630 SEDIMENTARY PROCESSES/Catastrophic Floods Figure Space and time domain for flood producing hydroclimatological conditions and flooding After Hirschboeck (1988) Flood hydroclimatology In: Baker VR, Kochel RC, and Patton PC (eds.) Flood Geomorphology, pp 27 49, London: Wiley; and O’Connor et al (2002) The geology and geography of floods Water Science and Application 5: 359 385 Figure Envelope curve for maximum discharge generation in relation to catchment area After Hirschboeck KK (1987) Cata strophic flooding and atmospheric circulation anomolies In: Mayer LD and Nasch D (eds.) Catastrophic Flooding pp 23 56 Allen & Unwin river systems Within the northern hemisphere, northward draining rivers are particularly prone to ice-jams as the spring melt is initiated within the catchment headwaters before the lower reaches have thawed Within glaciated catchments, ice-cliff or subglacial tunnel collapse can temporarily dam meltwater rivers with a breccia of ice blocks Damming commonly lasts only for periods of up to one hour, as meltwater flows are easily able to penetrate, float, and bulldoze