HIGH WATER LINE 



high water line — The intersection of the plane 

 of high water with the shore; it varies daily 

 with changing lunar phases and meteorological 

 conditions. 



high water lunitidal interval — See lunitidal 

 interval. 



high water mark — An established reference mark 

 on a structure or natural object which indicates 

 the maximum observed stage of tide. (73) 



high water neaps — See mean high water neaps. 



high water of ordinary spring tides — (abbrevi- 

 ated HWOST). A tidal datum appearing in 

 some British publications, based on high water 

 of ordinary spring tides. (61 ) 



high water quadrature — See mean high water 

 neaps. 



high-water rock platform — A coastal terrace a 

 little below high tide level and coinciding with 

 the ground-water table resulting from wave ero- 

 sion of rocks which are relatively softer or more 

 decomposed above the ground- water table than 

 below. 



high water springs — See mean high water 

 springs. 



high water stand — The condition at high tide 

 when there is no change in the height of the 

 water level. A similar condition at low tide is 

 called low water stand. (68) 



hindcasting — The determining of a predictand or 

 predictands for some past situation using a 

 known predictor or predictors. For example, a 

 wave hindcast would be based upon wind direc- 

 tion, speed, duration, and perhaps fetch for 

 some past situation. These data could be 

 utilized in wave forecasting techniques to esti- 

 mate the wave direction, height, and period. 



hinge crack — (or loeight crack). A crack in sea 

 ice running parallel and adjacent to a pressure 

 ridge. Hinge cracks are believed to be caused 

 by the weight of the pressure ridge. (59) 



hinter deep — A deep sea trough on the convex 

 side of an island arc. (2) See deep, trench. 



hinter surf beds — Littoral, lagoonal, deltaic, and 

 tidal flat deposits which form the continental 

 shelf. (2) 



histogram — A graphical representation of a fre- 

 quency distribution. The range of the variable 

 is divided into class intervals for which the 

 frequency of occurrence is represented by a rec- 

 tangular column; the height of the column is 

 proportional to the frequency of observations 

 within the interval. (5) 



historical chart — (or First Approximation 

 chart) . A chart based on data from previous 

 years to determine probable oceanographic pat- 

 terns for a spcified time. 



hodograph — In general (mathematics), the locus 

 of one end of a variable vector as the other end 

 remains fixed. A common hodograph in ocean- 

 ography represents a tidal current or a compo- 

 nent of a tidal current for a complete tide cycle. 

 The current speed is shown by the length of the 



arrow ; the change in time is shown by the differ- 

 ent directions of the arrow from a common 

 center. See Ekman Spiral, current ellipse. 



hogback coast — See wave-straightened coast. 



holdfast — A basal attachment structure of algae, 

 ranging in complexity from the simple or modi- 

 fied cells of filamentous algae to the massive root- 

 like structures of the kelp. 



holding ground — The sea bottom of an anchor- 

 age designated as good or poor, depending upon 

 whether an anchor holds, catches, or drags. 

 Mud or silt usually is good holding ground. 

 Rock, gravel, or hard packed sand often is poor 

 holding ground, since an anchor often will drag, 

 snag, or become fouled. 



hole — 1. An abrupt hollow in the ground or ocean 

 floor. 



2. An opening through a piece of sea ice, or 

 an open space between ice cakes. Such an 

 opening made to permit observation of the height 

 of the tide is called a tide hole. 



3. A small bay, particularly in New England. 

 (68) 



holophytic nutrition — (or photoautotrophic 

 nutrition, phototrophic nutrition). That proc- 

 ess by which an organism manufactures its food 

 by using the energy of the sun. See auto- 

 trophic nutrition. 



holoplankton — (or permanent plankton). Or- 

 ganisms living their complete life cycle in the 

 floating state. 



holosteric barometer — Rare. See aneroid ba- 

 rometer. 



holothurian — See sea cucumber. 



holozoic nutrition — That process by which an 

 organism ingests solid food and digests it inter- 

 nally ; typical of free living animals. 

 See heterotrophic nutrition. 



homogeneous fluid — A fluid within which the 

 density is uniform. (5) 



homopycnal (equally dense) inflow — A sediment- 

 laden stream enters a basin filled with a water 

 of comparable density, as when a stream enters 

 a fresh-water lake. The resulting delta is the 

 classical type with top-, fore-, and bottom-set 

 beds. (2) 



homothermal — See isothermal. 



honeycombing — During the final disintegration 

 of floating ice, the process of partial melting that 

 leaves the piece of ice filled with pockets of 

 water. Honeycombed ice is generally soft and 

 spongy, and floats low in the water. Usually 

 only small pieces of ice are found in a honey- 

 combed state (such as growlers or brash ice), 

 although occasionally in a calm sea icebergs or 

 big ice floes may become honeycombed without 

 breaking up. 



hook — 1. A spit or narrow cape of sand or gravel 

 whose outer end bends sharply landward. (68) 

 2. See recurved spit. 



hooked bay — An open bay or bight having only 

 one headland. (2) 



78 



