The effect of urbanization on the drainage system in a semiarid environment

The effects of urbanization and suburbanization on channel morphology have been investigated in two cities, several towns and rural communities in the Mediterranean coastal zone eastwards, including the semiarid Northern Negev Desert, Israel. Examples indicate that channel response is variable. Channels within built areas have often been narrowed but not deepened, hence their cross sectional area has decreased, thereby increasing flooding potential. They have remained fairly narrow. Downstream reaches have remained with their natural hydraulic geometry, being fairly stable after decades of continued increase in built areas. Channels near and within urban areas were found to be neglected, often creating flood hazards. In places, channels have been ignored by planners. It is apparent that mismanagement of channels with a flashy nature and the lack of recognition of the associated problems it presents, poses a flooding hazard to communities in semi-arid to Mediterranean regions, as it does in more humid environments.