Ž . Geomorphology 39 2001 39–51 www.elsevier.nlrlocatergeomorph Late Holocene slackwater deposits on the Nakagawa River, Tochigi Prefecture, Japan A.P. Jones a, ) , H. Shimazu b , T. Oguchi c , M. Okuno d , M. Tokutake e a Department of Geography, UniÕersity of LiÕerpool, Roxby Building, LiÕerpool L69 3BX, UK b Department of Geography, Faculty of Geo-EnÕironmental Science, Rissho UniÕersity, Saitama 360-0194, Japan c Center for Spatial Information Science, UniÕersity of Tokyo, c r o Department of Geography, Faculty of Science, Tokyo 113-0033, Japan d Department of Earth System Science, Fukuoka UniÕersity, Fukuoka 814-0180, Japan e Taisei Kiso Sekkei Co. Ltd., Tokyo 151-0053, Japan Received 2 December 1999; received in revised form 28 June 2000; accepted 16 October 2000 Abstract A continuous succession of slackwater deposits was investigated on the Nakagawa River, Karasuyama Town in Tochigi Prefecture, Japan. Forty-one and 32 flood events were estimated from two sedimentary cores. Minimum sedimentation rate is estimated at 4.6 mmryear and the calculated maximum flood recurrence interval is 14 years. The sedimentation rates are high compared to other published data and are thought to be the key reason as to why these deposits were preserved in Japan, previously considered too humid. High sediment accumulation rates are thought to compensate for any bioturbation activity that would disturb and homogenise the slackwater deposits. This study is important because it presents a new arena for palaeoflood analysis, suggesting that there is potential for slackwater preservation in similar humid settings. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Slackwater deposit; Sediment accumulation rate; Palaeoflood; Japanese rivers 1. Introduction Slackwater deposits have been used, in numerous studies over the past two decades, to estimate the magnitude and frequency of discrete flood events Ž e.g. Kochel and Baker, 1982; Kochel et al., 1982; Partridge and Baker, 1987; O’Connor et al., 1994; Wohl et al., 1994; Kale et al., 1994; Benito et al., ) Corresponding author. Fax: q 44-151-7942866. Ž . E-mail address: alijones@liverpool.ac.uk A.P. Jones . . 1998 . They originate, as their name suggests, through deposition in slackwater areas, protected from the main channel flow. They are typically found at the confluence of main rivers and their Ž tributaries, in bedrock canyons Kochel and Baker, . 1988 . This is particularly true of narrow, deep, entrenched bedrock canyons where small increases in flood discharge are accompanied by large in- creases in flood stage. Geographically, clear slack- water stratigraphies are most common in semiarid Ž areas such as Texas and Arizona e.g. Baker, 1977; . Kochel et al., 1982; Kochel, 1988 . In contrast, such clear stratigraphies are rarely found in humid regions 0169-555Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-555X 01 00050-2