The Water Resources Authority (WRA) is reporting that the flooding affecting sections of Content in Williamsfield, Manchester, is due to a significant rise in groundwater levels in the local aquifer system.

Groundwater measurements from the Content borehole indicate that between September 25 and November 3, Jamaica’s groundwater levels increased by about 100 metres (330 feet).

The rise occurred as the country received heavy rainfall before and during the passage of Hurricane Melissa on Tuesday, October 28.

Managing Director of the WRA, Peter Clarke, told JIS News that the occurrence is not unfamiliar for the area, with the last notable occurrence being in 2002 after a period of heavy rainfall. He explained that while some rainwater runs off on its own through different channels, most of it is absorbed into the ground to make up the country’s groundwater reserves.

“If it becomes a case where the water that is soaking into the ground is more than the rate of flow that the groundwater can accommodate then, instead of flowing away, it rises. Groundwater doesn’t flow as fast as river water so, when you see it raining and the river is a raging torrent as it goes downstream, your groundwater moves a whole lot slower than that,” Clarke pointed out.

The data show that the surface flooding comes from the active upward movement of water through a nearby sinkhole.

“Picture that the whole Content area is a very large bowl, and the water has been coming underground and from the side and then it breaks through the side of the bowl, basically. In this case, we have determined that it is rising through sinkholes that would normally take water away, but it is now using the sinkhole as a conduit to rise up,” added Clarke.

The WRA has installed a flood gauge in the area and has begun routine monitoring of water levels. Current observations show that the floodwaters are rising at an estimated rate of 0.014 metres (0.046 feet) per hour, based on measurements taken on November 3.

“[This] translates to just under a foot [of water] per day. So, it is presently rising. How high it will rise will depend on, for instance, if we get more rain later in the week and how long it will stay will depend on how fast it can eventually flow away,” Clarke told JIS News.

The WRA will continue to monitor the situation closely and provide updates as conditions change.  However, the rise is expected to continue until groundwater levels stabilise. “This is just a natural phenomenon. The physicality of the hydrology that is there is not anything that you can or would want to do anything to try to stop,” Clarke pointed out.

Assessments have also begun in the Comfort Hall/Evergreen areas of Manchester, where groundwater has historically risen and caused property flooding.