Special Sessions
Sponsored by the Geomorphology Specialty Group
Association of American Geographers 103rd Annual Meeting
San Francisco, California, April 17-21.

Geomorphology Specialty Group Graduate Student Paper Competition III

Paper Session 2439
Wednesday, 4/18/07, from 1:00 PM - 2:40 PM

Sponsorship(s):

Geomorphology Specialty Group

Organizer(s):

Michael Craghan - Middle Atlantic Center for Geog. & Envt. Studies

Chair(s):

Michael Craghan - Middle Atlantic Center for Geog. & Envt. Studies

Abstract(s):

• 1:00 PM Author(s):
  *Stacey Armstrong - Missouri State University
  

  Abstract Title: Human Transformation of a Karst Catchment in Springfield, Missouri.

  
  

  The Ward Branch Watershed on the southern edge of Springfield, Missouri has experienced rapid urbanization over the past decades. During this period one of its tributaries (2 km²) has encountered severe erosion and flooding causing concern by local property owners. Evidence for both stability and disturbance presently exists in the channel system. This study examines the influence of land use and related drainage network changes on stream morphology and stability in an urbanized Ozark tributary. Historical analysis is based on a government land ordinance survey in 1838 and historical aerial photography for 1936, 1953, 1975, 1982, 1990, 1996 and 2005. Field methods included using a total station, GIS and differential GPS to collect a detailed longitudinal profile, cross-sectional profiles, pebble counts and fluvial disturbance indicators. In addition, interviews with local residents are used to provide personal accounts of geomorphic changes. Land use analysis from 1936-2005 indicates that the landscape has been transformed from pasture to urban. Preliminary results indicate that the upper portion of the catchment has been de-coupled from the middle and lower reaches by artificial means. Channel head-cutting in the middle reach is releasing sediment and destabilizing the channel. However, bedrock control limits the response of the lower reaches except where sedimentation is occurring when slope breaks at the confluence with the Ward Branch. Human actions increase the resistance of the channel to erosion through landscaping, sediment grading and local grade controls. A channel evolution model for the catchment is proposed and its implications for management discussed.

  Keywords: environmental history, urbanization, geomorphic instability, and land use

  
  
• 1:20 PM Author(s):
  *Deborah J Belden - Department of Geography, University of Montana
  Ulrich Kamp - Department of Geography, University of Montana
  Yeong Bae Seong - Department of Geology, University of Cincinnati
  Lewis A. Owen - Department of Geology, University of Cincinnati
  

  Abstract Title: Geomorphological Mapping of the Shigar and Braldu Valleys, Central Karakoram, Pakistan, Using GIS and Remote Sensing Techniques.

  
  

  The high Karakoram Himalayas is a region of immense topographic relief whose origin is currently not well understood. K2 is uplifting at 2-6mm a-1, however recent denudation is thought to be due mainly to surface processes, not tectonic unloading. Geomorphological mapping assists in evaluating the polygenetic role of glaciation, mass movement denudation, and fluvial erosion in landscape development and uplift. A series of twelve geomorphological maps 1:100,000 covering the Shigar and Braldu valleys up to K2 were produced using field mapping and photography, GPS measurements, and a digital elevation model generated from ASTER imagery. Landscape and morphometric analysis were performed using GIS software. The landforms are described in relation to geology, geomorphological processes, and altitudinal zones. Case studies of special locations include, for instance, flash flood deposits, active landslide areas, a sackung, and rock avalanches. Quantifying of landform types helps to understand the dominance of single geomorphological processes. Three distinct altitudinal zones could be identified, and each has a dominate erosion/deposition process and moisture pattern. These zones are: (1) the upper zone, above 6000 m is the zone of perennial glacier accumulation and avalanching; (2) the middle zone from 3000-6000 m where active and former glacial processes, freeze-thaw cycles, and fluvial erosion dominate; (3) the lower zone below 3000 m with sub-montane and semi-arid conditions where alluvial fans, landslides, and breakout flood deposits dominate the landscape. This is the first complete geomorphological map series of the area which provides important insight into the nature of topographic evolution.

  Keywords: geomorphology, Karakoram, GIS, glacial, landforms, remote sensing

  
  
• 1:40 PM Author(s):
  *Mark A Gossard - Missouri State University
  

  Abstract Title: Sediment budget approach to evaluate urban-related instability in an Ozark Stream.

  
  

  Sediment load variations can cause channel instability in gravel bed rivers. Accelerated gravel sediment inputs due to land use-related disturbances have been shown to cause channel and bank instability in Ozarks streams. Ward Branch is a heavily urbanized watershed in Springfield, Missouri for which restoration measures are planned. This study aims to use a sediment budget approach to understand the sources and transport patterns of bed load in a particularly unstable 300 meter long "disturbance" reach along Ward Branch where bank erosion and channel incision is releasing excess gravel to the stream. Urbanization has increased the 2-year flood peak by more than three times the presettlement condition. Channel form and erosion/deposition were monitored over a 12 month period. The methods used in this study are (i) repeated cross-section and longitudinal surveys of the channel, (ii) scour chains and bank erosion pins, (iii) pebble counts and sieving of both the bank and bed materials, and (iv) painted tracers to monitor bedload movement. Rainfall records and flood peaks are also being monitored. Results of the tracer experiments showed that during three bankfull floods and one larger event, the D25 moved 25 meters, D40 moved 15 meters, D50 moved 20 meters, D84 moved 16 meters, D90 moved 12 meters, and the D95 moved 7 meters on average with an overall recovery rate of 34%. Results from this study will be used to plan bed and bank stabilization measures and understand channel storage and mobility dynamics of Ward Branch.

  Keywords: Fluvial Geomorphology, sediment transport, urban stream

  
  

Session Description: 3rd of 3 sessions for the Geomorphology S.G. student paper competition.