Year

2015

Degree Name

BEnviSci Hons

ANZSRC / FoR Code

0599 OTHER ENVIRONMENTAL SCIENCES

Department

School of Earth & Environmental Sciences

Advisor(s)

Laurie Chisholm

Abstract

The alteration of hydrological regimes through the construction of dams and minor diversion weirs has significant detrimental ecological effects on the downstream river reaches. In the case whereby approximately 99% of the Mean Annual Flow (MANF) has been diverted, the flow regulation has often resulted in a constriction in the river channel and a reduction in complexity of the aquatic and riparian vegetation and encroachment of terrestrial plant species.

The Snowy River Increased Flows (SRIF) environmental flow program aims to return 21% of the MANF to the Snowy River below Jindabyne. This revised flow regime attempts to re-introduce the hydrological cues such as seasonal flow patterns, annual floods and greater daily flow variability. In the case of the Snowy River, a higher magnitude annual flood was introduced to flush sediment and vegetation within the river channel and the more variable daily flow rate aims create a more natural and complex riparian and aquatic vegetated habitat.

This study examined the changes in aquatic and riparian vegetation at two sites in the Dalgety Uplands macro-reach of the Snowy River using four band colour infra-red high-resolution aerial photography in 2007, 2010 and 2013. A supervised maximum likelihood classification to determine vegetation classes and post-classification change detection was used to quantify the vegetation changes. The results indicated than an increase in flow magnitude was able to create a more open water and aquatic habitats. Furthermore an increase in the frequency of inundation across the lower benches increased the abundance of flood tolerant amphibious species and removed water susceptible species. These changes are reflective of the importance of the moisture gradient in riparian zones and the zonation of riparian plant species is largely determined by the flow regime.

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