s2ary
09-10-2007, 06:45 PM
Tidal Channel Development
• Properly spaced tidal channels are a constant. This is because the rate of erosion is equal to the rate of sediment deposition. If the spacing between channels is too close the flow of water in each channel is slow causing the channel to quickly accumulate sediments. If there are too few channels sulfur toxicity increases and adversely impacts salt marsh primary production.
• Most natural tide channels and rills are developed early in a marshes life, in the mud flat or the early low marsh stages prior to the development of the high marsh.
• The volume and velocity of tidal waters flowing through a channel is entirely dependent on the channels watershed area. This volume and velocity of the flow maintains a channel’s size by preventing sediments from falling out of the water column or by eroding the edges of the channel to make it wider.
• Tidal channels erode at the same rate that they accumulate sediments. An established channel is in equilibrium with the size of its watershed. This means that the daily tide cycle cleans out the new sediments that fall into the channel, but just enough for the required volume of water to flood the watershed in the time allowed by a tide cycle.
Channels are the respiratory system of a salt marsh. Marshes breathe in salt water in order to survive. Any blockages to its channel system is like a lung cancer preventing salt water from entering into the marsh and allowing fresher water to persist and reduce the marsh’s function. Remember it is a salt marsh that is 4 times more productive than a corn field, not a brackish marsh or a fresh marsh. Also fish and juvenile crabs, shrimp, and lobsters migrate into the smaller channels and rills to hide from the predators in the main channels. It is vital to our near shore ecology that our marshes function as productively as possible to help rebuild our dwindling fisheries. Since the industrial revolution we have lost half of our nation’s salt marshes, this has a negative impact on all fisheries from cod and flounder to clams and lobsters.
• Properly spaced tidal channels are a constant. This is because the rate of erosion is equal to the rate of sediment deposition. If the spacing between channels is too close the flow of water in each channel is slow causing the channel to quickly accumulate sediments. If there are too few channels sulfur toxicity increases and adversely impacts salt marsh primary production.
• Most natural tide channels and rills are developed early in a marshes life, in the mud flat or the early low marsh stages prior to the development of the high marsh.
• The volume and velocity of tidal waters flowing through a channel is entirely dependent on the channels watershed area. This volume and velocity of the flow maintains a channel’s size by preventing sediments from falling out of the water column or by eroding the edges of the channel to make it wider.
• Tidal channels erode at the same rate that they accumulate sediments. An established channel is in equilibrium with the size of its watershed. This means that the daily tide cycle cleans out the new sediments that fall into the channel, but just enough for the required volume of water to flood the watershed in the time allowed by a tide cycle.
Channels are the respiratory system of a salt marsh. Marshes breathe in salt water in order to survive. Any blockages to its channel system is like a lung cancer preventing salt water from entering into the marsh and allowing fresher water to persist and reduce the marsh’s function. Remember it is a salt marsh that is 4 times more productive than a corn field, not a brackish marsh or a fresh marsh. Also fish and juvenile crabs, shrimp, and lobsters migrate into the smaller channels and rills to hide from the predators in the main channels. It is vital to our near shore ecology that our marshes function as productively as possible to help rebuild our dwindling fisheries. Since the industrial revolution we have lost half of our nation’s salt marshes, this has a negative impact on all fisheries from cod and flounder to clams and lobsters.