Due to the increasing forms of environmental degradation, many countries have realized the importance of safeguarding their natural resource bases and have made such management actions like river rehabilitation their priority. This project report explores and analyses the challenge of cleaning and maintaining Mathare River in the face of the Mathare slum settlements in Nairobi. It was carried out between September 2013 and April 2014. Mathare River is one of the three rivers within the Nairobi River Basin with the other two being Motoine/Ngong River and Nairobi River. The research was based on three specific objectives, which are; finding out the approaches applied in cleaning and maintaining the river; finding out why the slums are a challenge to the rehabilitation process and to find out whether it is practically possible to restore and maintain a 30m meter riparian zone in the presence of the Mathare slum. Household questionnaires, focus group discussions, direct observation and field photography were the primary sources of data while the secondary sources of data included institutional interviews, published reports, magazines, journals and websites. The findings showed that the NRBP was a multi-stakeholder initiative. The Mathare slum settlements pose a challenge to the cleaning and maintenance of the river in a number of ways including by encroaching into the riparian zone, improper waste disposal (evidenced by the 77% and 81% of the respondents who dispose solid waste and liquid/fecal waste directly into the river respectively) and unsustainable uses of the river. Another major finding was that residents who have stayed in the area for over 20 years have developed a sense of attachment to the land. This therefore would make it a daunting task to evict these residents for the clean-up project to be successful and sustainable. Finally, the report does recommend some feasible alternatives to some of the approaches highlighted by the NRBP. iv These include among others the implementation of Integrated Village-Level Planning to facilitate the provision of essential infrastructure within the Mathare slums.