Ouachita River Floodplain Restoration Upper Ouachita NWR, Louisiana

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1 Ouachita River Floodplain Restoration Upper Ouachita NWR, Louisiana Interior Hydrologic Restoration Plan Mollicy Farms Unit The Nature Conservancy Louisiana Field Office 2011

2 Cover: Sediment laden water fills the Mollicy Farms Unit of the Upper Ouachita NWR shortly after the Ouachita River levee breached as a result of a historic high water event in May 2009 (USFWS).

3 Contents Background. 1 Monitoring... 3 Levee Removal... 4 Interior Restoration Restoration Map Extents (Current View). 7 Restoration Map Extents (Historic View) Shiloh Creek... 9 Deep Slough Bear Break Haase Wallow Mollicy Bayou Moist Soil/Rice Bayou de Butte

4 Background The Nature Conservancy (Conservancy) and the U.S. Fish and Wildlife Service (USFWS) have partnered to implement a phased floodplain restoration project on the Mollicy Farms Unit of the Upper Ouachita National Wildlife Refuge in northeastern Louisiana. Expected outcomes include a reduction in nutrients and sediments exported to the Ouachita River and increased productivity resulting from reestablishment of floodplain functions and processes. Southern forested floodplains provide critical ecosystem services including: 1) sediment and contaminant filtration, 2) excess nutrient assimilation, 3) atmospheric carbon dioxide sequestration, 4) flood control, and 5) valuable renewable natural resource production. Unfortunately, many of our floodplain forests have been converted to other uses and cut off from the natural pattern of seasonal flood pulses leading to species loss, impaired water quality and reduced productivity. Insert project map Mollicy Farms Unit This 80,000 acre restoration project (20,000 acres bottomland together with approximately 60,000 acres upland watershed) is the largest floodplain restoration effort underway in the U.S. Lessons learned here will be invaluable for shaping future restoration activities of even greater scale within the Mississippi Valley and elsewhere. 1

5 Mollicy Farms was cleared for row crop agriculture in In the ensuing years, 17 miles of levee, averaging 30 feet tall and 150 wide at base, were constructed surrounding 16,000 acres to reduce flooding. Subsequent modifications to interior drainages continued to reduce natural sloughs and bayous to a series of mostly straight line ditches. The construction of the main levee and disruption of natural flooding cycles has functionally disconnected the floodplain from the Ouachita River For decades the tract was a closed system, only interacting with the river via a pump that brought water on and off of the site for rice production. Acquisition of the tract by USFWS for inclusion within the Upper Ouachita National Wildlife Refuge began in the early 1990 s with the last parcel having been acquired in From 1998 through 2001, USFWS reforested over 11,000 acres with bottomland hardwood species making Mollicy Farms the site of one of the Nation s largest bottomland afforestation projects

6 Monitoring Under the leadership of the Conservancy, a multi-year monitoring program has been implemented that will document trends in water quality, ecosystem services and the response of the biological community to reestablishment of the flood pulse and restoration of internal waterways. Sampling occurs both within the heavily disturbed Mollicy Farms Unit as well as the relatively intact and forested western floodplain of the Ouachita River. Flood pulse monitoring occurs at water quality monitoring stations located along drainages consisting of a carousel type ISCO sampler paired with a second YSI sampling unit that transmits and makes data available for viewing in real time. Aquatic invertebrates, herpetofauna and fishes are important measures of the biological integrity of aquatic habitats and are sampled across the project area throughout the year in order to capture a variety of hydrologic conditions. The data collected over the next several years will allow for an assessment of the effectiveness of the restoration work and inform the partnership when planning for additional levee breaches and restoration of the interior hydrology of Mollicy Farms. 3

7 Levee Removal Historic high water conditions during May 2009 resulted in two uncontrolled levee breaches. In the summer of 2010 under the leadership of USFWS, over 3.25 million cubic yards of dirt were removed leaving four additional breaches in the main Ouachita River levee and restoring flow to waterways and drainages that have been functionally disconnected from the river for decades. Breaches were strategically located and designed to restore functionality to the floodplain while minimizing scour, riverbank degradation, headcut development or adverse impacts to the Ouachita River channel and water quality. Locations of uncontrolled levee breaches (2009) 4

8 Interior Restoration Historically there were three primary drainages that facilitated the watering and dewatering of the site. They are Shiloh Creek, Mollicy Bayou and Bayou de Butte. However, as evidenced by this aerial imagery taken after the site was deforested but prior to any hydrologic modification, these drainages contained numerous lesser drainages and communicated through a complex network of cypress brakes, sloughs, and ephemeral creeks and bayous depending on water levels. Results from the first year of water quality monitoring after the breaches were in place suggests that the tail end of the flood pulse may be a time of significant release of sediments and potential contaminants into the Ouachita River. Restoration of former watersheds and streams interior to the tract and reconnection of these streams to their headwaters can be expected to reduce sedimentation and improve water quality in the future. 5

9 Due to the pervasive alteration of waterways and drainages, interior hydrology will never be restored to historic conditions. Rather, the goal is to undertake a series of corrective actions that will begin to restore functionality to the floodplain. Proposed actions are presented in a series of seven Restoration Maps covering the Mollicy Farms footprint. For comparison purposes, the extents of these maps are displayed in the following pages on both present day and historic imagery prior to hydrologic alteration. Each Restoration Map displays the activities needed to improve flow within the drainage and associated wetlands and headwaters. Activities are primarily associated with either facilitating or impeding flow as needed to promote a more controlled watering and dewatering of the site. Flow Facilitation Actions include construction of openings in roads, levees and berms, removal of culverts and water control gates, and construction of low-water road crossings. Flow Impediment Actions largely include placement of plugs within existing drainage ditches, borrow pits, and water courses in order to focus flow into restored stream channels. Creating a new stream channel (Benson Slash, AR 2006) A rebuilt functional channel (Benson Slash, AR 2007) 6

10 Restoration Map Extents

11 Restoration Map Extents

12 Shiloh Creek Shiloh Creek originates in the pine flatwoods northeast of Mollicy Farms and also drains the forested floodplain to the north during periods of peak flow on the Ouachita River. It historically entered from the north in at least two locations and moved southeast before entering the Ouachita River. Both the entrances and exit had been truncated by the main containment levee prior to the manufacturing of breaches in the summer of 2010 (Points A) and the uncontrolled breach that occurred during flooding in May 2009 (Point B). When the Ouachita River was below bankfull prior to 2010, Shiloh moved east to west via a canal constructed along the outside of the northern levee. Surface flow within the Mollicy footprint moved through a series of borrow pits and canals along the interior edge of the northern and western levee, south to the pump that was located in Section 17, T22N R4E to be removed to the Ouachita River. At the locations of the three manufactured levee breaches, the interior and exterior drainage ditches need to be well plugged on either side of the newly restored channels (exemplified by Point C) to ensure that water flows through the breaches and not overland back into the ditches. A reservoir had been created by impounding Shiloh at Point D. A modest breach was created here but needs to be expanded to handle the large amount of water moving through the channel in this locale. Further down the channel at the south end of Haggerty Lake, a low water vehicle crossing impedes flow during periods of low water (Point E). Should this location continue to provide a valuable crossing point for vehicles a bridge or considerably larger culvert needs to be installed. Point F is the location of a reestablished portion of the creek channel. Because this area had filled in over time due to lack of use, it was dug out to approximately 5 feet wide to encourage channel reestablishment once the levee was removed. Rapid movement of water was observed in this location as flooding subsided in June This reach should have a greater width to depth ratio and channel cross-sectional area than it appears to have at present. To ensure that incising does not occur it needs to be widened to approximate the width of the channel above and below or have the gradient otherwise stabilized. It is recommended that cross sections be established to monitor channel dimension and profile to inform future actions here. 9

13 Shiloh Creek Mollicy Bayou C B A A D F A E

14 Deep Slough Deep Slough has its origin in a large wetland break that historically occupied a river meander scar across portions of Sections 34 and 35, T23N R4E and Sections 2 and 3, T22N R4E. This break was responsible for recharging Deep Slough which drained west to the Ouachita River prior to construction of the main levee. After levee construction, the exit pathway for water from this drainage was accomplished through a series of borrow pits and canals running south along the interior of the western boundary levee to the Ouachita River via the pump. The most southern accidental breach that occurred during the 2009 flood created an outlet for water in the vicinity of its historic confluence with the Ouachita River. Subsequent modifications to road crossings and berms has rerouted the water through this new breach. This modified path for Deep Slough to the Ouachita River allows water to flow freely and is considered an acceptable situation for the foreseeable future. Drainage in the upper reaches of Deep Slough has been complicated by the construction of two roads, Kelby Road running north to sough and the North Gate Road running east to west. These raised roads have effectively cut off Deep Slough from the its source in the historic wetland break previously described. Point A indicates a location where the road is frequently impassable due to high water moving from east to west along its historic course. It is recommended that the road be abandoned here and the historic course be restored in this location. This would require removing the intersection including the opening of the two deep ditches that run on either side of the North Gate Road so that they may freely enter Deep Slough. The ditch north of Deep Slough should be plugged at either end (Point B) to discourage water being diverted from Deep Slough. During the May 2009 flood, the breach that resulted south of Deep Slough occurred with such force that sand filled in portions of Deep Slough (Point C). This area needs to be monitored to ensure that subsequent flow is removing this blockage. It may become necessary at a point in the future to manually remove the sand. It is important that the ditch running south along the interior of the western boundary levee be adequately plugged (Point D) north and south of the newly engineered confluence of Deep Slough and the Ouachita River. Point E marks the location of the most southern accidental breach that occurred during the 2009 flood. 11

15 Deep Slough C E B A D

16 Bear Break Bear Break occupies a large river meander scar within the northeast portion of Mollicy Farms. Historically it was charged from Hog Wallow Slough which drained the pine flatwoods to the east and entered the wetland complex north of Bear Break in Section 35, T23N R4E. Hog Wallow Slough was truncated by the main containment levee on the northeast border on Mollicy Farms. There are no plans at present to reconnect Hog Wallow Slough due to the considerable financial costs involved and the potential for disruption to refuge activities. Bear Break was historically a major source of water to Mollicy Bayou to the south. Present day Bear Brake occupies an essentially closed basin that is bounded on all sides by drainage ditches and associated berms, spoil piles, and low levees. Water in-flow and out-flow is accomplished by operation of water control structures in the border ditches and berms. Notwithstanding, rehabilitation of the historic wetlands to the north and reestablishment of the north to south flow of the drainage can be accomplished with a minimum of actions and will restore flow to a historically significant drainage. Recharge from the wetlands to the north is currently prohibited by the presence of the North Gate Road running east to west. This road together with the two deep ditches along it on the north and south divert water moving south from the northeast corner of Mollicy Farms to the west. The road bisects the historic wetland break in this area and should be abandoned and reengineered to facilitate flow to the south. Point A indicates an area where the road should be cut to facilitate north to south flow. This was the historic confluence of Hog Wallow Slough and the wetland break. Considerable overland flow still occurs in this area and should be routed through this breach by plugging the ditches on either side of the North Gate Road. A similar action is needed at Point B where Bear Break is prohibited from joining Mollicy Bayou by an east west ditch. This ditch should be breached with plugs on either side. At Point C, ditches on either side of a raised pipeline should be plugged to encourage north to south movement of water. Further north to south flow can be achieved by removing a low water berm along the south ditch on the North Gate Road. This berm currently encourages water to move toward the west. 13

17 Bear Break C D B A Rehabilitated Stream Course Action Required to Facilitate Flow Flow Impediment Action Required Wetland Miles

18 Haase Wallow Haase Wallow is a previously unnamed but important drainage that has its origin in the same large historic cypress break that recharged Deep Slough and Bear Break. It was also fed by Pistol Break, a cypress wetland occupying Section 4, T22N R4E. Historically Haase Wallow drained to the south entering Mollicy Bayou within Section 16, T22N R4E, also referred to as the School Board tract. Prior to 2010, this drainage was essentially a closed system. Water entered the ditch along the interior of the western boundary levee and moved to the Ouachita River via the pump located at the northwestern corner of the School Board tract. During 2010, the pump was removed and the boundary levee breached in this location which restored connectivity to the Ouachita River. Drainage in the upper reaches of Haase Wallow has been complicated by the construction of the North Gate Road running east to west. This raised road and associated ditches running parallel on the north and south have effectively cut off the drainage from its source. Point A indicates an area where a large cut needs to be made in the road. Currently, no plugs are recommended in the ditches. This road severely complicates restoration of three important drainages on Mollicy Farms. Ultimately, numerous openings in this road need to be created and plugs installed in the ditches to encourage the western and southern drainage that occurred historically. At Point B a raised pipeline is directing water east and west. Where possible it should be lowered to encourage north to south movement of water. Point C indicates an area where the drainage crosses the Kelby Road. The road in this area should be cut and abandoned to facilitate flow. Ditches on either side of the cut should be plugged. Point D indicates a low water crossing of the Salt Water Road. The crossing should be removed here and the road abandoned to facilitate flow. A plug is needed at Point E to prohibit water that has been draining to the west. At Point F, obstructions to the drainages should be removed to encourage north to south flow. Point G indicates two areas along the Pump Station Road that are in need of a breach and associated plugs to facilitate the movement of water from Haase Wallow to its confluence with Mollicy Bayou. 15

19 E F D Haase Wallow G C B A

20 Mollicy Bayou The origins of Mollicy Bayou are both on the pine flatwoods to the east as well as interior to the site as it captured the drainages of Bear Break and Haase Wallow before entering the Ouachita River near the corner of the School Board tract. The basin drained by Mollicy Bayou has been truncated by a water diversion canal that diverted flow to the south along the interior levee ditch ultimately back up north to the pump at the northwest corner of the School Board tract. At peak flood stage a lesser amount of water from the pine flatwoods appears to bypass the diversion canal and flow across the interior of Mollicy Farms in the area of its former pathway through a complex patchwork of right angle ditches, roads and berms. Approximately two miles of the channel have been replaced with straight line ditches and will need to be reestablished. Point A indicates the approximate historic course of the waterway to be recreated. The ultimate route will need to be surveyed and engineered to ensure adequate flow while minimizing incising and may make use of both present day ditch fragments as well as newly engineered channel. Once the former channel of Mollicy Bayou has been reestablished, the diversion canal will need to be plugged (Point A). Point C indicates an area where a plug needs to be installed at the confluence of two ditches. A large cut needs to be made in the Kelby Road to facilitate flow to the west just below the confluence of Bear Break and Mollicy Bayou (Point D). The ditches on either side of this road will need to be plugged and the road abandoned. At Point E a small interior levee designed to separate the School Board tract from Mud Lake should be breached in this location so that water can move freely between the two. Point F is the historic location of the main channel. It has been severely compromised here as elevated roads truncated the channel in an effort to provide access to the pump formerly located here. The channel should be reestablished here to approximate the width of the reaches below and above. Point G marks the location of the manufactured levee breach created in

21 Mollicy Bayou G F B E D C A

22 Moist Soil/Rice C In a given year the refuge maintains 850 acres of rice and 850 acres of moist soil management within the area delineated. Historically, the movement of water to and from the fields via the pump in Section 17, T22N R4E occupied a sizeable footprint on Mollicy Farms and prohibited the restoration of streams and drainages. A B The goal for reengineering this area is to develop a new source of water and reduce the area involved in water transport and holding. Point A indicates a location at the western terminus of Three Mile Ditch where a new main levee breach or pipe should establish contact with the Ouachita River. Water can be moved east along the ditch to the fields and returned to the river at the same location. Point B indicates a second suitable location for returning water to the river. Restoration of degraded waterways can improve water quality before it reenters the Ouachita River. Pumping rice water off of the fields onto recently reforested areas (Point C) affords sediments and potential contaminants the opportunity to settle out of the water column as water moves overland. Minor drainages can be rehabilitated to facilitate flow in the desired direction. 19

23 Bayou de Butte B A Bayou de Butte originates in the pine flatwoods east of Mollicy Farms and moves southwest before turning west to the Ouachita River south of the southern containment levee. Construction of the levee in that location resulted in truncating Hog Slough and Little Hog Slough, so that they no longer flow into Bayou de Butte. During very large and prolonged Ouachita River flood events water in the pine flatwoods flows from north to south along the east portion of the Mollicy Farms boundary levee. Such flood waters contribute to higher than normal flows in Bayou de Butte and may be a contributing factor to the washout of culverts along the South Gate Road as well as channel incision and instability observable within Bayou de Butte to the north of this road crossing. To alleviate this situation obstacles should be removed that would encourage some movement of water west across the Southern Reservoir. Point A indicates an area where several low berms prohibit water from moving west and should be removed. Point B indicates an area where road crossings need to be breached or culverts need to be installed. 20

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