Preserving Disappearing Water Bodies
This article was published in The Financial Express on January 11, 2016.
An abridged version of this article was also published in Huffington Post on January 2, 2016.
Recent floods in major Indian cities have been largely blamed on water body encroachments. Madras High Court has ordered that no more encroachments be tolerated on water bodies. By constructing buildings on water bodies and runways on wetlands, we have damaged our natural drainage basins. The rate of disappearing water bodies and wetlands is reaching an alarming level. Disappearing water bodies have impacts beyond the environment and spills into the socio-economic arena. It is paramount that we take immediate actions to identify our waterbodies, study the rate of disappearance and take actions to reverse this course.
Before we begin to discuss potential solutions, one must start with identifying the problem. Today’s Geographical Information System (GIS) and Remote Sensing (RS) technologies can help with tracking the waterbodies, detecting changes using remote sensing, performing temporal analysis to view the rate of disappearance in a dramatic way, and measuring volume loss of water bodies. These techniques will provide a true picture to decision makers, allowing them to make appropriate policy decisions.
Tracking water bodies must start at a Local and Regional level. A number of methodologies can be used including Satellite Imagery, Field Data Collection using GPS, and Aerial Photography. Indian Remote Sensing Satellites provide highly accurate satellite imagery for end users. GPS technologies provide sub-centimeter accurate data and Aerial Photography provides centimeter level data. This data, once collected, then can be used to create GIS maps of the waterbodies. Accompanying figure shows a map of water bodies derived from a Satellite Image. When analyzing disappearing water bodies, it is important to capture data on a periodic basis allowing one to get an accurate depiction. For urban regions, it is recommended that water bodies be mapped twice a year at a minimum. A process must be set up such that these areas are mapped on a routine basis. This can be accomplished by setting up a task force for the water body mapping project or assigning a research team at a nearby higher education institute. Once these areas are mapped, it will allow us to quantify change by calculating change detection statistics. A number of large scale studies have been performed over the years including a study by Tufts University for Central Asian water body Aral Sea. Author Jeffery Trull used historic aerial imagery to perform remote sensing analysis to detect change. Another study by University of Queensland for small water bodies in Ghiduari Mouza of Atpara Upazila authors Dr. Khondaker Mohammod Shariful Huda, Ummeh Saika, and Md. Al-Amin Hoque, used field surveys to map waterbodies. Authors were able to detect significant changes, and because they were using field surveys, they were also able to pinpoint reasons for these changes. Some of the reasons include settlement, plant residuals, encroachment, drainage, and sedimentation.
Once change is detected, visualizing these changes for policy makers is important. One of the more effective tools for such visualization is Temporal Analysis. Making the mapped data layers “time aware” (a “time aware” data layer has time stamp for the data when it was created) will allow the analysts to perform spatial temporal analysis. A temporal analysis allows one to view change in “time aware” data at a different point in time. It essentially is a “time-lapse” video of the water bodies and provides a clear before and after contrast. A temporal analysis will allow the analysts to look at change over a specific period of time throughout the region, change for a specific water body for the entire time span, etc.
Once the waterbodies are identified and we can conclusively show the disappearing effect, the challenge then becomes how do we slowdown the process. A scientific study that shows the true causes of disappearance leaves little room for political debate. This allows the policy makers to make recommendations in a more objective fashion. A number of policy tools are available to save the waterbodies from disappearing depending upon the identified cause. These include land use regulations that protect wetlands, enforcement actions against encroachments, development master plans that protect waterbodies, regular maintenance of waterbodies to clean sediments and plant residuals, improvement of drainage infrastructure, general awareness programs that encourage public participation, etc. We shall also mandate Environmental Impact Assessments on major construction projects such as airport runways. It is clear that an objective Environmental Impact Assessment would clearly identify potential pitfalls of building a runway on wetlands.
The spotlight put on water bodies encroachment problem in our metro by the recent flooding in Chennai offers an opportunity for us to undo years of damage. We must take urgent actions to reverse the trend before it’s too late. GIS technology plays an important role in managing our natural and manmade water infrastructure. With India’s large population, it is imperative that we take advantage of the technological advances and actively manage our resources.