Fire, storms, and erosional events in the Idaho batholith

Abstract

Abstract:In late December 1996, the South Fork Payette River basin in west-central Idaho experienced a prolonged storm that culminated on January 1, 1997, with intense rain on melting snow that triggered slide failures, producing debris flows and sediment-charged floods. Failures occurred in saturated, cohesionless, grussy colluvium derived from weathered Idaho batholith granitic rocks. Many failures along the South Fork Payette River originated in ponderosa pine forests burned in the 1989 stand-replacing Lowman fire. An example is the 0Ð49 km 2 'Jughead' Creek basin, where a single large colluvial failure produced almost 40% of the total volume eroded from the basin and generated a massive and rapid debris flow. Failures also occurred in steep, unburned, and unforested drainages such as Hopkins Creek. In this south-facing 0Ð58 km 2 basin, 15 colluvial hollows failed, but no single failure produced more than 10% of the total eroded volume. Sediment transport in Hopkins Creek occurred by prolonged sediment-charged sheetflooding. Despite vegetation differences, sediment yields from the geomorphically similar Hopkins Creek (¾42 000 Mg km 2 ) and Jughead Creek (¾44 000 Mg km 2 ) basins were quite similar. These 1997 erosion events are equivalent to several thousand years of sediment yield at low rates (2Ð7-30 Mg km 2 year 1 ) measured by short-term sediment trapping and gauging in Idaho batholith watersheds. If similar large events were solely responsible for sediment export, recurrence intervals (RIs) of several hundred years would account for higher sediment yields averaged over ¾10 4 year from Idaho batholith watersheds. Dating of small fire-induced sheetflooding events in an early Holocene tributary junction fan of Jughead Creek indicates that frequent small sedimentation events (RI ³ 33-80 year) occurred between 7400 and 6600 cal year BP, with an average yield not greatly exceeding 16 Mg km 2 year 1 . Compared with the Holocene average, erosion rates during that 800 year period were unusually low, suggesting that sediment yields have not been constant over time, and that climatic variations and related fire regime changes may exert a strong influence on the probability of major erosional events.

Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

“…The results of Meyer et al (1995), discussed by Meyer and Pierce (2003), suggest an anti-correlation with Bond cycles and also a response to century-scale events such as the MWP and the Little Ice Age. Meyer and Pierce (2003) also compared the Yellowstone results to those from Idaho (Meyer et al 2001). In this study, we note that the Bear Flat record shows evidence for fires during the MWP, but earlier fires appear to show a comparable millennial-scale trend to the Yellowstone results.…”

“…in Yellowstone (Meyer et al 1995;Millspaugh et al 2000), Idaho (Meyer et al 2001), Oregon (Long et al 1998), southwestern BC (Gavin et al 2003b;Hallett et al 2003a;Lertzman et al 2002), and southeastern BC (Hallett and Walker 2000;Hallett et al 2003b). This signal appears less marked in the tropics (Horn and Sanford 1992;Turcq et al 1998) and in other mid-latitude regimes, such as in eastern Canada (Carcaillet et al 2001) and New Zealand (Molloy et al 1963).…”

“…The long-term record of forest-fire history has been studied in a number of regions (Meyer et al 1995(Meyer et al , 2001Cwynar 1987;Long et al 1998;Hallett et al 2003a,b;Millspaugh et al 2000;Horn and Sanford 1992;Turcq et al 1998;Lertzman et al 2002;Hallett and Walker 2000;Pierce et al 2004) of the world, but there is little information on fire history in more northerly regions of Canada. There are basically 2 kinds of studies: 1) direct measurement of charcoal found in alluvial and colluvial deposits (e.g.…”

“…There are basically 2 kinds of studies: 1) direct measurement of charcoal found in alluvial and colluvial deposits (e.g. Meyer et al 1995Meyer et al , 2001Lertzman et al 2002;Pierce et al 2004); and 2) studies of the charcoal record found in lake sediments (e.g. Long et al 1998;Millspaugh et al 2000).…”

Climatic controls on fire-induced sediment pulses in Yellowstone National Park and central Idaho: a long-term perspective

“…Over periods of several years, impacts along larger streams may range from minor and transient loading with fine sediment to major aggradation of gravel (e.g., Benda et al, 1998). Persistent alteration of channel structure may occur through addition of large woody debris and boulders that remain immobile for centuries or more (e.g., Minshall et al, 1997;Meyer et al, 2001).…”