Role of transportation infrastructures on the alteration of hillslope and fluvial geomorphology

Abstract

Transport network infrastructure interacts with the earth’s surface because they often share common spaces (e.g. river valleys), such that transport is an anthropogenic pressure that can affect geomorphological processes and outcomes. Since having its profound effect worldwide, the systematic study on the effect of transportation infrastructures (TIs) on the alteration of geomorphological forms and processes has been less focused than on any other anthropogeomorphic driver. The present review provides a multidimensional overview based on the available literature and data on the effect of TIs in changing hillslope and fluvial geomorphology to sustain a peaceful harmony between the transport network and its surrounding landscapes. The study underlines the effect of major TIs like trails, roads, railways, tunnels, causeways, waterways and airports on the alteration of different geomorphological processes on hillslope and fluvial landscapes like the movement of earth material, geomorphic connectivity, slope instability, sediment production, gully initiation and surface runoff. For instance, the global level proximity analysis shows ~40% of landslides happen within the 500 m of any major roads only, while at the regional scale it becomes ~65% irrespective of the degree of seismicity. Due to the fast development of TIs, the mountain regions are more prone to slope instability because of the alteration of surface hydrology by increasing runoff, road and ditch guided concentrated flow, rills and gully formation by reducing drainage area to cross the critical threshold limit. The plain regions are primarily facing the problem of fluvial (dis)connectivity because of the close proximity between river and transport networks and undersized causeways. For sustainable TIs development, factors like the practice of bio-engineering for roadside slope management, de-culverting, 100-year flood return for causeway construction, mapping of river corridors, road water harvesting should be incorporated for less effect on hillslope and fluvial geomorphology.