Leveraging high-resolution photogrammetry techniques for mapping hydropower potential

Abstract

The assessment of channel stability, landscape hazards and energy potential are important components of the development of micro-hydroelectric schemes however, there is a lack of guidelines for geomorphic evaluations of reach suitability within alpine settings in New Zealand. In this work, I examine the use of stream power profiles, sediment pathway and connectivity analysis, grain size trends, and process interpretations of channel morphology as integral measures of stream stability, and therefore suitability for micro-hydro development. Happy Valley offers a dynamic landscape within the Seaward Kaikoura Ranges of New Zealand, for the assessment of micro-hydro potential for an alpine stream. The steep greywacke slopes of Happy Valley display a variety of bedrock, colluvial and alluvial channel morphologies, offering a good case study area for a comprehensive investigation into the relationship between lateral stream boundaries (Quaternary [glacial] landforms, bedrock walls and colluvial deposits), local stream power and channel morphology. Elaboration of this relationship offers a number of insights into which stream reaches may provide the best location for micro-hydroelectric site development. The downstream trends in total stream power, specific stream power and stream power gradient are modelled along two 600 m long reaches of Happy Valley Stream using high resolution topographic data (<0.055 m resolution) acquired using Structure-from-Motion photogrammetric techniques. Stream power trends were assessed in relation to changes in slope and the degree of channel confinement imposed by the landscape setting. Peaks in stream power were found to be more strongly influenced by slope than by confinement along Happy Valley Stream. Assessment of the stream power gradient and potential geomorphic hazards has led to the development of an optimisation framework for identifying viable sites within steep alpine environments for micro-hydroelectric intake infrastructure. Although previous studies of stream power trends primarily focus on sediment transport capacity and channel stability in lowland streams and rivers, this study has shown how modern topographic techniques can be applied to remote, ungauged streams for assessment of channel characteristics. Where possible, micro-hydro feasibility studies should make use of high resolution surveying techniques to improve characterisation of downstream trends in stream power, and thus better understand the river’s capacity for change. Keywords: stream power, channel stability, morphology, micro-hydro intake, structure-from-motion, high resolution, geomorphic hazard, environmental management, Kaikoura.