What happens when a stream floods?

Floods occur when the discharge of the stream becomes too high to be accommodated in the normal stream channel. When the discharge becomes too high, the stream widens its channel by overtopping its banks and flooding the low-lying areas surrounding the stream. The areas that become flooded are called floodplains.

What happens when a stream flows down?

Deposition by Streams and Rivers When a stream or river slows down, it starts dropping its sediments. Larger sediments are dropped in steep areas. Some smaller sediments can still be carried by a slow moving stream or river. Smaller sediments are dropped as the slope becomes less steep.

Do streams get their water from rain?

Runoff from rainfall or other precipitation supplements the flow of seasonal stream. During dry periods, seasonal streams may not have flowing surface water. Runoff from rainfall is the primary source of water for these streams. Like seasonal streams, they can be found anywhere but are most prevalent in arid areas.

What does water erosion do?

Water erosion is the detachment and removal of soil material by water. The process may be natural or accelerated by human activity. The rate of erosion may be very slow to very rapid, depending on the soil, the local landscape, and weather conditions. Water erosion wears away the earth’s surface.

How does water flow into and out of streams?

Flowing water finds its way downhill initially as small creeks. As small creeks flow downhill they merge to form larger streams and rivers. Rivers eventually end up flowing into the oceans. If water flows to a place that is surrounded by higher land on all sides, a lake will form.

How does heavy rainfall cause flooding?

The most common cause of flooding is prolonged rainfall. If it rains for a long time, the ground will become saturated and the soil will no longer be able to store water leading to increased surface runoff. This leads to a sudden and large increase in the river’s discharge which can result in a flash flood.

Where does stream water come from?

When precipitation falls onto the ground, some water trickles into groundwater, but much of it flows downhill across the surface as runoff and collects into streams. A watershed, or drainage basin, is the area that collects water for a stream.

What is stream flow in hydrology?

Streamflow is the volumetric discharge expressed in volume per unit time (typically cubic feet per second (ft3/s) or cubic meters per second (m3/s)) that takes place in a stream or channel and varies in time and space. From: Flood Forecasting, 2016.

How do streams flow?

A river forms from water moving from a higher elevation to a lower elevation, all due to gravity. Flowing water finds its way downhill initially as small creeks. As small creeks flow downhill they merge to form larger streams and rivers. Rivers eventually end up flowing into the oceans.

What is water erosion called?

The erosion that’s caused by the water runoff from these heavy rainstorms or melting snow is called gully erosion. This type of water erosion creates large cuts in the land that are usually more than one foot deep. The final type of water erosion is called streambank erosion.

How do floods cause erosion?

Increased volumes of runoff can lead to flooding and a higher velocity or flow of the river. Increased flow creates friction along the stream banks and eventually the bank itself begins to erode away and the loose sediment is carried down stream.

What happens when a lot of rain falls on the ground?

When a lot of rain falls in a short period of time, much of the water is unable to soak into the ground. Instead, it runs over the land. Gravity causes the water to flow from higher to lower ground. As the runoff flows, it may pick up loose material on the surface, such as bits of soil and sand.

What happens when it rains too much water?

When a lot of rain falls in a short period of time, much of the water is unable to soak into the ground. Instead, it runs over the land. Gravity causes the water to flow from higher to lower ground. As the runoff flows, it may pick up loose material on the surface, such as bits of soil and sand.

What happens to a stream when it overflows?

A high and fast water flow encourages stream channelization which can then disconnect a stream from its floodplain. If a stream can’t overflow its banks onto a floodplain, then the water from a storm won’t slow down and infiltrate the surrounding soils. This leads to much more water rushing directly into the stream.

What makes a stream flow faster or slower?

The slope of the land over which the water flows is one factor. The steeper the slope, the faster the water flows. Another factor is the amount of water that’s in the stream. Streams with a lot of water flow faster than streams that are nearly dry.