Table h - Tidal Ranges --Gu lf of Mexi co 



Coastal Area 



Reference Station 



Approximate 



Tidal Ranges (ft. ) 



Key West» St. Marks 

 R. 5 Tampa Bay 



Pensacolaj Mobile^ 

 Galveston 



Tarpon Belly St. George «-2-i4. 



Keys, Fla, Sound, Fla. 



St. George Port Isabel, 



Soundj Fla. Texas -^;i-l-2 



^Spring range 

 -)h;- Diurnal Range 



Table 5 - Tidal Ranges - Pacific Coast 



Coastal Area 



Reference Station 



From 



To 



Approximate 



Tidal Ranges (ft .) 



San Diego, Los Angeles 



San Francisco 

 San Francisco, Hiirabolt 



Bay 

 Humboldt Bay, Astoria 

 Aberdeen, Wash, 

 Seattle., Wash, 



Point Loma, Cape Mendocino 



Calif. ' Calif. 5-6 



Cape Mendocino Siuslaw River, 



Oregon 6-7 



Siuslaw River Columbia River 7-8 



Col-ojnbia River Fort Townsend^Wash. 8-9 



Puget Sound, Wash. 



10-lii 



57. Wind Set"Up . - In most coastal locations, severe storms cause 

 an increase in water level above that due to tidal action, if the wind 

 drives water ashore more rapidly than subsurface return flows can carry 

 it to sea. This effect is inpreased in gradually vshoaling, narrovjing, 

 open mouth bays. Set-up due to "wind occurring at the same tim.e as high 

 tides causes what are known as storai tides, which, especially in hurricane 

 regions, may be significantly higher than normal tidal action. For example, 

 Galveston^ Texas, where the normal tidal range is 1 to 2 feet^ ex- 

 perienced a hurricane in 1900 which caused storm water levels up to l5 

 feet J and in 1915 one which caused a storm, tide height of 12.5 feet. 



Water levels may also be reduced by wind action in the opposite direction. 



58, Seiches. - Every land-locked or semi-land -locked body of water 

 may be subject to regular short period oscillations which are a function 

 of the harmonic characteristics of the basin. Any change in water surface 

 elevation m.ay start these oscillations which are known as seiches. There 

 is one natural period for longitudinal oscillations and a second for 

 transverse oscillations. Depending on the dimensions of the body of water 

 and the mean depth along the axis of oscillations the period of the sieche 

 m.ay be either the natural period or some harmonic of the period. The 

 natural period^ or time of osciilstionj is independent of the am.plitude of 

 the, seiche. This time of oscillation may be calculated by the formula 



(lU) 



la 



