HISTORIC CHANNEL CHANGES IN THE MUSKEGON RIVER, NORTH-CENTRAL MICHIGAN, USA

The Muskegon River is the second largest river system in Michigan. It originates in the north-central part of Lower Michigan at Houghton Lake and drains an area of 6,086 km² as it flows southwest toward Lake Michigan. Prior research in the basin suggests a complex late Pleistocene and Holocene history, with four alluvial surfaces. In some parts of the system, evidence suggests that the system has been actively meandering in the late Holocene, resulting in numerous abandoned meanders and oxbow lakes. The basin was extensively logged between 1837 and 1910 and the river was used to transport lumber to mills in the area.

This study assesses the extent of meandering over the streams entire length during the historic record by comparing stream patterns from the initial land survey in 1836 with aerial photos acquired in 1938 and 2012. The research focuses on the following questions: (1) What is the nature of changes between the three sample times? (2) What is the extent of change in channel width throughout the system from the initial survey to the present? (3)What are the key variables that may have caused channel changes? To assess these questions a combination of field and laboratory analyses were conducted. River positions at each time period were georectified in ArcGIS10 for comparative purposes. The stream was surveyed by kayak during the summer of 2013 in order to collect modern width measurements along section lines and to analyze channel changes since the initial land survey.

Results indicate that numerous changes have occurred in the Muskegon River in the period of record. The stream appears to have narrowed in the lower part of the system since 1836, whereas it changed little in the upper part. Numerous migrating cutbanks and cutoff meanders were found in the upper half of the system, where the channel slope is consistently low (averaging 0.25 m per km) and sinuosity is high (~ 1.8 - 2.6). The position of the channel in this reach changed the most between 1836 and 1938. The time of greatest change correlates well with Michigan’s intensive logging era. We hypothesize that channel narrowing in the lower reaches is related to devegetated bank slopes and tributary systems that increase sediment yields. Slowing of meander movement in the upper reaches within the past 74 years may be related to increased bank stabilization due to revegetation.