of factors including salinity, bottom topography, equipment availability, transport 

 distances, and project schedules. 



Weirs, retaining structures, and dikes to protect the site should be designed to best 

 suit the wetland to be built. This could range from no structure in a very low energy 

 area, to a temporary sand dike enclosing the wetland until it becomes established, to a 

 permanent riprap dike around an area of very high energy. 



If dredged or fill material is used at the site, care should be taken to place the 

 material at desired elevations or to shape it after it is in place. If hydraulically pumped 

 material is used, consolidation rates must be calculated accurately or the completed 

 site could be either above or below the desired wetlands elevation. Much of this work 

 can be accomplished by moving the disposal pipe at intervals and/ or by using heavy 

 equipment to shape the site. Special dredging technology exists that can be used for 

 placement of dredged material to a specified elevation. 22,23 



PLANT PROPAGATION 



The biological aspects of wetland development include selection of propagules, 

 preparation of soil to receive propagules, actual plant establishment, and monitoring 

 to determine plant survival." Sketches of typical plant associations based on 

 elevation and water level in wetlands of various regions of the United States are 

 shown in Figures 1-4. 



Soil Bed Preparation 



Soil tests for texture, salinity, nutrients, heavy metals and other contaminants, and 

 pH should reveal any need for changes in the soil chemistry. Fertilization is 

 frequently recommended. Grading may be necessary to ensure proper elevations. In 

 sandy or well-drained soils, grading usually presents no problem; however, grading 

 by conventional means is usually impossible on silt and clay soils. In the latter 

 situation elevation changes may be made through use of high-pressure hoses or pipes. 

 In any case, a well-prepared bed to receive propagules will help ensure site success. 



Species and Propagule Selection 



Salinity, tidal range, current and flood stages, soil texture, wind and wave action, 

 contaminant tolerance, outside influences such as human disturbance and animal 

 grazing, and costs are all factors that must be considered carefully when site 

 vegetation is selected. Plant species should be selected to suit the project goal. They 

 should be from a nearby location, adapted to local conditions, and readily available 

 at a reasonable cost. They should be tolerant of site soil, climate, water, and 

 contaminant conditions; have desirable growth characteristics; and have low 

 maintenance requirements. The propagule type should be selected on the basis of 

 availability; collecting, handling, storing, and planting ease; project goals; freedom 

 from disease; need for immediate plant cover; and site elevation. Careful considera- 

 tion should be given to cost. For example, sprigs are much more expensive than seeds 

 for most species; however, sprigs are usually much more successful than seeds. There 

 are situations, however, in which seeds are equally as effective as sprigs. 



Planting Design 



In general, it is desirable to encourage plant species diversity because many 

 wetlands are naturally diverse; diversity will aid if one species dies but others survive. 

 Diversity of habitats will encourage diversity of wildlife. 



Spacing of plant propagules is very site specific and depends upon factors such as 

 the soil texture, type of propagule, length of growing season, energy regime, and 

 desired rate of plant cover. Planting with about a 1-m spacing is generally a good 

 compromise between high costs and adequate cover, but spacing of 0.3 to 1.5 meters 

 may be successfully used in many instances. Costs increase dramatically with closer 

 spacing. If a site is very unstable or is subject to heavy wildlife pressures or physical 



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