Seiches and the slide/seiche dynamics; subcritical and supercritical subaquous mass flows and their deposits. Examples from Swiss Lakes

Swiss Journal of Geosciences

Table 1 The seiche/slide energy ratio of two events in Lake Lucerne and in Lake Geneva have been used to estimate the seiche amplitudes, see Chapter 5; italics indicate input data

Lake Geneva: f = 4.0	mean fall height of slides [m]	lake area [m²]	slide volume [m³]	E_slide: slide energy [J]	E_seiche: seiche energy [J]	energy ratio E_seiche/E_slide	seiche amplitude in the lake [m]	maximum amplitude at Geneva [m]
slide density = 1400 [kg m^–3] ^0.19 = 0.75*/ f	mean fall height of slides [m]	lake area [m²]	slide volume [m³]	E_slide: slide energy [J]	E_seiche: seiche energy [J]	energy ratio E_seiche/E_slide	seiche amplitude in the lake [m]	maximum amplitude at Geneva [m]
Lake Geneva 563 CE	150	5.82·10⁸	2.5·10⁸	1.5E + 14	8.5E + 12	5.7%	2.42	~ 10
Lake Geneva 1584 CE	150	5.82·10⁸	1.5·10⁶	9.0E + 11	5.1E + 10	5.7%	^*0.19	0.75
Lake Lucerne 1601 CE	90	1.10·10⁸	8.0·10⁷	2.9E + 13	9.7E + 11	3.4%	1.88
Lake Lucerne 1687 CE	100	1.10·10⁸	1.0·10⁷	4.0E + 12	1.3E + 11	3.4%	0.70

The forecast seiche amplitude of the 1601 CE event, 1.88 m, is in the estimated range of 1–2 m (Schnellmann, 2004; Siegenthaler et al., 1987). The same procedure leads to an amplitude of 2.42 m, respectively 10 m at Geneva for the 563 CE event. f figures the increase of the seiche amplitude at Geneva shown on February 12, 1950, and on July 28, 1950, due to the funnel-shaped “Petit Lac”; it must be noted, that the values in the last column are independent on f. The much larger energy ratio in Lake Geneva as compared with Lake Lucerne is expected due to the complicated basin geometry of the latter. The 563 CE seiche–amplitude at Lausanne is estimated to be around 1 m for an expected one–node seiche and is much less compared than the 13 m tsunami simulation (Kremer et al., 2012). Such a large event would have been probably mentioned by the bishop of the diocese Lausanne