The Force Of Moving Water
- WORK AND ENERGY:A river 's water has energy.Energy is the ability to do work. There are two kinds of energy. Potential energy and kinetic energy.
- Potential energy is that is stored and waiting to be used later. The Merrimack's water begins with potential energy because of their position above sea level.
- Kinetic energy is the energy an object has due to its motion.
- As gravity pulls water down a slope, the water's potential energy changes to kinetic energy that can do work.
- When energy does work it is transferred from one object to another. A river, moving water does have effects though. A river is always moving sediment from mountains to the sea. At the same time, river is also eroding its banks and valley.
- HOW WATER ERODES:In the process of water erosion, water picks up and moves sediment. Sediment includes soil, rock, clay, and clay. Sediment can enter rivers or streams in a number of ways. Most sediment sediment washes or falls into a river as a result of mass movement and runoff. Other sediment erodes from the bottom or sides of the river. Wind may also drop sediment into the water.
- Abrasion is another process by which a river obtains sediment. Abrasion is the wearing away of rock by a grinding action. Abrasion occurs when particles of sediment in flowing water bump into the streambed again and again. Abrasion grinds down sediment particles. For example, boulders become smaller as they are moved down a streambed. Sediments also grind and chip away at the rock of the streambed, deepening and widening the streams channel.
- The amount of sediment that a river carries is its load. Gravity and force of the moving water cause the sediment load to move downstream. Most large sediment falls to the bottom and moves by rolling and sliding. Fast-moving water actually lifts sand and other, smaller sediment and carries it downstream. Water dissolves some sediment completely. The river carries theses dissolved sediments in solution.
- EROSION & SEDIMENT LOAD:The power of a river to cause erosion and carry sediment depends on several factors. A river's slope, volume of flow, and shape of its stream bed all affect how fast the river flows and how much sediment it can erode. A fast flowing river carries more and larger particles of sediment. When a river slows down, it drops its sediment load. The larger particles of sediment are deposited first.
- SLOPE:Usually, if a river's slope increases, the water's speed also increases. A river's slope is the amount the river drops toward sea level over a given distance. If a river's speed increase, its sediment load and power to erode may increase. But other factors are also important in determining how much sediment the river erodes and carries.
- VOLUME OF FLOW: A river's flow is the volume of water that moves past a point on the river in a given time. As more water flows through a river, its speed increases. During a flood, the increased volume of water helps the river to cut more deeply into its banks and bed. When a river floods, its power to erode may increase by a hundredfold. A flooding river can carry huge amounts of sand, soil, and other sediments. It may move giant boulders as is they were pebbles.
- STREAMBED SHAPE: A streambed's shape affects the amount of friction between the water and the streambed. Friction is the force that opposes the motion of one surface as it moves across another surface. Friction, in turn, affects a river's speed. Where a river is deep, less water comes in contact with the streambed. The reduced friction allows the river to flow faster. In a shallow river, much of the water comes in contact with the streambed. So this means that friction increases, reducing the river's speed.
- A streambed is often full of boulders and other obstacles. This roughness prevents the water from flowing smoothly. Roughness then increases the friction and decreases the river's speed. Instead of moving downstream, the water moves every which way in the type of movement called turbulence.