Bed-load yield of the rivers of Kamchatka krai
L.V. KUKSINA
Lomonosov Moscow State University, Moscow, Russia
Keywords: bed load, yield, suspended sediment, N.I. Alekseevskii method, ratio, river order
Abstract
Bed-load yield was estimated for 60 river cross-sections flowing into the Pacific Ocean, the Bering Sea and the Sea of Okhotsk in the Kamchatka krai territory on the basis of N.I. Alekseevskii method developed for bed-load transport assessment by the movement of five types of bottom ridges during floods and low-water periods. For 398 unstudied rivers bed load was assessed by the relationship between specific bed load yield and basin area. Estimates of the specific bed-load yield for the rivers studied show that the highest values are observed in rivers with a relatively small catchment area, often characterized by a mountainous or semi-mountainous type of channel with a pebble-boulder composition of channel sediments. Specific bed-load yield significantly decreases with increasing catchment area and with the transition from mountainous/semi-mountainous to plain sections of rivers. The total mean annual bed load yield is estimated at 18 mln t per year, and it exceeds suspended sediment yield by a factor of 1.5. A spatial analysis of bed load variability is made for the Kamchatka River basin. It was found that bed load is larger in eastern tributaries of the river draining areas of active volcanism in Kamchatka. Variability in bed load along the Kamchatka River shows a decrease in its proportion in the total sediment yield from the source to the mouth due to the channel changes from mountain to plain type. It has been demonstrated that for some mountain rivers with a pebble and pebble-boulder sediment composition, the share in the total sediment yield can approach 100 %. It decreases to 40-70 % in semi-mountain rivers. The share of bed-load material in the total sediment yield reaches its minimum values in large lowland rivers and is about 13-20 %.
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