FIJI NEWS

ACTION PLAN

By JOHN ROSS It’s a story that is becoming only too regular. Of course it’s not only Nadi, 2009 and 2012 had the whole West and North in trouble, but
03 Mar 2012 14:41

An aerial view of Nadi Town at the height of the flooding in January this year. photo: Courtesy of nigel Skeggs

By JOHN ROSS

It’s a story that is becoming only too regular.
Of course it’s not only Nadi, 2009 and 2012 had the whole West and North in trouble, but the issue is so complex and the reasons for each area so different that this review focuses on the Nadi basin only.
Every time there is a flood of significant proportions, it directly affects the whole population.
Those in the flooded areas lose property, lives and hope. Those outside lose travel freedom, often income, education is affected and everyone has relations whom they need to help.
In the past 12 years Nadi has had 11 floods of varying intensity.

WHAT HAPPENS
The Fiji economy takes a big hit. A great number of businesses are directly affected, either by flood damage or reduced income because of constricted trading conditions.
Distribution of goods is restricted and production falls because of worker absenteeism.
The country’s balance of payment is adversely impacted because of the need to import to make up for lost primary production in the flooded areas.
There is usually a three-month time lag before the production of farm products regain volume, for some crops the time is considerably longer.
And the impact on the tourism industry is immense, with forward bookings being cancelled and those who are already here being constrained to the resorts. The use of tours and other tourism products are almost non-existent.

WHY NADI?
The flood phenomenon is nothing new for the Nadi basin.
Probably for thousands of years, and certainly in living memory, the flooding has been a part of life in this area.
In the past the floods were a much more regular event, but to some extent the impact has been less since the Drainage Board was formed and started their work in the area.
However, there have been a number of floods where the sheer volume of water was greater than usual and properties were damaged and people died.
In the flood of 1994, the road bridge on the Queens Highway crossing the Nadi River near Namotomoto Village was completely washed away.
The new bridge was built in a different location to achieve a greater height above the river level,

DRAINAGE BOARD
The incidence of flood events decreased some time after the late 1950s and the impact was further minimised by the activity of the Drainage Board in developing a system that had removed all the water lying in the shallow ponds and lakes.
When there was an event, the drained areas filled and had the effect of storing the water without causing damage.
The water then drained into the river after the river level fell.

WEATHER PATTERNS
Weather patterns changed at around the start of the 70s, bringing less concentrated rainfall periods, with the falls spread across greater periods of time.
This had the effect of allowing the waters to drain away before the next significant fall.
This changed weather pattern was also experienced in the East coast of Australia, where there were a series of disastrous flood events between 1950 and 1960 and then the incidence of flooding reduced.
Both Fiji and Australia are now experiencing the sort of weather patterns that existed some 50 years ago.

LOGGING?
A number of people have complained that logging is a contributing factor by increasing erosion levels and speeding up the silting of the river, but there has never been extensive logging activity.
The only attempt at commercial logging in the region was based on pine plantations in the Nausori Highlands and this would have only assisted with erosion control (if indeed erosion was ever an issue).

MEIGUNYAH BEDS
One of the main things that has an impact on the flooding in the Nadi basin is the topography, the shape of the floor of the basin.
Most of it consists of the Meigunyah Beds, a vast area of gravel covering the valley floor and forming a barrier to water soaking to any significant depth.
It is basically flat, with a slight fall to the south west and with variations in places that allow ponds to form.
The beds have a shallow cover of soil, usually formed by decayed vegetation and the residual of soil carried through the floods.
The two main rivers in the valley have cut through the gravel and the river is in most places well below the level of the surrounding land.
A quick look at the river from the Nadi Bridge will show just how deep the river has cut. A significant part of the silting of the river is from the erosion of the banks.

MOUNTAIN VIEW
Prior to the work of the Drainage Board, the Nadi basin had many ponds and lakes, all usually shallow and all generally permanent.
Mountain View, behind the Bounty Hotel was a lake, the Fasa area was a long pond, the land where the back road now is was a large series of lakes as was the Transville area, Nawaka and Nakavu and the areas behind the Hotel Kennedy and behind Namotomoto Village.
All these were created by depressions in the Meigunyah Beds, depressions that still remain today. The problem with all these areas is that people saw them as nice dry (and inexpensive) land and they built on it.
Many of them bought land that had been subdivided; others just created an informal village. AFL even subdivided land at Transville Road, land that had a long history of flooding, and sold it off.

NADI TOWN
The commercial district known as Nadi Town is now regularly flooded and the cost to businesses is great. In recent times there has been a move away from the town to other commercial areas developing along the Queens Road corridor. But this has been slow.
Those who are still in the town have obviously weighed the risks but have, for commercial reasons, decided to stay put even though they know that they will be flooded, on average, every three years.
With the building of the new Nadi bypass road from Navakai to Namaka, the logic of staying in Nadi Town is further weakened.

THE ANSWER
What can be done about the flooding?
The answer is, not a great deal. And there are a number of very sound reasons why this is so.
The biggest problem is the Meigunyah Bed structure thatis basically flat, impervious to water penetration, directing all the surface runoff into the river systems.
These rivers are not able to handle the volume of water that is pushed into them from the whole valley and upper catchment area. The river system, as it is, will never be able to handle the water volume created by short-term heavy rainfall. It never could.
The Japanese government, as part of an aid programme for Fiji in 1980, commissioned and carried out a huge study of the flood problems faced by the country, not just for Nadi but for a number of other areas as well.
This study was carried out over a lengthy period of time by world experts in the area of hydrology, and a large and very detailed report was prepared.
The report made a number of recommendations for the Nadi Basin.  While some recommendations have been put in place, some of the most important have not.
In essence, what the report looked at were ways to assist the river systems in the Nadi basin to cope with the volume of water during a flood event.
There were a number of important actions that were needed to alleviate flooding. One was the relocation of the population in high-risk areas.
While there is a trickle of relocations, no serious action has been taken.
Most of the problem is the resistance of the people located in these areas; they simply do not want to move. This is based on many issues but the most important is financial.
People and businesses want to be compensated to move, often for an inflated figure, and in the residential areas there is the feeling of friendships and relationships that are important and will be lost with moving.

OVERFLOW
The report also accepted that the system as it exists could never cope and made recommendations that would assist in the evacuation of the floodwater within controlled areas.
This basically called for overflow systems that would take the water in the rivers, once it reached a critical height, and use means other than the river itself to shift the water into the sea,.
The major The main recommendations were never implemented.
The most important was the construction of a flood bypass to run basically from the river along the line of Enamanu Road beside McDonald’s from the river to the sea at Wailoaloa where it would discharge into the sea. Both ends would be controlled by floodgates to seal off the road in normal times.
This bypass would take vast volumes of water out of the river above Nadi Town and would reduce the levels downstream.
At normal times the road could operate for traffic but in floods it would be capable of moving vast amounts of water.  This technique is used in many places worldwide and is the main flood protection in southern California and in parts of New Zealand.
One of the issues with this solution was the cost of buying the land, but if the existing road was used as the floodway, costs could be dramatically cut.
There was to be another diversion channel below Nadi Town. The Otuna River (locally called the Qeleloa ) meets the Nadi River head on and the flow pushes the water of the Nadi River back up to the town in times of flood.
A so-called “short cut” channel was proposed that would take the Nadi River west before the current junction and re-enter the stream below the junction.
As well as removing the threat posed to Nadi Town by the backup, the short cut will create a siphon effect when it rejoins the river and will assist in speeding both the flow of the Nadi River at the town and the Otuna River as well.

NADI RIVER
Below that the Nadi River delta is capable of draining immense volumes of water into the sea. It has already been dredged out into the bay. No firm figure is available but it is estimated that around $11 million has been spent on the dredging work in the Nadi River, but recent events bring the effectiveness into question.
Poor maintenance of the drainage system is also blamed for the problem and there is some truth in this, but the real issue is that excellent drainage work has made large tracts of land dry for long periods of time and they only flood now during a major flood event rather than all the time as in the past.

NADI BASIN
Another strategy that has been started by the government is the development of the Nadi Basin Catchment Area Scheme. This involves a series of dams on the waterways that feed into the Nadi River upstream in the valley.
The idea is that in sudden heavy downpours the water can be contained for some time and not immediately released into the river, thus limiting the volume that causes the flooding problems.
It ultimately has to be released (or it overflows anyway) but the delay will buy precious time for the river to dispose of the water from other areas. In addition, in dry periods the stored water can be released under control to provide for the needs of farmers along the river.

THE APPROACH
If the Nadi River floods are to become a thing of the past, a holistic approach has to be taken and action has to be positive, ignoring the resistance of those who have vested interests, for the benefit of the greatest number of residents. And it needs to be done by a body tasked by the Government to achieve the results quickly and permanently.
There are a number of different groups involved in different areas of the issue at the moment, but co-ordination appears to be limited and there is a significant amount of effort and money spent in areas such as awareness and forecasting for early warnings rather than aiming to overcome the problem.
Current history would suggest that Nadi will face the situation again in the near future unless real action is taken.




Fiji Sun Instagram
Fiji Plus
Subscribe-to-Newspaper
error: