The LiDAR revolution in glacial geomorphology: its gifts and challenges

<p>Science progresses when we are afforded with a ‘better look’ at nature. For geomorphology, the production over the last 100 years of an ever-increasingly resolved view of landscapes with topographic maps, DEMs, remote-sensing images, etc. has always been accompanied by new geomorphologic discoveries. LiDAR images of formerly glaciated landscapes reveal glacial landforms in extraordinary detail, showing previously mapped landforms in exquisite new detail (for example, end moraines, drumlins, eskers, ice-walled-lake plains etc.). Particularly important are a range of ‘mesoscale’ landforms that are better seen with LiDAR: De Geer moraines, crag-and-tail ridges, low-relief lineations, post-glacial faults, glacial hummocks, and raised shorelines to name a few. A spate of research has come out recently on such features. LiDAR images also have the potential of revealing landforms new to glacier science, of which ‘murtoos’ are an example. But LiDAR also raises the challenge of geomorphic classification. For example, glacial hummocks and glacial hummocky topography are a mesoscale landform that is known for its high variability. This variability, made more dramatic with new LiDAR images, along with the polygenetic origin of landforms called ‘hummocks’ reveals a weakness in our terminology that needs to be acknowledged and dealt with.</p>

The tsunami geomorphology of coastal dunes

An examination of the coastal geomorphology of bays along the Otago coastline, SE New Zealand, has identified a geomorphology consistent with tsunami inundation. A tsunami geomorphology consisting of a number of elements including dune pedestals, hummocky topography, parabolic dune systems, and post-tsunami features resulting from changes to the nearshore sediment budget is discussed. The most prominent features at Blueskin Bay are eroded pedestals although it is speculated that hummocky topography may be present in the bay. Tsunami geomorphology at Long Beach is more comprehensive with a marked association between pedestals and a hummocky topography. A full suite of potential geomorphological features however, is not present at either site. The type of features formed by a tsunami, and the ability to detect and interpret a tsunami geomorphology, hinges on the interaction between five key variables; sand availability, embayment type, nature of the coast, accumulation space, and landward environmental conditions. An appreciation of the geomorphic setting and history of a coast is therefore of fundamental importance when identifying what to look for and where to look for tsunami evidence. It is also important to realise that these features can also be formed by other processes.