Introduction

Unauthorized dumping of urban wastes refers to the open disposal of waste at private or public places other than the designated wastes processing sites [1, 2].  This is now rampant in many rapidly urbanizing cities of developing countries, such as India where the required environmental laws are being implemented slowly and the waste processing infrastructure is being created even more slowly [3-5].  In this gradual transition, there is a need to understand the pattern, and choice of sites and likely reasons for unauthorized urban solid wastes (USW) dumping so that necessary control measures could be suitably effected.  In order to minimize and control such environmentally unacceptable practices of unauthorized dumping, it requires that an inventory of unauthorized USW dump locations is made.  Earlier studies showed that aerial photography interpretations, aerial photographs converted into digital format or temporal remote sensing data were used for identification or for monitoring of waste dump sites [6-13].  The major limitations of using aerial photographs or remote sensing data acquired through space borne sensors is the difficulty to distinguish between general waste materials and the accompanying materials with similar spectral characteristics, identification of waste dump site near hilly or low lying area and the high costs involved in obtaining digital data of such waste sites.  In addition, finding the location of such dump sites based on questionnaires and other local information (newspaper) are limited in scope and scale [14, 15].  Conventional methods of carrying out a physical survey of unauthorized dump sites by trained persons would generally take long periods over which much of the dumped material and its spread would change significantly.  It is believed that this would be the case with Bangalore USW generated 3600 tons/day, which has >70% easily degradable organic material [4, 16].  These approaches have limited potential to detect a large majority of unauthorized dump sites as well as it limits the number of dump sites discovered when study periods are relatively short and dump sites keep shifting freqently.  Locating a majority of such ‘randomly’ created dump sites accurately within a short period is therefore a challenging task. 

The task of rapid estimation is often made easier because a large majority of the dump sites occurs only where there are motorable roads which the garbage laden trucks can drive on to carry out their unauthorized dumping.  Such dumping is generally done using smaller roads which branch off the eight main arterial roads that emerge from the city of Bangalore [17, 18].  This pattern of occurrence and the need for being illegal provide researchers an advantage that such large motorable roads are often visible from aerial photographs and can be used easily to reach and locate these dump sites using handheld GPS (global positioning system) units.  Further, a visual or physical measurement of the size or spread area may quickly be carried out at each location [19-26].  The size and depth of unauthorized dumps vary and such variations in the spread area of dump sites complicate the exercise of area estimation.  It was felt that these limitations could be overcome by carrying out the rapid survey with a large team as well as by employing motorcycle borne surveryors with provision for a limited level of random verification to assess the extent and types of errors.  The approach of rapid large-scale survey has limited reliability and validity due to the limitations of visual assessments [22] and therefore random verifications is required to quantify variations and extent of errors.  As the developing world urbanizes rapidly, rapid surveys of unauthorized dumping practices will be required [27]. 

This research therefore focuses on determining the efficiency and accuracy of rapid identification and assessment of a) dump site locations and its shift with time and b) dump site waste spread area and its composition.  In this study firstly a technique is developed to rapidly identify unauthorized dump locations, second to assess the area of land sacrificed and to compare possible techniques of area measurement and third to estimate the extent and nature of USW reaching such locations.  The limitations of this technique with regards to the accuracy and types of errors encountered have been estimated and described.