The recent flooding of the Vuci, Lakena, and Waituri area can be attributed to various attributes including hydrology, land-use, topography, and recent developments, rather than just drainage in the area, Minister Mahendra Reddy provides an update.
MUCH OF THE DELTA IS INTERTIDAL AND OFTEN FLOODED DUE TO THE PLAY OF VARIOUS FACTORS.
The continuous rainfall recently has led to localised flooding of secondary outlet drains which are part of the drainage schemes of the greater Rewa delta.
The Rewa delta, one of the largest deltas in the Pacific Islands consists of a land area of 240 Square kilometers is home to some 70,000 Fijians, the majority of whom live in low lying areas.
In a release from the Ministry of Agriculture, Rural and Maritime Development, Waterways and Environment minister Mahendra Reddy said much of the delta is intertidal and often flooded due to the play of various factors. The areas recently flooded include;
Lakena Area
Vuci Area
Waituri Area
The recent flooding of the Vuci, Lakena, and Waituri area can be attributed to various attributes including hydrology, land-use, topography, and recent developments, rather than just drainage in the area.
Rainfall analysis indicates during the last week of April 2020, 96-hours of cumulative rainfall recorded was 318mm at Nausori Airport Station, and total April rainfall was 685mm, whilst the long-term monthly average (April) for the station is approximately 339mm.
This is greater than double (200 per cent) of the monthly rainfall for Nausori, illustrating the immense amount of rainfall we have experienced last week, especially at a time when the soil was still saturated by rainfall during TC Harold.
Furthermore, the topographically characteristic of the area is low-lying (few meters above average Mean Sea Level) and decreases gradually to the East.
Having such a low gradient restricts water movement along existing drainage, hence affecting discharge.
With the majority of the area, being intertidal the tidal effect on the discharge of the water is far more dominant and pronounced in these areas during the heavy downpour.
Moreover, these areas are topographically low lying, designed for rice farming as part of the irrigation scheme.
As such, these areas were designed to hold water, specifically for rice farming.
What we have seen over the years is the unplanned conversion of rice paddies into housing allotments.
While this has been done, there has been very little done to address the topographical nature of the area before building dwellings on it.
As such, in these areas, during times of high-intensity rainfall events, with increased runoff and saturated soil, the conveyance of the drainage system is overwhelmed and overflows into the adjoining land flooding the area.
While an enormous amount of drainage works has been carried out by the ministry, we still find that these drainage systems are not well maintained once cleared and often filled with white goods, tires, household rubbish, motor vehicle parts, and rubbish, which leads to blocked drains causing floods during heavy downpour.
Has mobilised two excavators to de-silt and remove rubbish blocking drainage.
The ministry is currently carrying out rapid assessment and necessary approvals for the dredging work that needs to be undertaken to address this, after the failure of the existing contractor to carry out scheduled works.
This work shall see the increased discharge of water from the above area, help to alleviate the inundation area during high rainfall events.
Make efforts to maintain existing drains and structures so that water can flow unhindered;
Do not erect the permanent structure in floodplains and low lying areas as these areas will naturally get flooded due to the topography;
Illegal developments must adhere to drainage plans;
Do not dispose of litter and unwanted white goods into waterways and drainage systems;
The ministry wishes to reiterate that excess water on our waterways will continue to overflow into low lying areas and no amount of drainage will avoid flooding as these areas hydrological as such and are below mean sea level.
The community members and members of the public are advised to be responsible with their rubbish and adjacent drainage, specifically those that get clogged by their irresponsive behaviour, flooding them and others in their communities.
We will continue to provide services within our mandate to ensure that Fijians are safe from flooding.