Effect Of Glacial Isostatic Adjustment On Rivers And Drainage Basins In The Red River Valley, North Dakota And Minnesota, U.s.a

• Main Author: York, Benjamin Charles
• Format: Text
• Language: unknown
• Published: UND Scholarly Commons 2017
• Subjects: Asymmetry Factor; Paleo-channel; Transverse Topographic Symmetry Factor; Watershed Change; Glacial Lake; Ice Sheet
• Online Access: https://commons.und.edu/theses/2154; https://commons.und.edu/cgi/viewcontent.cgi?article=3155&context=theses

This thesis investigates the relationship between glacial isostatic adjustment and watershed asymmetry of tributaries in the Red River Valley, North Dakota, U.S.A. After the draining of glacial Lake Agassiz, drainage networks began to develop and were affected by isostatic adjustment. This adjustment began after the receding of the Laurentide Ice Sheet and is still occurring today, but on a lesser degree. Adjustment in the Red River Valley, which has varied since the ice sheet retreated, is determined from differences in the elevation of the horizontally deposited beach ridges which are the ancestral beaches of glacial Lake Agassiz. The Red River Valley is currently experiencing one to four mm of uplift per year. Rivers in the Red River Valley are constantly under continental scale tectonic forces. Little work has been conducted regarding the effect of isostatic adjustment on the pattern of post-glacial rivers and watersheds in the Red River Valley in its entirety. Isostatic adjustment is greatest in the northern Red River Valley where the ice was thickest, which has resulted in greater asymmetry in the watersheds farther north in the valley. The purpose of this thesis is to determine if watersheds of Red River tributaries within the former glacial Lake Agassiz basin are asymmetric. The study further documented if asymmetry is the result of 1) changing watershed boundary; 2) a shifting river channel position; or 3) a combination of both a changing watershed boundary and a shifting river channel. Symmetry of each watershed was determined by comparing the following landscape measurements: Transverse Topographic Symmetry Factor (TTSF), Asymmetry Factor (AF), and the total net change in area between pre-adjustment watersheds and current watersheds. Along with the measurements listed above, paleo-channels were identified in the Red River Valley to determine if there has been a uniform shift in drainage between Lake Agassiz stages and isostatic adjustment. Twelve of the sixteen watersheds analyzed in this thesis have ...