intermediate marsh system occurs near the Intracoastal Waterway. Apparently, the freshwater 

 introduction system presently there is maintaining low level salinities. Plant species observed in the 

 fresh to intermediate marsh in fall 1987 were black willow (Salix nigra), pondweed (Potomogeton 

 sp.), bulltongue (Sagittaria lancifolia), alligatorweed (Altemanthera philoxeroides), Jamaica sawgrass 

 {Cladium jamaicense), water primrose (Ludwigia repens), seashore paspalum (Paspalum vaginatum), 

 and wiregrass. 



Watershed objectives are to provide storm flood control and to increase marsh productivity by 

 managing saltwater flow into the system. Initial management plans include a 2-year program of 

 drawdowns and semi-static water control. Management thereafter will be adjusted as needed to 

 apply the concept of holistic management. Data that may be used to accomplish this goal are plant 

 salinity tolerances (SCS 1977), marsh open water salinities (Sabine National Wildlife Refuge, 

 unpubl. data 1988), digitized habitat imagery (Liebowitz and Hill 1988), streamside sedimentation 

 rates (Cahoon et al. 1988), estuarine organism ingress and egress data (Herke et al. 1987), channel 

 water levels, soil redox potential, and evapotranspiration losses. Although nature will maintain 

 the controls, management flexibility is essential. Natural parameters influencing management 

 decisions are sea level rise, nearness to saltwater sources, lack of freshwater sources, physical water 

 action (lunar and wind tides, channel width and depth, and increasing fetch), tropical storms, 

 drought, and plant adaptations to such an environment. 



WEIR MANAGEMENT 



Five weirs are presently under construction. Noname and Peconi Bayou weirs will have fixed- 

 crest weirs with four openings 2.3 m wide and crests set 0.2 m below mean marsh level (MML). 

 Mangrove and Lambert Bayou will have variable crest weirs with four openings 3.1 m wide and 

 capable of a crest of 1.2 m below MML. The Grand Bayou variable crest weir will have five 

 openings 3.1 m wide, and four openings having flapgates leading out and low level capabilities of 

 1.2 m below MML. Except for the Grand Bayou weir, all other weirs will be equipped with three 

 15-cm by 1.2-m vertical slots. The middle structure at Grand Bayou will be a boat bay for 

 estuarine organism ingress and sport fishermen access. Channels leading to each weir will be 

 riprapped at a 45° angle to assist estuarine organism ingress and egress. 



During the first years of water management (phase 1) there will be drawdown from 15 February 

 to 15 July. The drawdown is designed to lower water levels to 15 cm below mean marsh elevation 

 at the 5 ppt isohaline line. Flapgates at Grand Bayou will facilitate the drawdown, while impeding 

 inward tidal flow. At least one vertical slot at each weir will remain open. 



During the drawdown period, Sabine National Wildlife Refuge (NWR) will manage the weirs to 

 allow for seasonal estuarine organism ingress and egress, to negate salt burns caused by extended 

 drought, and to release flood waters caused by tropical storms and unusually heavy precipitation. 

 After the drawdown, variable crest weirs will be set at 21 cm below MML, and the boat bay will 

 be opened. Miami Land Corporation will supply one person to assist with weir openings and 

 closings. 



Third year (phase 2) water management will be considered semi-static, and emphasis placed on 

 enhancing fish and wildlife diversity. All weir crests will be set at 21 cm below MML; all vertical 

 sl6ts, the boat bay, and one gate at Grand Bayou will remain open. During peak post-larva ingress 

 and juvenile organism egress (brown shrimp, Penaeus aztecus, and white shrimp, P. setiferus), one 

 more gate will be opened at Grand Bayou. 



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