I examine how rising or falling tide can affect the water level of Corte Madera Salt Marsh in this report. The data is from Wednesday (June 19th) and Thursday (June 20th). My hypothesis is that tide and water level have positive relationship. From the result, I learn that the water level and tide have positive relationship. However, when tide changes its direction, the water level is likely to stay or little change.
On June 19th, my classmates and I had field trip for Oceanography Lab (OCN 101) class with Professor Ocean Matt Horrigan. We went to Corte Madera Salt Marsh, which is located 12 miles North of San Francisco, to examine how rising and falling of tide effect on water level in the marsh and channel. My hypothesis is tide and water level of marsh and channel has positive relationship. The rising tide may raise the water level of marsh and falling tide make water level of marsh decrease. Therefore, since our experiment was limited in few hours, the water level of marsh will be changed (up or down) in few centimeters. The location map (M-1) and study area map (M-2) will be attached on next page.
To measure and compare the water level of marsh and channel, the class moved along the levy and placed meter sticks into marsh (B) and opposing channel (A). We had four locations for variable: The T (1), Caution Sign (2), Meris’ Bench (3), and the Point (4). Since the meter sticks were not exactly placed to set ‘0’ as the begging of change, the ‘0’ was adjusted depend on the location. The experiment location started with 1 to 4 and came back from 4 to 1. Therefore, each location has different elapsed time. For example, site 4 (The Point) has shortest time because we put meter sticks and took off without any moving location.
Our data has two tables because it contains data from two classes. First data is from Wednesday 19th (T-1), which is our class and the other data is from Thursday class (T-2), 20th of July. The location and the experiment time period are same for both data tables. The Tables are attached on following page.
The result of T-1 and T-2 is different. T-1 does not have any significant change in water level the greatest change was -5cm/h at 4A. Half of locations do not have any change. On the other hand, only 1 location does not have change in the other group’s table. Most of velocities from T-2 are negative. Therefore, the water level is decreasing. No matter the experiment time is almost same (None of data has difference more than 10 minute For example, in T-1, the time in for 1A is 14:39 pm and in T-2, the time in for 1A is 14:33 pm), the result from each table has large difference. I assume the difference cause by having different tide cycle on both days.
To confirm my assumption, which is ‘each day has different tide cycle,’ I compare our data to Corte Madera tide table. On Wednesday 19th, Corte Madera Creek has first low tide at 3:37 AM and second low tide at 2:57 pm. The first high tide was at 10:05 am and the next high tide was at 9:22 pm. The tidal coefficient was 67 (middle). The maximum high tide recorded in the tide tables for Corte Madera Creek which is of 7.2 ft and a minimum height of -2.0 ft. Therefore, during experiment (2:39 pm first in and 4:01 pm last out), we had second low tide after we put meter stick on 2B but before 3A. Then, the graph shows that the tide started to rise slowly during rest of period. 1B (2:40 – 4:01 pm), 3A (3:01-3:52 pm) and 4B(3:13-3:38 pm) have positive velocity responding to the tide table.
On Thursday, 20th of June, the first low tide was at 4:28 am and the next low tide at 3:54 pm. The first high tide was at 11:12 am and the next high tide was at 10:10 pm. The tidal coefficient was 77 (high). The maximum high tide is of 7.2 ft and a minimum height of -2.0 ft. The fist time in of meter stick was 2:33 pm and the last time out of meter stick was 3:57 pm on Thursday. Therefore, during experiment, the tide was falling toward second lowest tide. Since expect 3B all of result has negative velocity, my hypothesis was correct.
The possible reason why T-1 has more ‘0’ velocity than T-2 is low tide was middle of experiment in the middle of experiment. When tide changes its direction, the water level may stay or have little change.
“2013 Tide Table for Corte Madera Creek, California for fishing,” Tides4Fishing, (July 09), http://www.tides4fishing.com/us/california/corte-madera-creek