MAHONING RIVER
The Mahoning River is a river located in northeastern Ohio and a small portion of western Pennsylvania. Three major tributaries make the Mahoning River. West Branch of the Mahoning, Eagle Creek, & Mosquito Lake/Creek. Flowing primarily through several Ohio counties, it then crosses the state line into Pennsylvania before joining with the Shenango River to form the Beaver River. The Mahoning River drops from 1,296 feet at the headwaters near Winona to 761 feet at the outfall near Mahoningtown. It is part of the Ohio River watershed. After the river leaves Mahoning County, it flows south into the Ohio River and the Mississippi River, eventually entering the Gulf of Mexico.
What Happens When A River Floods?
When a river floods, the water rises over its banks and flows out onto the surrounding land. Sediment (composed of clay, sand, and silt) filled floodwater is deposited on the land adjacent to the river, known as a floodplain. This deposited sediment left behind is called an overbank deposit.
Flooding History
The Mahoning river is susceptible to frequent flooding during high rain events. A days long flood lasted almost continuously from March 23 to March 26, 1913. Residents of the area were without water. Damage reached to communities throughout the area, such as Leavittsburg and Lowellville. Losses to the busy industrial area in the region reached the millions of dollars. Flood waters nearly reached the roofs of Republic Steel's plant. Some damaged bridges collapsed. Several water control infrastructure projects followed: The Lake Milton dam was built from 1913 to 1917.
Another dramatic flooding event started when three days of torrential rain fell in July 2003, resulting in such high volume that the river changed its course in Leavittsburg, flooding and destroying nearly 100 homes. For much of the upper half of the river, the land is relatively flat with minimal relief to confine the river making it prone to change courses during high-water events. Around Youngstown, the river valley becomes much more pronounced and the river is more constrained, although there is still room for localized avulsions.
What is a floodplain?
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge. The soils usually consist of clays, silts, sands, and gravels deposited during floods.
Most floodplains are formed by deposition on the inside of river meanders and by overbank flow. Wherever the river meanders, the flowing water erodes the river bank on the outside of the meander, while sediments are simultaneously deposited in a point bar on the inside of the meander. This is described as lateral accretion, since the deposition builds the point bar laterally into the river channel. Erosion on the outside of the meander usually closely balances deposition on the inside of the meander, so that the channel shifts in the direction of the meander without changing significantly in width. The point bar is built up to a level very close to that of the river banks. Significant net erosion of sediments occurs only when the meander cuts into higher ground. The overall effect is that, as the river meanders, it creates a level flood plain composed mostly of point bar deposits. The rate at which the channel shifts varies greatly. Floodplains can form around rivers of any kind or size. Even relatively straight stretches of river are found to be capable of producing floodplains. Repeated flooding eventually builds up an alluvial ridge, whose natural levees and abandoned meander loops may stand well above most of the floodplain.
QUESTIONS/TASKS:
1. Look at the current depth of the water at the time of your visit. How much higher would it need to get in order for it to flow over the bank at this spot?
2. Look around the bank at this location. What indication(s) if any do you see of past flooding? What type of sediments do you see along the bank of the river?
3. Do you see any indication(s) of bank erosion due to flooding?
4. Are there any noticeable erosion control methods in the immediate area?
5. To prove that you were here, please post a picture of yourself or your GPS with the river in the background. Any other photos of the area are also greatly appreciated.