ASSESSMENT OF RIVERINE DEGRADATION

Abstract

Sri Lanka is blessed with one hundred and three rivers that originate from the central hills. Onlya few of these are perennial. Eighty flows through the dry zones of Sri Lanka. Mahaweli is theonly perennial river that traverses the Northern Dry Zone. Under the Mahaweli Restructuring &Rehabilitating Project (MRRP), Mahaweli Authority (MA) is to be transformed into a MahaweliRiver Basin Management Agency (MRBMA). The key issue that needs to be addressed by thisproposed agency has been identified. Riverine degradation has been one of those

MA's pilot activities on river basin management have been concentrated to the Kala Oya Basinthat includes System H as well. Thus considering Kala Oya Basin as a pilot study area aframework has been proposed to assess the riverine degradation.

Riverine zone includes river/stream banks and river/stream reservations. In addition to thedirected human impact on this zone the activities that take place in the river/stream alsoinfluence the health of the Riverine zone. Further variation in flow regime and velocity too,influence the status of the zone.

While outlining the causes of riverine degradation, the paper highlights the importance ofassessing four components, vegetation, land, stream flow and human that influence the levels ofdegradation in the riverine zone.

Finally three indices have been proposed to assess the levels of degradation in the riverine zone.