**3. Case studies**

130 Urban Development

amount of rainfall, the volume of runoff generated, infiltration rates and drainage basin characteristics are neglected during urbanization process. These features are more commonly neglected in the arid regions mainly due to the lack of sufficient data which restricts the modeling capacity for extreme events. Topography is one important parameter which is not taken into consideration during town planning in these regions and instances

Use of satellite imageries, digital elevation models, field observation and geophysical and hydrological investigations can help in reducing the complications related to urbanization in

This book chapter focuses on the elements of hydrology which should be taken care of during urban planning and development with special emphasis on arid regions. A few case studies assessing the hydrological elements for urban planning have been cited as examples

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.

influence the nature of hydrographs and hydrological variables.

survey plan, and drainage network map.

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

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

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

of flash floods and water logging are becoming common due to such negligence.

arid regions.

for arid region models.

**2. Methodology** 

#### **3.1 Delineating the wet/dry zones in the Qassim province of Saudi Arabia (Faisal K. Zaidi et al, 2010)**

#### **3.1.1 Introduction**

Central Saudi Arabia experiences an arid type of climate with mean annual rainfall rarely exceeding 150 mm. The low rainfall has resulted in scanty vegetation in the region except for the wadis where farms and date palm plantations can be seen due to the availability of groundwater. However the chance of flash floods increases to a great extent due to lack of vegetation cover in the events of heavy rainfall.

The city of Buraidah which is the administrative capital of the Qassim province has undergone rapid urbanization in the recent years and due to lack of proper urban planning a lot of low lying areas and stream channels have been allotted to housing colonies. During the heavy rainfall in the month of November 2008 and March 2009, many such housing colonies in the low lying areas were inundated by flood water.

The stagnant water in the lakes became a threat for the environment by providing the breeding ground for mosquitoes and other water borne disease. Thus it was decided to drill a few bore wells in these manmade lakes with the dual purpose of recharging the aquifer and getting rid of the stagnant surface water thereby preventing environmental degradation.

Assessing Hydrological Elements as Key Issue for Urban Development in Arid Regions 133

Fig. 2. Location map of Buhairatil Khaleej with the direction of the survey line

6 may be due to the presence of less weathered limestones.

Figure 3 shows the result of the resistivity survey. The resistivity values range from 7.07

The depth of investigation in the present case is about 72 meters. The resistivity value for the total depth of investigation does not show a very high contrast and in general is very low ranging from 7 ohm.m to 37 ohm.m. indicating the presence of a wet zone throughout the entire depth of investigation. However at a depth of about 30 meters from the surface the resistivity value increases indicating the presence of relatively dry zone. This boundary (Figure 4) can well be the contact zone between alluvium and weathered limestone as the site is situated in a stream channel. The 2 zones of relatively high resistivity shown in Figure

Result

Conclusion

ohm.m to 36.9 ohm.m.

Electrical Resistivity Survey was carried out at 4 locations (Figure 1) for investigating the depth of the wet zone in these localities. Based on the depth of the wet zones the approximate depths of injection bore wells were estimated.

Fig. 1. Location of the 4 localities in Buraidah, Qassim
