United Nations report cites unplanned development for woes
SHILLONG: Faulty drainage system has added to the problem of flooding of several areas of the city due to rain.
Frequent rain has also caused landslides in parts of the city.
A report of the USAID and UNDP released in Shillong and available with The Shillong Times , has confirmed this.
The report said the city witnesses flash floods during the monsoon season, due to high intensity rainfall for prolonged hours. Other important factors responsible for flooding in the city are the clogging of drains and insufficient capacity of the rivers flowing through the city area. (See Sunday Shillong)
“Due to heavy downpours during the monsoon season, the water tops the banks along most of the streams causing flooding in localities in the vicinity of these streams. This is aggravated by a drastic reduction in channel capacities in most streams due to encroachments along their banks by buildings”, the report said.
The city is drained mainly by the upstream reaches of Wah Umiam, Wah Umkhen, and Wah Tamdong Rivers. Most of the drainage lines in the area are first, second, and third order reaches of these rivers, it said.
The report said the areas which have drainage congestions causing flash floods are Wah Umkhrah- Mc Cabe Road, Polo Market, Don Bosco Road, NH 40 Weiking Pdengshnong, Budha Mandir Road, Veronica Road and Dhankheti Junction. It has also been observed that drains are not in good shape at many places along the roadside.
“At several places, rainwater simply flows onto the roads and many of the roads are without any drains. Dumping of garbage and waste materials at unauthorized sites and on roads clog the drains, which subsequently cause water logging and increasing the flooding problem”, the report said.
According to the report, the objective of flood hazard assessment is to demarcate the flood-prone area and assess its intensity and magnitude. Flood-prone areas are those subjected to inundation at a regular frequency.
The team entrusted to study the matter has considered detailed impact in the river basin and the presence of various hydraulic structures in assessing the riverine flood hazard.
The flood hazard assessment framework that has been adopted for the study comprises of identification, acquisition, compilation and review of all the relevant hydro-meteorological and biophysical data. The data includes terrain, soil, land use land cover, runoff/river discharge and flood protection measures to form the input for the model. The study focused on the assessment of localized flooding, delineation of drainage flow lines within the city boundary.
Landslides
The report said the Municipal areas of Shillong are less prone to landslides as compared to neighbouring areas and approach roads to the city. According to the report, there were four historical landslides in the past which are in the left bank of Umshyrpi river near Lumlyer and the remaining three landslides happened due to human interference.
The report said in the recent past, landslide vulnerability increased due to unplanned and unscientific development, deforestation, chocking and blocking of natural drains, poor road construction, and encroachment on steep hills.
Some of the localities which have experienced landslides in the recent past are Madanriting (2000) Nongrimbah, Lawsohtun and Happy Valley (2007), Lumsohra,Laitumkhrah (2008), Macabe road, Polo, Bethesda, Kench’s Trace, Arbuthnot road, Wah Kynrud, Raid Laban, Um Saw, Lumparing, Jackson Trace Road, MES road, and Sericulture Farm.
The report said that it is evident from the analysis that the rainfall intensity is projected to increase by 22 per cent in Shillong by the end of this century. The increase in precipitation is projected to be highest during the pre-monsoon and monsoon seasons. This clearly suggests that both heavy and very heavy rainfall episodes during the pre-monsoon and monsoon seasons are likely to occur in Shillong more often than now by the end of the 21st century. This could have serious implications in terms of more frequent and severe floods in Shillong in the future, the report added.