happening in our climate. Another question is do we need do something or no need as it may just a climate change. 

Data Analysis

When you work with hydrological data, it is always good to screen and assess the quality of data. These kind of questions must be answered such as how many years of available records? and missing data. Rainfall data will useful if it is no missing data. The missing data will cause the values are less which subsequently cause the rainfall accumulation is less.  One of software that I commonly used is HEC-DSSVue. 

Besides, for visualization purposes, this software can be used to manipulate data using math function and for database input that will be used in HEC-HMS or HECRAS (see example of rainfall data below).

ProjectLibre

 It is always interesting to learn something new. A few days ago, I have learned ProjectLibre and I think this is cool that every project engineer/manager must learn about it. If you have familiarized with  Microsoft Project, then this software is exactly the same. The best one is that this software is free. 

You know whatever project is running, you need to monitor the progress and before that, you need to have a plan internally or you need to share with you client. This software can help to do it.  As an example, see Figure below showing the ProjectLibre for a simple kitchen and bathroom renovation project.

Beside for planning and update the progress, this software is also capable to manage manpower and budgetary. You can assign manpower as you wish and control the budget. 

Working as Water Engineer in Malaysia

I write this article when I am in airport leaving Malaysia after 5 years working as water engineer in Malaysia.

For the last 5 years I worked with 2 consultancy firms. Here what I learned and experineced during my stay. 

1. Style

Different company has different style of working. In general, the team has been squezzed from time to time. In some projects, I worked as one-man-show person. The system is not strong. It depends on person-in-charge and the boss who are handling it. It is good and bad actually. The young engineers can learn a lot from many fields and prespectives. But it could give more burden to senior engineers. 

2. Salary

This is sensitive but most of people may aware that engineers not paid well. Malaysia has a program called Protegé to hire fresh graduates with low paid to expose with engineering field. My first impression is that the young engineers won't work hard due less paid. 

Whatever the condition, give a proper salary to the young engineers will motivate them to working hard. It will benefit companies and fasten the transfer of knowledge. In general the salary for fresh graduates is about RM3,000 but I think it must be noted clearly that it is take home pay. It means the costs related to work requirements must be covered by the companies.

For senior levels, it is between RM 5,000 to 10,000. The program to retain thr senior levels must be clear. However, I see in some companies were not well defined. When you are in senior levels, usually you don't want to jump to other companies unless it is really necessary. The flow chart for senior levels must be clear. 5-yrs experience will be endorsed as senior engineers. 8-yrs experience will become accociate. 10-yrs experience will become director. Or it could be other ideas like share holding persentages. This kind of thing must be stated clearly.

3. Working time

It is a standard that the working hour is 8 hrs a day. However, as engineers there are a lot of thing to do that make you overtime. Some companies, they compensate with cash and other with leave. I don't think it is not a wise decision to give leave for overtime. Because the other day, you have to do other works. The best option is still with cash.