Tidal Streams Theory

Question 1

Flood tide

Answer 1

Incoming, max flood

Question 2

Ebb tide

Answer 2

Outgoing, max ebb

Question 3

Slackwater

Answer 3

Nil tidal flow

Question 4

Rectilinear tidal stream

Answer 4

Up and down (north and south)

Happens usually in channels or harbours

Question 5

Rotary tide

Answer 5

Happened usually in open water

Has a cycle of 24 hours and 50 minutes

Question 6

Rotary tides flow continually through ___°
Rotary tides do not have any __________.
Rotary tides are caused by ______ ________.

Answer 6

360°
Slackwater
Earths rotation

Question 7

Tidal race

Answer 7

Incredibly strong stream. Caused by the diversion of two bodies causing a constriction of water flow and a high pressure.

Question 8

Tidal streams (TS)

Answer 8

Periodic horizontal reversing movements of the water accompanying the rising and falling of tides.

Question 9

Currents

Answer 9

Non tidal movement
May flow steadily at all depths
May have horizontal and vertical components

Question 10

What is a datum

Answer 10

A reference which measurements are made from

Question 11

Chart datum

Answer 11

Defined as the level which the tide will not frequently fall below.
Usually at or near the lowest astronomical tide (LAT)

Question 12

MHWS
MHWN
MLWN
MLWS

Answer 12

Mean High Water Spring
Mean High Water Neap
Mean Low Water Neap
Mean Low Water Spring

Question 13

Neap tide

This happens at what stage of the moon cycle

Answer 13

Smaller tidal range
Lower highs and higher lows

Happens in the first and last quarter of the moon’s cycle

Question 14

Spring tide

What time of the moon’s cycle does this occur

Answer 14

Greater tidal range
Higher highs and lower lows

Happens at the full and new moon

Question 15

Perigee

Perihelion

Answer 15

Moon closer to the earth

Sun is closer to the earth

Question 16

Apogee

Aphelion

Answer 16

Moon is further away from earth

Sun is further away from earth

Question 17

Diurnal

Answer 17

One high water and one low water in a cycle

Question 18

Semi-diurnal

Answer 18

2 high waters and 2 low waters in one cycle

Question 19

Semi-diurnal with diurnal inequalities

Answer 19

2 high waters and 2 low waters however they have uneven heights and times in one cycle

Question 20

5 factors affecting tides

Answer 20

Astronomical
Meteorological
Geographic
Resonance
Seismic waves

Question 21

4 major influences on tides

Answer 21

Declination and position of moon
Declination and position of sun
Latitude of the port
Natural resonance of the water

Question 22

Publication to look up time zones

Answer 22

Admiralty list of lights and radio signals