Floods on A9 Highway around Akurana- Fact and Fiction

20 November 2024 12:05 am Views - 2480

There is a lack of transparency and engagement of  concerned experts, advocates, and others. There are shortfalls in  following regulations by officials. Monitoring and enforcement of  regulations by officials are poor

For the past two decades, the Pinga Oya has overflown onto  the Kandy-Jaffna A9 highway along Akurana and adjacent towns. After two  major floods in 2022 and 2023 which overtopped the A9 road by 11 feet,  the 2024 flood season has already commenced on the 8 th of November 2024  with a flood that reached 5 feet.  

The Engineers’ Association, Akurana (EAA) has been deeply  concerned about the repeated flash flooding of Akurana from the Pinga  Oya tributaries. Here we set out the position of our scientists and  engineers who are deeply engaged on the causes of these flash floods so  as to address some misinformation that stands in the way of an effective  response.  

The primary causes of flooding are:  

 

• The continued construction into the river and its margins.  
• The filling of flood overflow zones.  
• Land cover used for soil and vegetation  beneficial in the infiltration of water to the ground is being reduced  rapidly in the catchment.  
• Dumping of solid waste and construction debris in the river.  

The Polgolla Reservoir Does Not Cause the Flash Floods.  

Some attribute the flood in Akurana as due to the impact of  the Polgolla barrage. No one has provided any scientific evidence to  support this claim. Instead, proponents recount anecdotes which they  interpret as causal rather than coincidental. The arguments as to why Polgolla could play a minor role are -  

The top barrage gates of Polgolla are about 10 meters below  the road level of Akurana. Thus, closing the gates cannot cause  backfilling of water. If the Polgolla barrage caused backfilling, then  the Katugastota and Ambatenna areas and areas at lower elevations like  Akurana should also be flooding. This is not the case!

 

Some attribute the flood in Akurana as due  to the impact of the Polgolla barrage. No one has provided any  scientific evidence to support this claim. Instead, proponents recount  anecdotes which they interpret as causal rather than coincidental  

In all flash flooding events, water in the river in Akurana  flows rapidly towards Katugastota.There was no flood reported in the  first 10 years after the barrage was constructed in the 1980s and very  few floods were recorded in the 1990s.Some argue that the silt has built  up in the reservoir leading silt upstream. There would be an impact due  to silt accumulation, however the dominant presence of construction  debris, mud and household waste accumulation on the riverbed has not  been addressed.  

Some speculate that Climate Change may be a cause. There is  no evidence for that based on rainfall records. Rainfall intensity has  not increased in the last two decades.  

Why have the Floods not been Mitigated? 

Effective flood mitigation policies are unfortunately held  back due to misinformation, misdirection, neglect of science and  engineering, and even a lack of common sense. At present,  

The public are unable to contribute to the governance of the river and its catchment.  

There is a lack of transparency and engagement of concerned  experts, advocates, and others. There are shortfalls in following  regulations by officials. Monitoring and enforcement of regulations by  officials are poor.  
 Rigorous engineering and scientific analysis do not inform remedies and policies.  

Recently Proposed Mitigation Steps

Here we set out some on the mitigation steps for developing  effective flood mitigation and river restoration. After the major  floods of December 2022, the mitigation steps announced by the  government officials led by the District Secretary were -   

1. To remove silt from the riverbed.  
2. To remove some structures on the river.  
Widen the narrow (Mangos watte) bridge near the Akurana sign board at the 9th km post.  
Widen the bridge going to Neeralla near the 10th km post.  
3. Setting up an alert system for the Polgolla barrage to open its barrage gates at the time of flooding in Akurana. Of these,  

The river silting has been carried out in a few flooded areas in early 2023.  

The central span of the Mangos Watte Bridge has been broken.  

However, even with these mitigation steps, the flood levels  were higher in November 2023 with a daily rainfall of 120mm compared to  December 2022 even though the daily rainfall was only 70mm.  

Further, various other construction and earth dumping in  the river and its margins and catchment have enhanced the causes of  flooding. Excavating the river alone does not help except for a few  months until the next flood.  

EAA Recommends the Following Principles for Flood Mitigation  

Transparency and Public Engagement  

1. Information about the governance of the river, its  margins, and its basin should be widely available, particularly to  women, youth, and concerned persons, such as engineers, scientists, and  advocates.  Fix Shortcomings in Governance Problems  
2. Better informed governance of the Pinga Oya and its catchment is the prime need.  
3. Rules and Regulations about river and catchment need to be enforced.  
4. Government officials, engineers, scientists, and land use planners should be transparent.  
5. Sound Technical Plans and Transparent Implementations.  
6. Sound Engineering and Science should inform the analysis.  
7. Engineers and Scientists from the area should be involved.  
8. Bold Long-Term regional planning priority in needed.  
9. Holistic River Management considering people, pollution, and the environment  
10. Restore and prioritize public access to the river, for washing, bathing, and recreation.  
11. Prevent and reduce pollution and dumping.  
12. Protect fauna and flora to support ecosystem health  

The writer is the Secretary, Engineers Association of  Akurana, Convenor, Restore Pinga Oya and Principal Scientist /  Engineer, Federation for Environment, Climate and Technology, Digana,  Akurana, Maldives and New York (www.fect.lk and www.disaster.lk and  www.climate.lk). He also served as the Former Senior Research Scientist,  Columbia University Water Center and International Research Institute  for Climate and Society (which has been hosted after starting an R&D  program 20 years ago with the Mahaweli Authority of Sri Lanka).