**2. Methodology**

To implement the above mentioned tasks, the scientific methods adopted are mainly GIS based, confirmed with field measurements in the site under study. Nowadays the use of modern remote sensing technologies with the help of satellite imageries such as SRTM, SPOT 5, IKNOWS, QUICKBIRD, supply detailed coverage with resolution of 90, 20, 10 and 1 meter respectively. Digital Elevation Models (DEM) can be worked out to visualize in three dimensions, the topography and, drainage, flow direction and undulations on the topography of the area under study. An initial pilot visit to the area is needed to observe the major features of the area, the ground conditions including rock and soil type. Pounding areas and potential pounding areas to be figured- out and located. Analyses of collected topographic maps for identification of natural drainage of the site and the surrounding areas, and delineation of the catchments boundary are a necessary step in these procedures.

Collection of meteorological data (precipitation, temperature, evaporation, wind speed and directions) and topographic maps is an important aspect to evaluate the climate and hydrology of the area. This is followed by processing of collected data. The data are presented in tables and graphs. Mean, maximum and minimum of each variable are calculated. Rainfall distribution maps, frequency analyses, estimation of surface runoff are worked out. The maximum rainfall and run-off generated should be taken note of.

The above mentioned accomplishments are then subject to detailed desk study. The baseline data thus include: site overview plan, satellite image of the area, DEM, site topographic survey plan, and drainage network map.

The methodology involves carrying out detailed morphometric analysis of the basins within the area under study. Morphometric parameters such as basin shape and basin relief influence the nature of hydrographs and hydrological variables.

Based on the result of the hydrological processing identification of flow direction, flow accumulation and stream generation can be obtained and drainage channels can be classified into different orders using Strahler's 1964 classification. Other basin parameters such as basin area, basin perimeter, basin length and stream length are further used to obtain the different ratios such as Drainage Density, Bifurcation Ratio, Stream Frequency, Form Factor, Elongation Ratio, and Circulatory Ratio.

Ground surveys include essentially preparation of a geologic map of the area, showing the main structural elements of the earth that may affect the units of urbanization such as buildings, roads etc., and gathering information on the subsurface stratum to depth in the order of few meters to some 30 meters. The subsurface picture can be elucidated using geoelectrical techniques, (Reynold, 2011). A number of instruments are available to achieve this goal. Nonetheless the use of SYSCAL-Pro 72 unit proved to be very useful. Resistivity surveys using multi-electrode resistivity technique gave good results. Dipole-Dipole configuration with the unit electrode spacing ranging from 2.5 meters to 5 meters depending upon the ground clearance can be adopted. Dipole-Dipole configuration is selected for the survey as it gives the best horizontal resolution as compared to all the other methods present. RES2DINV Software, (Loke, 2002) can be used for inverting the apparent resistivity values to a resistivity model section. The least square fitting technique (Loke and Barker, 1996) is used for getting the best fit for the resistivity model by iterations.

Infiltration is another important hydrological element for urban development studies. Field measurements of both infiltration capacities and infiltration rates of the different soil types in the area are necessary to accomplish the hydrological picture of the water budget in the area, (Hopmans, 2011).

All these accomplishments and measurements, as mentioned earlier, should be GIS based so that the different layers can be compared and inter-layer relationships can be worked out. Based upon these relationships the area under study can be zoned according to hazard prone areas as far as hydrological elements are connected to urbanization.
