input to the local hydrologic system are rainfall, upland drainage, and tidal 

 inundations. Of these, rainfall is most often the source. However, low 

 levees or ridges in adjacent coastal areas may receive significant water inputs 

 through infrequent tidal or storm surges. Natural or artificial levees adjoining 

 major streams may receive major hydrologic inputs from periodic flooding. In 

 either situation, however, increasing elevation above the surrounding landscape 

 will reduce the frequency of inundation and thus the contribution from these 

 sources ( Penfound and Hathaway, 1938; O'Neil, 1949). 



Water is stored in the abiotic system as either surface water or ground- 

 water. Surface-water storage may exist temporarily as nonpoint surface runoff 

 or in small ponds or wet depressions in low areas on more extensive spoil banks. 

 Groundwater is the primary reservoir for water storage. 



The surface and groundwater storages interface through soil water storages. 

 The two soil water storages (macropore and micropore) are functions of soil 

 structure and soil texture, as covered previously in the uplands system discus- 

 sion. 



Soil water salinity is influenced by salt spray, tidal inundation, and, 

 in the case of dredged levees and spoil banks, the salinity of the parent mate- 

 rial. Salinity plays an important role in regulating the tolerance of levee 

 dgetation to soil moisture (Penfound and Hathaway, 1938; Penfound, 1952). 

 With progressive elevation of the soil surface above the water level, there is 

 a progressive decrease in soil water salinity; tidal inundation is decreased 

 and surface water percolation is increased (Penfound and Hathaway, 1938). Soil 

 texture and soil structure regulate the rate of percolation. 



Evaporation occurs through pathways similar to those of the upland model. 

 Moisture losses result from micropore water, from plant transpiration, and from 

 the surface of existing standing water. Climatic conditions regulate the evapo- 

 ration rate from these sources. Soil heat, soil structure, amount of organic 

 detritus in the soil, and plant cover regulate the rate of micropore water evapo- 

 ration. 



Surface water percolation into the soil macropore spaces is regulated by 

 land slope and vegetative cover. Increasing land slope tends to reduce perco- 

 lation rates, but the presence of plant cover will increase this rate (Spurr, 

 1964). Water filtering through the soil horizons may enter the groundwater 

 storage or be retained as soil mosture. The rate and extent of downward 

 percolation is affected by soil structure, texture, clay content, and the 

 concentration of organic materials. Organic materials and clay particles have 

 high water-retention properties. In the case of man-made levees and spoil 

 banks, excavation leaves the parent material less compact than the original 

 state, increasing its permeability and susceptiblity to erosion (Fisher et al., 

 1973). Excavation in saline environments also facilitates the rapid oxidation 

 of organic soil materials, which leads to changes in soil pH and potential 

 shifts of plant composition. Throughout much of the low-lying coastal areas, 

 the groundwater level is near the surface and receives percolated water. The 



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