The Samaan Grove Wetland System

Creating the Wetlands

by Kevin Kenny

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The large version of this diagram opens in
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the water flow as you read. >

The New Drainage System

From the southeastern corner of the estate, waste water makes its way down a newly constructed concrete drain (D1). Surface water runoff from the estate's northern lots flows into the concrete drain at the back of each property.


This drain ends at the silt trap. All of these silt traps were designed to be easily cleaned using a backhoe. Although not installed at the time of this report, there is a plan to place a litter barrier just above the eastern trap to collect any floating debris that washes down this drain.

Because most of the runoff currently comes from a pasture upstream there is little trash in the drain at this point in time. From here the water flows into the first of the constructed wetlands (SWW#5). This wetland is only 1 metre (3 feet) deep and was planted with rushes taken from the immediate area. It is the first natural sediment trap for suspended solids and as such it is expected to fill in, requiring cleaning and de-silting on a regular basis. The initial design worked so well that, in the first high flow situation, the entire bog filled up and had to be dug out and replanted.

From here the water then flows into Lake 1A (L1A) which is 4 metres (12 feet) deep and is meant to dramatically slow the flow of water and allow some sediment to fall to the bottom. The water next flows through a culvert located under the bridge (B1) or through a self-leveling pipe buried deep under the road at a depth of about 3.5 metres (10 feet). The self-leveling pipes were installed under both bridges to ensure that, when the level of the lake falls below the culvert, both sides of the Lakes 1A-1B and Lakes 2A-2B are always at the same level.  

< Lake 1A soon after completion

and a year later, after it had settled and the waterlilies had started to grow. >

The land beside Lake 1B hosts one of the signature samaan trees from which the development takes its name. From here the water passes into the second wetland (SWW#6) flowing through a 15 centimetre (6 inch) PVC pipe. The height of the pipe is set to keep water flowing into the wetland throughout the year. In times of flood the water will flow over the spillway completely bypassing the wetland system. The photograph below left shows soap suds at the end of the spillway indicating the level of nitrates and phosphates contained in the water.  

Samanea saman 


The volume of water flowing into SWW#6 can be adjusted by changing the height of the inlet in the supply pond L1B, above right. We continue to experiment with the water flow as the objective is to always have water flowing through the wetland even during the driest months of the year.   

< This shows wetland SWW#6A when it was first constructed --

-- and one year later. This pond was planted with Vallisnaria which now covers 60% of its bottom. >

Next the water flows down an earthen drain into the second section of wetland SWW#6B. This bog has a wide range of plants growing on a shelf that was built on the northern side of the pond. The shelf was sealed with clay and covered with 15 centimetres (6 inches) of topsoil to speed up the growth of the plants. During the rainy season this shelf is covered by a foot of water. It was designed to grow a host of different bog plants meant to create a diverse habitat. Although only a year and a half old, black-belly tree ducks and the common gallinules have been observed with young in this area. The bog is one of the most beautiful as it winds its way down to the second lake system L2. 

SWW#6B in its first year, just before it was filled
with water

Because there was not enough water coming into the system we had to pump water from Lake 2B the first year.
Water flows into Lake 2B, then down the spillway into an earthen drain which goes through the estate.

Spillway from SWW#6 to Lake 2B

^ Spillway from
Lake 2B >

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