Channel Initiation

The contribution of few days ago Where do channels begin ? looks to channels' forming processes. The scientific debate has another side which regards channels network extraction.

A recent paper by Orlandini et al. (2011), whose results where also presented at CATHY meeting last January, presents a concise but nice introduction to the topic, and a few results based on works made in the Dolomites. A parallel introduction can be found in my slides.

Certainly Orlandini and Moretti have the merit to have produced the most cleaned methods to produce channels delineation (all papers cited below), and in parallel, proper methods for estimating the upslope contributing areas of any point in a catchment. This is an essential ingredient of the whole story of proper watershed (and drainage directions) delineation and we implemented most of their work (not all of it unfortunately) in JGrass. The rest is kind of an epiphenomenon.

Reference

Orlandini, S., and G. Moretti (2009a), Determination of surface flow paths from gridded elevation data, Water Resour. Res., 45, W03417, doi:10.1029/2008WR007099.

Orlandini, S., and G. Moretti (2009b), Comment on ‘‘Global search algo- rithm for nondispersive flow path extraction’’ by Kyungrock Paik, J. Geophys. Res., 114, F04004, doi:10.1029/2008JF001193.

Orlandini, S., Tarolli, P., Moretti, G., Dalla Fontana, G. (2011). On the prediction of channel heads in a complex alpine terrain using gridded elevation data, Water Resources Research, 47, W02538, doi:10.1029/2010WR009648

Where do channels begin ?

It is the title of a famous paper by David Montgomery and Bill Dietrich about channel initiation which appeared in Nature, in 1988, and was followed by a subsequent paper (in 1994 on Water Resources Research): and BTW by many others in the following years to confirm, and using their findings.

So we know much more than then about. However, those pioneering contribution, did refer to what happens in sloped but hilly environments, of Oregon and California. What about the Alps ?

Recent work by Paolo Tarolli brought some quantitative light on the issue. He presented his work at last January Cathy meeting that can be summarized as follows:

-the availability of very detailed laser scanner of topography allows a great opportunity to use objective methods to single out channels' head.
- in a region of the Italian Alps (Dolomites) were surveyed at least two main processes that drive channel initiation: i) channel heads formed essentially by surface runoff (mass wasting, in form of debris flows or "more traditional" erosion), ii) and areas where geology and groundwater seeping upward exercise important controls on channel initiation.
- Wavelet analysis allows to smooth the topography the right way to use in sequence "curvatures" for channels head initiation.

I hope it will not pass to much time before we can bring these tools inside our jgrasstools.

For who is interested, relevant papers are listed below:

References

David R. Montgomery & William E. Dietrich,Where do channels begin? , Nature 336, 232 - 234 (17 November 1988); doi:10.1038/336232a0

MONTGOMERY and DIETRICH. Source Areas, Drainage Density, and Channel Initiation . Water Resour. Res. (1989) vol. 25 (8) pp. 1907-1918

Orlandini, S., Tarolli, P., Moretti, G., Dalla Fontana, G. (2011). On the prediction of channel heads in a complex alpine terrain using gridded elevation data, Water Resources Research, 47, W02538, doi:10.1029/2010WR009648

Passalacqua, P., Tarolli, P., Foufoula-Georgiou, E. (2010). Testing space-scale methodologies for automatic geomorphic feature extraction from LiDAR in a complex mountainous landscape, Water Resources Research, 46, W11535, ISSN: 0043-1397, doi:10.1029/2009WR008812.

Pirotti and Tarolli. Suitability of LiDAR point density and derived landform curvature maps for channel network extraction. Hydrol. Process. (2010) vol. 24 (9) pp. 1187-1197

Sofia, G., Tarolli, P., Cazorzi, F., Dalla Fontana, G. (under review). Channel heads and channel network identification from high-Resolution DTM: a statistical approach, Hydrol. Earth Syst. Sci., ISSN: 1027-5606.

Tarolli, P., Dalla Fontana, G. (2009). Hillslope-to-valley transition morphology: new opportunities from high resolution DTMs, Geomorphology, 113, 47-56, doi:10.1016/j.geomorph.2009.02.006