Survey finds “shocking” discovery about flooding
Flash flooding in some low-lying areas in Samoa can be attributed to the increase in development over the years.
This was highlighted in a recent survey conducted by SkyEye Samoa with the Ministry of Natural Resources and Environment (M.N.R.E.) and United Nations Development Programme (U.N.D.P.).
The results from the survey will be presented by SkyEye to U.N.D.P. and M.N.R.E. next week.
SkyEye’s Chief Executive Officer, Fa’aso’otauloa Sam Saili, told the Samoa Observer that what they discovered in their survey compared to three years ago is “shocking”.
“There has been a lot of change in terms of development such as human settlement, roads and infrastructure, especially in the upper catchment area,” he said.
“Seeing and analyzing the data collected, SkyEye can now understand why there has been a flashflood just two weeks ago because the water catchment areas are not catching the water anymore. This is because of the human and infrastructure development."
“Pretty much when it rains in the mountains, water just comes straight down. There’s no longer the healthy forest there that usually catches the water and keeps it, so that’s what we understand when that flash flooding happened.”
Fa’aso’otauloa said the need to identify the cause and possible solutions to flash flooding after Tropical Cyclone Gita was paramount.
“After cyclone Gita, there was a lot of flooding and there was a concern for what it’s like in the water catchment areas, especially the upper catchment areas where the water source for Apia urban area is sourced from,” Fa’aso’otauloa said.
“The issue is it is very difficult to actually access these areas because there are mostly no roads there and then there’s also difficulty to view it, to try and get an actual evidence of what the area looks like at the moment, especially after the cyclone.
“So the M.N.R.E. and U.N.D.P. contacted us whether we can survey all these areas so that they can actually get detailed analysis of what’s going on.”
According to Fa’aso’otauloa, M.N.R.E. carried out a similar survey three years ago, which was funded by Australian Aid.
“They wanted to know what is there compared to three years ago, because three years ago, the M.N.R.E. got a grant from Australian Aid and the Australian Aid were able to survey the whole of Samoa using a technology called lidar, which is a very advanced technology for surveying areas,” he said.
“So M.N.R.E. has the information about the topology of Samoa from three years ago, but they want to get an update compared to three years later.
“That’s what we did. M.N.R.E. was kind enough to give us the area that we were surveying in form of lidar so that we can compare the data that we got from our U.A.V. or drones mapping that we did.”
Fa’aso’otauloa said the areas they surveyed included Tiavi, Malololelei, Afulilo Vailima, Papauta all the way to Vaisigano and the area of the mountain included Malololelei, coming down to Moamoa all the way to the ocean.
“The mapping took us more than a month because it is a very big area, very remote area. We surveyed all the area where catchment area of water starts from, so it starts from all the way up the mountain where the water source starts from.
“We surveyed quite a huge area. It’s not just the urban area but it starts all the way from the top down to the coast, so that we have a holistic view of how the whole area is.”
He explained their concern is that when it rains in the upper catchment, the low lying areas are going to flood.
“We believe that’s why the Vaisigano, the Vaimoso River that runs just behind our office gets flooded.
“The outside of our office got flooded, lucky the foundation was high enough, but everywhere else outside was flooded, so we do have a personal stake in it as well.
“That’s why we are pushing this project and making sure that we give every single recommendation and evidence as possible for the decision makers to hopefully make the right decision before trying to reverse how the upper water catchment has been devastated over the past three years.”
Fa’aso’otauloa added M.N.R.E. has a lot of well-developed policies but the issue is getting the evidence to enforce those policies.
“We’ve had preliminary discussions with M.N.R.E. and they’re very excited with the information that we’ve gathered so far.
“We are bringing in some environment experts as well for this project. It is not part of the terms of reference but we believe it’s required because it is one thing to have the data but using it in the best way possible and that’s where the environmental experts come in.
“So people like James Atherton, he’s worked in this area. He has done so many advisements and recommendations in the past years, so he knows this area very well but now we have the data for him and a few other experts to actually prove what they were advising years ago that’s now come to fruition because those are advice weren’t taken into account.”
Fa’aso’otauloa mentioned they’ve recommended a few areas that needs improvement.
“Some of the recommendations that we provided is looking at areas that have been devastated in the past three years to pinpoint those areas for forest rehabilitation, so encourage reforestation.
“In Australia, they have this problem as well, but they have used other methods to try and address it. One of these methodologies is using weeds, planting weed close to the river to try and absorb water. There are specific kinds of weed that grow really fast because if you’re talking about trees, it’ll take years for them to mature, but for weed they can grow within a month. So that’s one of the things we are looking at.
“Also we are looking at areas where it looks like a bottle neck because we were able to identify areas that were like a bottle neck where there are multiple river streams coming together and that area we need to focus on, either do a river flow adjustment or look at ways to try and make sure that when it rains, there’s not a bottle neck there that allows water to keep rising, especially if there are logs there, creating a dam and then it bursts, causing flash flooding.
“M.N.R.E. is doing dredging of certain parts of the river whenever they get funding and we have identified more areas now that needs it periodically.”
Fa’aso’otauloa mentioned the technology they used is called photogramic, so it’s part of the technology that is known as remote sensing. It’s not just about taking photos, the drones and information we get is X, Y and Z coordinates so we can build a 3D map, so that’s one of the things that we are doing with this project.
“We are building are 3D map of the whole area we are capturing so that we can look at it from different angles, so whoever is doing the decision making, they can look at the whole area in 3D model.
“If you are looking at an area from a different angle, it will give you different information. So instead of just one layer, this is a 3D layer version of it.
“The issue that we experienced was the weather, especially when we got to the high mountain area because the clouds were always and issue, so we couldn’t fly. The issue was also accessing certain properties because some people didn’t want their properties to be surveyed and that was unfortunate, so we had to find another way around.
“It took us three weeks to analyse and process the data that we collected because the amount of data we collected from drones we’re looking at terabytes of data. The team, my brother and niece were up almost 24/7 to process and analyse the data because we had a deadline.
“Compared to the lidar data that M.N.R.E. provided, that was also a big hurdle because M.N.R.E.s data had different perimeters than what we did, so we had to adjust both to try and meet.
“The biggest benefit is putting the two data together and you can see clearly what it was three years ago and what it is today. Visually, you can just see what the difference is and the changes.”
Fa’aso’otauloa acknowledges M.N.R.E. and U.N.D.P. for looking at a local company and having the trust in a local company to carry out such advanced project.
“We hope to build this partnership and trust in using local resources.”