ANALYTICAL STUDY OF FLOOD PROBLEMS AND GROUNDWATER RISE IN THE JEDDAH DISTRICT

 

BY

 

Tariq H. Bayumi, Mahmood S. Alyamani, Ali M. Subyani, Abdulrahman M. Aldakheel, and Masuod E. Alahmadi

 

Hydrogeology Department, Faculty of Earth Sciences, King Abdulaziz University

Project No. 606/418

 

SUMMARY

 

The aim of the present work is to recognize and examine the factors that are causing the flooding and groundwater level rise in the city of Jeddah and the impacts thereof. Detailed investigations have been carried out concerning geological, hydrological, hydrogeological and hydrochemical aspects prevailing herein.

The study indicated the existence of a continuous aquifer that consists of various formations. Several sources are recharging this aquifer, among them leakages from water supply pipes, cesspools and water storage tanks in addition to subsurface inflow from the eastern wadies and infiltration of irrigation water. The rate of groundwater level rise is variable from one district to another according to the intensity of population.

Maximum daily rainfall records for 35 years were analyzed using the log Person, Type-III method to construct the rainfall frequency curve. Furthermore, the flood volumes and peaks were calculated for 13 wadies east of Jeddah and for various return periods. Urbanization within these wadies was considered the most important factor controlling the flood magnitude.

     The hydrochemical study indicated that the most important processes influencing the groundwater quality are evaporation from shallow-water table areas, mixing with fresh water and the dissolution of surficial evaporitic salts.

     Serious adverse impacts resulting from floods and shallow groundwater levels have been discussed, such as environment pollution and damages to infrastructures.

     The implemented measures for preventing floods and groundwater rise in Jeddah are the storm drains and the horizontal drainage network, consequently. The efficiency of these control measures was examined and new remedial measures were suggested to overcome the problem.