energy and expenditures by the private sector. The 

 Federal Water Pollution Control Amendments Act of 

 1972 and the Rivers and Harbors Act of 1899 are ex- 

 amples of this kind of control mechanism. 



The actions of government can significantly affect 

 the economy and the coastal ecosystem. For instance, 

 1976 Federal per capita outlays were $874 in Ver- 

 milion Parish, $1,192 in Cameron Parish, and $1,230 

 in Calcasieu Parish. In Calcasieu Parish alone this re- 

 sulted in a total Federal outlay of $164 million (U.S. 

 Department of Commerce 1976b). In the coastal par- 

 ishes (counties) 40 to 60% of the Federal funding is 

 administered by the Department of Health, Educa- 

 tion, and Welfare (HEW) and is distributed widely 

 among tlie population. In some parishes, however, 

 over 20% is administered by the Department of De- 

 fense through the U.S. Army Corps of Engineers. The 

 latter outlays are often for large construction projects 

 such as ship channels, storm levees, and river control 

 structures, and have resulted in the most significant 

 environmental modifications in the Chenier Plain (part 

 3.3). 



3.2.9 SUMMARY 



Mineral extraction is the major industry of the 

 Chenier Plain. The dollar value of minerals extracted 

 in 1974 was six times greater than the estimated total 

 value of the renewable resources. Of the latter, agri- 

 culture is valued at about $28 million, recreational 

 fishing and hunting at $21 million, and commercial 

 fishing at $12 million. 



About 1.4 X 10'^ kcal/km^ (3.6 x lO'^ kcal/ 

 mi^) or (1.4 x lO'^ Btu/mi^) of the sun's energy is 

 received in the Chenier Plain each year. Much of this 

 energy is used to heat the earth and to drive the hy- 

 drologic cycle and ultimately, on a worldwide scale, 

 to determine the climate and the ocean's circulation. 

 About 5.4xl0^kcal/kmVyear(1.4x 10'°kcal/miO 

 (5.6 X 10'° Btu/mi^) (or less than one-half of one 

 percent of the energy that strikes the Chenier Plain) is 

 fixed in chemical form (net photosynthesis). This is 

 the major renewable energy source on this planet, and 

 the only practical source of food. In comparison, the 

 fossil fuels extracted annually on the Chenier Plain 

 have an energy equivalent of about 1.7 x lO' kcal/ 

 km^ (4.4 X 10'°kcal/mi2)or(1.75x lO'^ Btu/mi^), 

 about three times that of photosynthesis or about 

 one percent of the sun's annual energy flux. Although 

 natural processes (including the formation of fossil 

 fuels) depend on the energy of the sun, our economy 

 depends heavUy on fossil fuels that armually in the 

 Chenier Plain actually represent much more energy 

 than is utilized in photosynthesis. Unfortunately, fos- 

 sil fuels are limited and are extracted at considerable 

 cost to the natural environment. Therefore, mineral 

 fuel extraction represents a trade-off between a photo- 

 synthesis-based long-term economy and a short-term 

 economy based on a concentrated, non-ienewable 

 energy source. In the following parts of this report, 

 the environmental costs of this trade-off are evaluated 

 both in terms of the direct environmental costs of 

 mineral fuel extraction and of the costs that arise in- 

 directly from tlie use of mineral fuels to drive our 

 economy. 



3.3 HYDRODYNAMICS 



3.3.1 INTRODUCTION 



Water is an essential factor for the estabUshment 

 and maintenance of coastal ecosystems. Water is ne- 

 cessary for the existence of nearshore and estuarine 

 species, for sediment deposition, and for transporting 

 minerals and detritus. Water flow and quality maintain 

 the transition zone between land and sea. 



The single most important driving force respon- 

 sible for water level fluctuations, salinity changes, and 

 circulation is the sun. The sun controls seasonal warm- 

 ing and cooling of the earth, seasonal storage and re- 

 lease of precipitation (river discharge patterns), wind 

 patterns, weather systems, seasonal concentration and 

 dilution of salts, and circulation. The combined effects 

 of sun and moon also control the tides. Indirectly, 

 the sun is responsible for storms— from small local 

 summer thundershowers to massive hurricanes that 

 cause dramatic, though ephemeral, variations in water 

 level, saUnity, and circulation. 



Geomorphic processes also affect water level, sa- 

 Unity, and circulation. Sea level rise and land subsid- 

 ence lower the level of land relative to the sea, increas- 

 ing the amount of land inundation. Basin topography 

 strongly affects circulation and sahnity. For example, 

 a deep tidal pass carries larger volumes of water into 

 an estuary than does a shallow pass, and this in turn 

 affects salinity. 



Man also changes coastal systems. Hydrologic 

 changes are associated with the construction of canals, 

 impoundments, and dams, but these changes are in- 

 frequently studied; consequently total impacts are 

 difficult to assess. These cumulative impacts shift na- 

 tural cycles of freshwater supply, modify circulation, 

 and allow saltwater intrusion. 



This section identifies and discusses major hydro- 

 dynamic processes in Chenier Plain basins. Modifica- 

 tion of these processes by man and the resulting ef- 

 fects are also documented. 



3.3.2 APPROACH 



Historical studies of estuarine circulation have 

 been conducted in drowned river valley estuaries, e.g., 

 Chesapeake Bay. Most of the information collected 

 for these estuaries does not apply to shallow bar-built 

 estuaries hke those found along the Chenier Plain. 

 Hydrography and hydrology predicted by models of 

 river valley estuaries do not fit conditions found in 

 areas with broad expanses of marshes cut by tidal 

 channels. 



The processes that control circulation in shallow 

 estuaries are river discharge, tides, winds, evaporation, 

 and precipitation. These processes do not operate 

 equally over a basin. Lee and Rooth (1972) have sug- 

 gested a modular approach to the description of shal- 

 low estuaries. They offer a quahtative estimate of im- 

 portant processes by dividing the basin into subunits 

 or blocks, each dominated by a single process. Initially 



61 



