The significance of the riparian zone in forest land management: A project presented in partial fulfilment of the requirements of a Diploma in Natural Resources from Lincoln College

Abstract

The mechanisms governing the production of storm runoff have been a controversial topic since Horton first published his classical theory of overland flow (Horton, 1933). In response to the deficiencies in this theory, another concept was put forward (Hewlett, 1961; Betson, 1964) stating that storm runoff originates only from certain areas within the catchment. The most important of these is the land in the riparian zone, immediately adjacent to the stream channel. The recognition of an active zone and a passive zone in a catchment has implications that go beyond the explanation, prediction and man­ipulation of flood flows.

Kunkle (1974) suggested the concept may be useful in the prediction and prevention of water pollution resulting from the spraying of pesticides and fertilisers. Similarly Engman (1974) discussed the potential of applying the concept to the manipulation of water yield.

The practice of leaving unlogged buffer strips along streams is widely, although not universally, accepted as an integral part of production forestry management in the U.S.A. and in Canada, and is written into forest management procedures in both countries. (Stoddard, 1978; Ontario Ministry of Natural Resources 1973). Emphasis is placed on preventing the entry of sediments into streams, and protecting fresh­water fish habitats during logging. This is a practical application of an active-passive zone concept that preceded formal development of the partial contributing area concept.

Differential, rather than blanket management of catchments may well be a viable proposition for water resource management as well as production forestry. This paper reviews the literature relating to the management of small forested catchments, comparing the New Zealand and overseas experience. It attempts to identify situations in which manipulation of the vegetation in the riparian zones may have a significant effect on the system's response, when manipulating the hydrologic response of the catchment and in the management of production forests where artificial stresses have been imposed on the system. Some general findings, indicating situations when selective management of riparian zones may be effective, are presented.