Title

Historic Landslide Dams along the Upper Indus River, Northern Pakistan

Abstract

A significant number of landslides have occurred along the upper Indus River which resulted in temporary landslide dams. All of these debris dams eventually breach, often causing catastrophic flooding downstream. Remote sensing data can aid in the recognition of many of these features in otherwise inaccessible areas. Regional level landslide inventory maps have recently been prepared, which also show the locations of historic landslide dams. The research reported in this paper was a reconnaissance-level study, aimed at identifying those slides and rock avalanches that are or were more than 500-m long, crossing at least five adjacent contours. Representative examples of the various types of landslides were evaluated using topographic expression, aided by field reconnaissance and literature review. Many of the landslide features described in the study area exceed an entrained debris volume of 10 million m3, which are often described as mega landslides like the Gol-Gone, Satpara, and Katzarah rockslide dams. Cross canyon profiles were also prepared of selected landslides to estimate the likely block kinematics controlling the slopes failure, using the three-dimensional analyst extension of common computer software. The majority of the historic mega landslide events appear to be seismically triggered. The research reported in this paper suggests that the highest concentration of landslide dams were observed in the tectonically active Nanga Perbat Haramosh Massif region, where the river flows through narrow gorges, and/or where active thrust faults cross the river. Most of these features appear to be structurally controlled, translating along suites of planar preexisting discontinuities, such as bedding, jointing, foliation, lithologic contacts, shear zones, or faults. These features often form landslide dams if they empty into perennial river channels and often leave telltale signs of their short-lived existence. These signs include elevated stream terraces, lacustrine deposits (within and upstream of the temporary blockages), local sediment fans which form about the margins of short-lived reservoirs, deeply incised gorges, and scattered outbreak flood debris along the flanks of the river channel, often blocking side canyon tributaries. If infrastructure, such as highways, pipelines, or transmission lines were to be constructed into the study area, the landslide features should merit additional study and field verification to ascertain the validity of the interpreted features.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Bedrock Incision; Landslide Dam; Landslide Inventory Map; Lithology; Remote Sensing; Debris; Faulting; Floods; Reservoirs (Water); Field Verifications; Lacustrine Deposits; Rivers; Canyon; Cognition; Flood Deposit; Inventory; Gilgit-Baltistan; Haramosh; Indus River; Karakoram; Pakistan

Geographic Coverage

Pakistan

International Standard Serial Number (ISSN)

15276988

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2015 American Society of Civil Engineers (ASCE), All rights reserved.

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