The Detroit River is about 32 miles long from its head at the Windmill Point Light to its mouth at the Detroit River Light in Lake Erie. The fall in water level from Lake St. Clair to Lake Erie, about three feet. The river is characterized by two distinct reaches. The upper reach extends downstream from Lake St. Clair to the head of Fighting Island, about 13 miles. As water flows out of Lake St. Clair, it divides as it passes Peach (Peche) Island. The channels on both sides of this island are relatively deep, but the main navigation channel from Lake St. Clair lies north of this island. Just below Peach Island lies Belle Isle. The main river channel, the Fleming Channel, runs to the south of this island. The channel north of Belle Isle is divided by the Scott Middle Ground, over which depths vary from 1 to 6 feet. The channels on either side of the Scott Middle Ground are quite deep (19 to 30 feet), but are only used by small craft.
From the foot of Belle Isle to the head of Fighting Island, the channel is generally broad and deep. Its bottom consists of sand and clay and its banks are quite steep. The river, in this reach, averages about 2,400 feet in width and has depths of 35 to 50 feet. The deepest areas are found in the vicinity of the Ambassador Bridge, where the river slightly narrows to a width of about 1,900 feet for a distance of 1-1/2 miles.
The southerly or lower reach of the Detroit River is broad, with several islands and shallow expanses. In the upper part of this reach, the banks rise with a gentle slope and the bottom consists of sand, clay, boulders and rock. In the six mile stretch from just downstream of Fighting Island to the south end of Bois Blanc Island, the bottom is mainly bedrock and boulders. The natural formation of the lower river bed has required very extensive rock excavation and dredging to provide navigation channels of suitable width and depth for large vessels engaged in lake commerce. During high flow conditions, velocities in these channels vary from 2.5 to 5.5 feet per second, depending upon the configuration of specific cross-sections.
At the head of Fighting Island, the river divides into three channels; east and west around the island and an extensive middle ground further to the west. The middle channel, known as the Fighting Island Channel, is the main navigation channel. The channel on the Canadian side of Fighting Island (east) is divided by Grass and Turkey Islands before it rejoins the main channel below Fighting Island. The west-most channel (along the U.S. shore), which was originally narrow and crooked, has been straightened by a cut across the upper end of the middle ground. This channel divides around Grosse Ile. The channel west of Grosse Ile is the Trenton Channel. The other channel rejoins the main (middle) channel at the foot of the middle ground. River depths at the south end of the Trenton Channel are less than 10 feet and do not permit navigation of deep-draft vessels. Turning basins in this channel allow deep-draft vessels to re-navigate into the Detroit River. The Trenton Channel below Gibraltar is divided by Celeron Island.
Downstream of Fighting Island the river is broad and shallow, except in the navigation channel (the Ballards Reef Channel). About 1-3/4 miles below Fighting Island, this channel divides around Stony Island. To the east of Stony Island, the navigation channel splits (around dikes) into the Amherstburg and Livingstone Channels. The Amherstburg Channel, between Bois Blanc Island and the Canadian mainland, accommodates upbound traffic. The Livingstone Channel, west of Bois Blanc Island, accommodates downbound ship traffic. These two channels recombine below Bois Blanc Island as the river enters Lake Erie.
Originally, the best channel for navigation, downstream of Fighting Island, lay along the Canadian shore. However, vessel draft was limited by a rock ledge extending east from Stony Island, at a depth of about 13 feet, known as the Limekiln Crossing. In 1876, the United States began removal of rock; securing depths, by 1886, of 20 feet over a width of 300 feet. From that time, improvement work has been almost continuous. In 1886, work began to widen the Limekiln Crossing Channel to 440 feet. This was completed in 1890. Between 1901 and 1904, this channel was widened to 600 feet.
In 1887, construction began on a bridge between Belle Isle and the United States mainland. This bridge was completed in 1889. In 1915, the superstructure of the bridge was destroyed by fire and was replaced by concrete arches. The bridge piers undoubtedly reduced the flow through the channel west of Belle Isle, but the effect upon the levels above is considered insignificant.
As part of a 21-foot Great Lakes Ship Canal project, dredging began in 1894 to remove shoals from an area extending from the head of Ballards Reef to Limekiln Crossing, for a width of 800 feet and a depth of 21 feet. Also as part of this project, dredging was done to remove a bar at the mouth of the Detroit River (1892-1897). By 1900, improvements had also been made in the Amherstburg Reach and Hackett Reach of the Amherstburg Channel and Grosse Pointe Flats to provide depths of 21 feet.
In 1908, work was begun on the Livingstone Channel, in order to provide a separate downbound channel 300 feet wide and 24 feet deep. The channel was cut across the shallow water east of Stony Island and extended downstream and west of Bois Blanc Island to deep water in Lake Erie. The upper portion, about 6,000 feet in length, was enclosed by cofferdams and dewatered. When work was completed, in 1912, the cofferdams were left as a form of compensation. Openings were made at each end of the cofferdam enclosure, 300 feet in width. The openings were widened to 450 feet in 1915. Between 1920 and 1922, the Livingstone Channel was widened to 450 feet over its entire length. During the same period, the construction of a dike on the west side of the lower part of the channel and the dumping of dredged material, was completed.
Before the construction of the Livingstone Channel, little if any attention was given to the effect of channel improvements upon lake levels. However, all of the material excavated from one part of the river was dumped in other portions. This undoubtedly gave some compensation. There had also been some encroachment on the river by wharfs along the water front, and the extensive filling at the head and foot of Belle Isle, by the City of Detroit. Sherman Moore, with the U.S. Lake Survey District, Corps of Engineers, wrote in 1935 that"....it appears fairly certain that in spite of the large amount of dredging in the interests of navigation, including the breaching of the rock ledge at the Limekiln Crossing, there has been no measurable change in the capacity of the Detroit River as a whole between 1859 and 1932....While the capacity of the river as a whole has been unchanged, the capacity of certain reaches has been slightly increased while that of other reaches has been diminished....the capacity of the reach (from Stony Island to below Bois Blanc Island) has been increased while the capacity of the reach between Windmill Point and Fort Wayne has been reduced by filling above and below Belle Isle, and by encroachment of the dock lines at Detroit."
A 24-foot Navigation Project was begun in 1932. This project required further deepening of the channels in the lower river and some dredging near the head of the river. To further deepen the Livingstone Channel, it was enclosed by a cofferdam from 1932 to 1935. In 1935, the upstream and downstream ends of the cofferdam were removed. The sides were left in place to compensate for the increased depth of the channel. An additional compensating dike, extending westerly from the west dike of the Livingstone Channel towards Sugar Island, was constructed in 1936.
In 1940, the deepening of the Trenton Channel was begun. The project provided for a turning basin 1,700 feet downstream of the lower Grosse Ile Bridge and a 250 feet wide, 21 foot deep channel from the main navigation channel to the turning basin. In 1964, additional dredging was completed to provide for a 300 foot wide, 27 foot deep channel from the main navigation channel to the Upper Grosse Ile Bridge; and for a 300 foot wide, 28 foot deep channel extending about 6,000 feet downstream of the bridge, to and including an upper turning basin 28 feet deep and 15 acres in area, outside the channel limits.
Between 1957 and 1962, dredging was again done in the river, this time to accommodate a 27-foot Navigation Project. The majority of the work was done in the Amherstburg Channel. This work was completed in August 1959. To compensate for the additional channel capacity, two dikes were constructed. One dike was an enlargement of an existing dike at the junction of the Amherstburg/ Livingstone and Ballards Reef Channels. Construction of this dike was started in May 1957 and was completed in August 1959. The dike is along the west side of the Amherstburg Channel and extends 10,000 feet downstream of the Upper Entrance Light. The second dike was built downstream of the lower end of Bois Blanc Island, parallel to and 100 feet west of the Amherstburg Channel. The construction of this dike, 6,200 feet in length, was started in January 1958 and was completed in May 1959.
Water depths in the river vary in accordance with the seasonal levels on Lakes St. Clair and Erie. Fluctuations of several feet, lasting over periods of several hours, can occur as a result of transient meteorologic phenomena. Such fluctuations at the mouth of the Detroit River are produced by high easterly or westerly winds, which cause the water levels to vacillate in Lake Erie. These changes have been as great as eight feet within a five-hour period (April 6, 1979), with a water surface slope of about 14.5 feet from one end of Lake Erie to the other end.
Ice conditions in the Detroit River are considerably different from those in the St. Clair River. An ice bridge, or arch, usually develops in Lake St. Clair, across the head of the Detroit River, upstream of Peach Island. The ice bridge remains stable in the open lake and during periods of subfreezing temperatures, the edge of the ice bridge extends downstream to Peach Island, forming an ice arch on either side of the island. One exception is the broad and shallow passage between Belle Isle and the U.S. mainland. During periods of above freezing temperatures, the ice bridge erodes back into the Lake St. Clair and large sheets of ice begin to drift downstream into the upper Detroit River. If Lake Erie ice is fast or jammed in the lower end of the river, ice back-up results. Occasionally, during a prolonged warm spell, or an early spring breakup on Lake St. Clair, the entire river may fill with ice. The remainder of the upper river normally does not freeze over, due to its narrow channel and swift current.
In the lower river, ice cover develops in the broad and shallow areas adjacent to the lower islands; nevertheless, the main navigation channels, particularly the Livingstone Channel, remain open as long as ice entering the channel can pass into Lake Erie. Ice in western Lake Erie is usually fast, but can shift in large sheets under the influence of prevailing winds. Westerly winds can create large areas of open water downstream of the Livingstone Channel, which can absorb most of the ice moving through the system. Easterly winds blow ice into the lower river and cause jams that can raise upstream levels and hamper navigation. Upstream flooding does not appear to be a serious problem, because the river banks are steep and most of the shoreline development was designed to tolerate the high levels that could result from occasional seiche effects on Lake Erie. Strong easterly winds temporarily raise western Lake Erie levels, which may exceed seven feet above chart datum. This condition has, on rare occasions and for short periods of time, actually reversed the direction of surface flow in the Detroit River. This was documented in 1986 by the GLERL from data recorded at an in-place current meter at the Fort Wayne section. At that time the meter indicated that the direction of flow had turned 180 degrees.