Riparian Zones and Their Role in Enhancing Resilience to Flooding in Urban Areas

A Case Study of Nairobi River Basin

Abstract

Resilience has been defined as the capacity of a system to absorb disturbance and reorganize while maintaining the same function, structure and identity. In Nairobi river basin, storm water drains have been developed to direct floods away from urban developments. However, when upper areas and riparian areas of rivers are bleached, the ramifications are seen in terms of increased flood resistance that reduces resilience. The main objective of the paper is to investigate the role of functional riparian zones in enhancing resilience to flooding in urban areas. Specifically, the study examined whether there are developments that are at a permanent risk of floods as a result of ignoring potential role of the riparian zone. Secondly, the criteria used during delimitation of riparian zones was assessed in its adequacy to shield development from effects of floods. Data was collected using mapping and archival methods. The study established that the width of the river varies along the river profile and depends on the adjoining topography. The location of the high-water mark therefore is not constant from the river and widens or narrows depending on the adjoining topography. The study revealed that there are structures that are at permanent risk of flooding. It was further established that the criteria used during delineation of the riparian zone is not adequate to protect development from flood hazards. Areas where structures are constructed within defined active flood areas are constricted and they have blocked the flood paths. As a result, floods get elevated due to lower rate of evacuation causing localized flooding in areas not ordinarily affected by floods. The paper concludes that functional riparian zones have potential role of ensuring flood resilience. The study recommends regeneration of the active flood areas through relocation of structures and planting of trees. The study further recommends pegging of inundated flood areas based on the criteria established in the study.