I need information
What are the common misconceptions about Storm Water Drains (SWD)?
What are the reasons for flooding?
What are the implications on Health and Hygiene?
Can BMP and the citizens' work together on controlling the adverse problems related to the Storm Water Drains?
Back to Storm Water Drains
Email Webmaster
What are the common misconceptions about Storm Water Drains (SWD)?
The two common misconceptions about SWD's are:
• That they are garbage dumps; and
• That they are open sewage drains.
Increasing development pressures within the core area have been accompanied by a general neglect by private and public institutions of even the basic flood protection function of a drainage system. Based on preliminary inspections and discussions with the BMP, less than 20% of the main drains in the BMP Area have earth banks and even these are generally disturbed and eroded.
The design standard for main drains in the core area is extremely low by accepted standards for a large city. The high topographic relief in most valleys limits the extent of the population affected by flooding to those that are adjacent to the drains, the flatter drain reaches and the low-lying areas, particularly adjacent to tanks.
What are the reasons for flooding?
Principal factors contributing to the flooding problem in Bangalore are:
• Inadequate control of layouts (land development) and buildings with respect to easement
provisions and floor level controls
• Inadequate culverting at major and minor roads
• Obstructions by sewerage works in drain channels
• Restrictions caused by cross service lines, including water supply, power and telecom
utilities
• Illegal and inappropriate encroachment of buildings obstructing waterways
• Accumulation of solid wastes and sediments in the drains
• Low design standards for drainage, combined with the absence of appropriate data and
analysis techniques.
A general lack of appreciation of the potential values and importance of waterways in the urban environment combined with fragmented management arrangements and an inadequate funding base, now threatens the waterways in the rapidly developing lands outside and downstream of the BMP catchments.
Although a BWSSB sewerage system is provided in many drainage basins in the core area, there are still large quantities of raw and minimally treated sewage flowing in the urban drains and accumulating in tanks. This is caused by a combination of:
• Wastes directly discharged into the drains from connected buildings;
• Branch sewers not connected to the trunk sewers; and
• Effluents from trunk sewers, which have a low capacity due to siltation, or higher than
planned development densities, are let in.
One significant factor contributing to frequent flooding of low-lying areas and to unsanitary conditions in drains and tanks is the large and rapid accumulation of sediments in the drains. BMP has removed some 15 years of accumulated silt in recent years. Insufficient collection of solid wastes and a lack of understanding of the impact of casual litter disposal in drains are significant factors contributing to the high silt and debris volumes found in drains and tanks. Similarly, lack of erosion control practices in construction sites, public parklands, and private gardens, and on the medians and verges of roads encourage heavy silting in the main drains. These factors, combined with infrequent clearance of drains, have led to the reduced capacity and unsanitary conditions in drains.
What are the implications on Health and Hygiene?
Inadequate drainage causes inconvenience and loss to the citizens of Bangalore. In its most severe form it leads to flooding of houses and establishments in the floodplains. In its least severe form poor drainage causes water stagnation that provides a breeding ground for mosquitoes and leads to generally unsanitary conditions. The importance of adequate storm water and wastewater drainage, in tandem with sufficient water supply, cannot be over-emphasised, in ensuring good health and hygiene to citizens.
Can BMP and the citizens' work together on controlling the adverse problems related to the Storm Water Drains?
In order to maintain a good drainage system within the city, the following points are important:
• All constructions, whether private or public, must not encroach on low-lying waterways or
drain paths.
• Care must be taken to prevent silting due to disposal of construction debris.
• New constructions must be monitored to prevent upstream or downstream flooding.
• Unwarranted acceleration of erosion due to various land development activities must be
controlled.
• No new construction should be permitted until temporary or permanent erosion prevention
and sedimentation control management practices are implemented and are operational to the
BMP's satisfaction. BMP must be vigilant in stopping stop constructions that do not have
erosion prevention and sedimentation control measures.
• Construction in floodplains should be done in a manner that protects or enhances storm
water quality and promotes land and tree conservation.
• Sewerage drains from dwellings must not be let into storm water drains.