Lacustrine shore platforms at Lake Waikaremoana, North Island, New Zealand

This paper examines the morphology and processes governing the development of shore platforms at Lake Waikaremoana, North Island, New Zealand. Shore platforms at Lake Waikaremoana are recent features, and were formed when a new sequence of shoreline development was initiated, due to lowering of the lake by 5 m in 1946 for hydroelectric power development. Three predominant platform morphologies were identified around the lake. These include gently sloping platforms (c. 1.5 to 3.9degrees), ramp platforms (c. 6.8 to 9.2degrees), and concave ramp platforms (c. 7.9 to 12degrees). Platform widths ranged from I I to 31 m, with the gently sloping platforms characterized by the widest morphologies. Erosion rates were estimated using perched sandstone boulders and were found to range from 3.4 to 12.5 mm a(-1), with a mean erosion rate of 5.9 mm a(-1). Higher rates of erosion were identified at lower platform elevations, due to a greater frequency of wetting and drying cycles coincident with storm waves, while lower erosion rates were identified at higher elevations. Field evidence suggests that shore platforms at Lake Waikaremoana were likely initiated and continue to develop as a result of subaerial wetting and drying cycles. Waves, coincident with fluctuating lake levels, play an important role by removing the weathered material from the platforms, and appear to control the width of the platforms. A conceptual model of platform development is presented, and analogies are drawn between this model, and the formation of shore platforms in oceanic environments. Copyright (C) 2002 John Wiley Sons, Ltd.