The Floyd River is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Missouri River

Missouri River

The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...

, 112 miles (180.2 km) long, in northwestern Iowa

Iowa

Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It enters the Missouri at Sioux City

Sioux City, Iowa

Sioux City is a city in Plymouth and Woodbury counties in the western part of the U.S. state of Iowa. The population was 82,684 in the 2010 census, a decline from 85,013 in the 2000 census, which makes it currently the fourth largest city in the state....

, and is named for Charles Floyd

Charles Floyd (explorer)

Charles Floyd was a United States explorer, a non-commissioned officer in the U.S. Army, and quartermaster in the Lewis and Clark Expedition. A native of Kentucky, he was a relative of William Clark, an uncle to the politician John Floyd, and a brother to James John Floyd...

, a member of the Lewis and Clark Expedition

Lewis and Clark Expedition

The Lewis and Clark Expedition, or ″Corps of Discovery Expedition" was the first transcontinental expedition to the Pacific Coast by the United States. Commissioned by President Thomas Jefferson and led by two Virginia-born veterans of Indian wars in the Ohio Valley, Meriwether Lewis and William...

.

Course

The Floyd River rises in northwestern O'Brien County

O'Brien County, Iowa

-2010 census:The 2010 census recorded a population of 14,398 in the county, with a population density of . There were 6,649 housing units, of which 6,069 were occupied.-2000 census:...

 near the town of Sanborn

Sanborn, Iowa

As of the census of 2000, there were 1,353 people, 558 households, and 372 families residing in the city. The population density was 747.1 people per square mile . There were 593 housing units at an average density of 327.5 per square mile...

 and flows generally southwestwardly through Sioux

Sioux County, Iowa

-2010 census:The 2010 census recorded a population of 33,704 in the county, with a population density of . There were 12,279 housing units, of which 11,584 were occupied.-2000 census:...

, Plymouth

Plymouth County, Iowa

Plymouth County is a county located in the U.S. state of Iowa. The population was 24,986 in the 2010 census, an increase from 24,849 in the 2000 census. The county seat is Le Mars...

 and Woodbury

Woodbury County, Iowa

-2010 census:The 2010 census recorded a population of 102,172 in the county, with a population density of . There were 41,454 housing units, of which 39,052 were occupied.-2000 census:...

 counties, past the towns of Sheldon

Sheldon, Iowa

Sheldon is a city in O'Brien and Sioux Counties in the U.S. state of Iowa, along the Floyd River. The population was 4,914 at the 2000 census; it is the largest city in O'Brien County.- History and culture :...

, Hospers

Hospers, Iowa

Hospers is a city in Sioux County, Iowa, United States, along the Floyd River. The population was 672 at the 2000 census.-Geography:Hospers is located at ....

, Alton

Alton, Iowa

Alton is a city in Sioux County, Iowa, United States, along the Floyd River. As of the 2000 census, the city population was 1,095.-Geography:Alton is located at ....

, Le Mars

Le Mars, Iowa

Le Mars is a city in and the county seat of Plymouth County, Iowa, United States. The population was 9,237 at the 2000 census. Le Mars is the home of Wells' Dairy, the world's largest producer of ice cream novelties in one location and is the self-proclaimed "Ice Cream Capital of the World". Wells...

, Merill

Merrill, Iowa

Merrill is a city in Plymouth County, Iowa, United States, along the Floyd River. The population was 754 at the 2000 census.- History :Merrill is named for the seventh Governor of Iowa Samuel Merrill. The community was officially recognized on February 27, 1872. and became a incorporated city on...

, and Hinton

Hinton, Iowa

As of the census of 2000, there were 808 people, 303 households, and 226 families residing in the city. The population density was 1,386.1 people per square mile . There were 319 housing units at an average density of 547.2 per square mile...

. At Merrill the Floyd collects its largest tributary, the West Branch Floyd River, which is about 40 mi (65 km) long. The West Branch rises near Boyden

Boyden, Iowa

Boyden is a city in Sioux County, Iowa, United States. The population was 672 at the 2000 census.-Geography:Boyden's longitude and latitude coordinatesin decimal form are 43.190221, -96.003698...

 in northeastern Sioux County and flows generally southward into Plymouth County, past Maurice

Maurice, Iowa

Maurice is a city in Sioux County, Iowa, United States, along the West Branch of the Floyd River. The population was 254 at the 2000 census. It is home to the "Famous Maurice Fire Escape Slide" in the town park.-Geography:...

 and Struble

Struble, Iowa

Struble is a city in Plymouth County, Iowa, United States, along the West Branch of the Floyd River. The population was 85 at the 2000 census.-Geography:Struble is located in Elgin Township, some seven miles north of LeMars, at ....

. The Floyd enters Woodbury County near the Leeds neighborhood of Sioux City.

The Floyd River has come out of its banks on several occasions, causing distastrous flooding in Sioux City in 1892 and 1953. The river has since been the focus of an intensive flood control

Flood control

In communications, flood control is a feature of many communication protocols designed to prevent overwhelming of a destination receiver. Such controls can be implemented either in software or in hardware, and will often request that the message be resent after the receiver has finished...

 project. The Floyd's lower channel through Sioux City has been straightened, channelized, lined with riprap

Riprap

Riprap — also known as rip rap, rubble, shot rock or rock armour or "Rip-rap" — is rock or other material used to armor shorelines, streambeds, bridge abutments, pilings and other shoreline structures against scour, water or ice erosion.It is made from a variety of rock types, commonly granite or...

 and banked by a high earthen levee

Levee

A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

.

The Floyd River is the site of frequent fish kill

Fish kill

The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...

s caused by runoff

Surface runoff

Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

 of massive amounts of animal waste from farm feedlot

Feedlot

A feedlot or feedyard is a type of animal feeding operation which is used in factory farming for finishing livestock, notably beef cattle, but also swine, horses, sheep, turkeys, chickens or ducks, prior to slaughter. Large beef feedlots are called Concentrated Animal Feeding Operations . They...

s into the river.