This earth cache will require you to visit at both low tide and high tide. Bring a tape measure with you or some other measuring device.
You'll be surprised at the volume of water that enters and leaves The Thames with each change of the tides creating a current known as a tidal stream. It is difficult to measure how much water is in this study area, as water levels are influenced by natural forces. Spring Tides occur 2-3 days after a full moon. Neap tides occur every two weeks, 2-3 days after the moon is in it's first and last quarter. The charted depth of The Thames at Westminster Bridge is 1.9 meters. However, at Spring Tide, it is 6.8 meters deeper and at mean tide, it is 5.6 meters deeper. The tidal range (difference between water levels at low tide and high tide) varies during the month as well. For your purposes, you will be measuring the tidal range on any one day of the month, once at high tide and once at low tide, just to get an appreciation for the vast volume of water that enters our study area due to the tides. You will then consider what detrimental affects these tides can have on the environment.
From the sidewalk measure the distance from the top of the wall to the surface of the river at low tide. Return at high tide and measure it again to determine the tidal effect on water levels. Use the following link to find low/high tide times. http://www.pla.co.uk/Safety/Tide-Tables
Using your GPS, determine how wide The Thames is at this spot. Also determine an approximate length between The Hungerford Bridge and The Westminster Bridge. These are the two bridges on either side of The London eye.
Multiply The Thames width X The Thames Length between the bridges X the change in tide level. This will determine the volume of water that enters/leaves this section of The Thames as a result of each tide change on the particular day that you visited.
Research the weight of water and calculate how much that total volume of water entering/leaving The Thames in this study section on each tide change weighs.
Feel free to use the imperial or metric measurements. It's your choice.
Email me the following answers to log your find:
1. The volume and the weight of the water that flowed into the area today as a result of the changing tide.
2. What problem would this much water movement have on a natural shoreline and what measures have been taken to combat it?
3. What are the oscillating currents called that are created by the tidal change?
4. Other than the shoreline, what else could be affected by them?
5. This section of the river appears to be very straight. However, The Thames meanders throughout the city. If the measures from question #2, were not taken, how would the meandering be affected?
CONGRATULATIONS on the FTF...mbtkz...Feb 25, 2014