Hearn, Gareth
(1987)
An evaluation of geomorphological contributions to mountain highway design with particular reference to the Lower Himalayas.
PhD thesis, London School of Economics and Political Science.
Abstract
Mass movement, fluvial erosion, sediment transport and earthworks - induced instability, often pose major problems for highway design and construction in mountain terrain. This thesis examines the contribution that geomorphological techniques can make to the evaluation of these hazards for highway design purposes in the Lower Himalaya.
A review of the consequences of geomorphological hazards to highway stability is illustrated by reference to selected mountain roads in India and Nepal. The design, stability and construction costs of these roads are discussed in respect to their status or function in the road network and, more particularly, the severity of hazards and terrain conditions they encounter. Techniques of hazard and terrain assessment for highway design purposes are examined and tested in the remainder of the thesis.
Techniques of medium-scale (1: 10 000-1: 50 000) landslide hazard mapping and large-scale (greater than 1: 10 000) geomorphological ground survey are discussed and tested in the Dharan-Dhankuta area of Nepal, in terms of their ability to provide useful information for alignment design, road stabilization and protection works. The contribution of geomorphological ground survey to highway design is critically assessed by reference to the Dharan-Dhankuta road, and its stability following a high magnitude storm in 1984.
A proforma method for assessing flooding, erosion and sediment hazards in small mountain channels is developed. Discharge data for the 1984 storm are derived from these proformas and used to test a number of selected ungauged catchment equations, and to develop empirical relationships between peak discharge and catchment variables for purposes of high magnitude runoff prediction from small catchments. In addition, low-cost, low technology methods for monitoring discharge, slope erosion, sediment transport and mass movement are tested in terms of their ability to provide meaningful data in the short-term for design purposes.
Finally, optimum strategies of hazard and terrain assessment for highway design are proposed. The potential for further application of geomorphological techniques and expertise to mountain highway design is discussed.
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