December 17, 2015

Guest Column:
A proposal for ending the drainage mess in the Cape Point area


By CHRIS EGGHART


The torrential week-long rains of late September and early October, coupled with overwash generated by an offshore tropical system, resulted in unprecedented levels of flooding in the Cape Point area. Portions of Lighthouse Road, Cape Point Campground, and Ramp 43 and Ramp 44 were closed for weeks. Standing water covered the road surface and inundated the campground for several months.

Beyond the dune line, the Dredge Pond basin, also known as the "Salt Pond," filled to cover the interior of Cape Point. Hatteras Island residents and visitors alike are becoming all too familiar with flooding in this area. Once a rare and short-lived occurrence, flooding of this area seems to be becoming more common and acute. The inundation of 2015 may have been the worst to date.

Climate change and sea level rise may well be contributing to the frequency and severity of flooding along the interior of the Cape Point and elsewhere on the island. These twin forces will surely challenge our island in the coming decades and beyond. However, the immediate problem at Cape Point is entirely local in origin.

HOW WE GOT HERE

The root cause of the flooding lies in the construction of the protective dune system by the Civilian Conservation Corps (CCC) during the 1930s. Erection of the dune line severed the natural hydrological connection between the interior of Cape Point and the ocean. The result is a large artificial basin that collects stormwater that has nowhere else to go.

To mitigate this, the National Park Service connected a ditched stream that circumvents the campground to a steel culvert that runs under the dune line just west of Ramp 45. Presumably, this work was undertaken in association with the development of the campground and other park facilities. The enhanced steam channel connects with the roadside ditches near the campground entrance.

Two control structures were installed and maintained to regulate water passing through the channelized system. One is located on a dirt track that crosses the stream just west of the campground and the second near the entrance to the steel culvert extends under the dune line. A third opportunity to evacuate excess water was purportedly located along the north beach approximately half way between the Ramp 43 and the current lighthouse location. Here a straight line ditch runs from Lighthouse Road northeast to terminate along the dune line.

The recurring flooding of the last decade or so is the direct result of stormwater purposefully being blocked from entering the steel culvert west of Ramp 45. This blockage appears to have been started around 2004 in response to a Notice of Violation (NOV) issued to the Park Service by what was then known as the North Carolina Division of Water Quality. The NOV, dated Sept 16, 2004, specifically cites concern that the above described drainage system may be lowering water levels in the wetlands that characterize areas along Lighthouse Road.

The NOV was recently located by NPS staff and widely distributed by the seashore's new Superintendent David Hallac, who arrived last January and witnessed his first flooding event in the Cape Point area in early October.

When I read a copy of the NOV, it was clear to me that the State of North Carolina never intended for the hydrological connection to the ocean to be fully severed. Rather, the NOV specifically directed the NPS to produce “a restoration plan [which] should include a draft management plan that addresses maintaining the appropriate water levels in the wetland by modifying the drainage culvert.”

The NOV further directed that “the plan should include a water level monitoring plan utilizing the existing staff gauge located at the upstream opening of the culvert.”

The NPS officially responded in a letter dated October 25, 2004. This letter, signed by then superintendent Lawrence Belli, was also located and widely distributed by the current superintendent Hallac.

The response letter addresses concerns raised in the NOV and presents an action plan to bring the park into compliance. Called for in the action plan was the immediate construction of two modified water control structures that would more effectively regulate water flow. This was to be followed by the development of a Wetlands Management Plan. It would appear that neither of these actions was ever carried out.

None of the proposed modified water control structures are known to have been built, nor does any Wetlands Management Plan appear to have been developed. Rather than complying with terms of the NOV issued by the State of North Carolina, the NPS appears to have simply closed the sluice gate that allows water to enter the culvert and flow under the dune or otherwise blocked the drainage. This action has directly resulted in ever worsening stormwater accumulations within the interior portions of the Cape Point area.

In mid-December, Ramp 44 was still closed by standing water.

What is perhaps the most unfortunate aspect of this situation, over and beyond the loss of recreational opportunities provided by the campground and the beach access points, is the environmental and ecological detriment wrought by the standing water. The human-induced stormwater pooling behind the dunes has likely significantly degraded the quality and function of the wetlands in question.

What is ironic is that it remains unclear to what extent, or even if wetlands were ever being compromised in terms of water level draw down. It is possible and perhaps likely that the water conveyance and control infrastructure originally constructed by the NPS fairly closely mimicked the area’s natural hydrology, specifically its connection to the ocean that would be sustaining itself had the dune system not been constructed.

In short, the wetlands that the state of North Carolina sought to protect have been significantly degraded by severing their natural hydrological connectivity. This is expressed in the diminishment of critical wetland service functions to include: water quality, plant diversity, wildlife habitat, and aesthetic and cultural value.

Prior to drainage being blocked, this area along Lighthouse Road was --- at the very least -- a mix of quality, high functioning forested wetlands and scrub shrub wetlands. Not only is the aesthetic and cultural value of the natural resource being compromised, the dramatic die back in mature trees, scrub and other vegetation is clearly a major loss of wildlife habitat, and a detriment to plant diversity.

Plant diversity is also being compromised by the ongoing rapid spread of cattails which thrive where static water levels dominate. A larger threat to the diversity of the existing wetland plant communities is the invasive phragmites reed, which is making its presence known. Impact on the water quality function of wetlands is perhaps most troubling, particularly by way of soil filtration and nutrient uptake. What was once an optimal mix of small, fluctuating open water bodies and large areas of perennially and seasonally saturated soils is fast transitioning to a stagnant, cattail and reed-choked stormwater lagoon.

A PROPOSED WAY FORWARD

What is clearly needed is a way forward to rectify this unfortunate situation. A useful approach would be to split two separate but closely related needs.

These are how to:

1) Responsibly evacuate ocean overwash and extreme precipitation trapped behind the dune line as a result of hurricanes and other severe events.

2) Properly manage the normal water levels in the wetlands by controlling outflow through the trans-dune line culvert, as directed by the North Carolina regulatory authorities in their 2004 NOV issuance.

An apparent popular misconception is that the NPS is not able to evacuate water from behind the dune as it is polluted and/or contaminated by septic run-off. This is not substantiated. The misconception is apparently based on some limited recreational swimming and shellfish harvesting water quality monitoring efforts carried out by the Marine Fisheries Division of the North Carolina Department of Environmental Quality (DEQ).

This is the state agency under which the Division of Water Quality is now organized as the Water Resources Division. In the early 2000s, North Carolina DEQ identified elevated levels of enterococcus bacteria in beach water near the culvert outflow. The enterococcus bacterium is found in the intestinal tract of warm-blooded animals. It is harmless to humans but its presence is used in water monitoring as a marker for potentially harmful organisms.

The NPS sponsored more detailed water quality studies reported in "Assessment of Coastal Watershed Conditions at Cape Hatteras National Seashore, North Carolina," published May 2006. Mean fecal coli form levels in surface water swales in the Buxton area were analyzed in the study. For Buxton surface water, the concluded that “septic leachate contamination was minimal to non-existent and the periodic elevated fecal coliform bacteria counts were likely due to wild animals congregating at the swale sites” (NPS 2006:46).

Only a limited numbers of beach water samples containing enterococcus  were registered in the North Carolina DEQ monitoring study cited in the above NPS sponsored technical report. These were recorded during spring and summer of 2003 near where the culvert was discharging. The presence of potentially harmful bacterium was not established. Wildlife is a likely source of the enterococcus in the drainage water as well, not just in the interior swale wetlands but also from gulls, and other flocking shorebirds that gather around standing fresh and brackish water where it pools near the surf zone.  

The following proposal is made to mitigate the ongoing flooding issues at Cape Point as well as the resulting environmental damage and loss of recreational opportunities.

The NPS should immediately develop a water and wetlands management plan for the Cape Point area. This plan should be comprehensive in nature and address not only catastrophic stormwater evacuation and wetland protection along Lighthouse Road but also in the area of the Dredge Pond. Although this man-made feature lies outside the dune line, it nonetheless is integral to Cape Point’s hydrological regime and environmental condition.

To evacuate catastrophic storm water, it is proposed that a simple box weir be constructed at the head of the existing ditch east of Lighthouse Road where it meets the dune line. A box weir is typically a four-sided concrete structure open and grated on the top to let water flow in. Such a structure would connect to a concrete pipe that extends under the dune line and onto the North Beach. This pipe could be buried under the sand with the opening marked with deeply set posts. 

Following catastrophic events, the end of the pipe would simply be "daylighted" with a backhoe/loader and a drain channel initiated to the tide line. Once the excess water is evacuated, the pipe opening would be covered with treated wood and the sand pushed back by the loader to restore the beach contour. In this manner, the pipe would remain fully out of view and protected from storm tides. The great advantage of a box weir as a water control device is that it is self- regulating and only lowers water to a single pre-set level equal to the top of the structure.

Once catastrophic stormwaters are evacuated, appropriate water levels in the wetlands can be maintained by the two water control structures originally proposed by the NPS in response to the violation notice. This original proposal called for simple concrete structures that allowed treated wood slats to be inserted or removed for a determined flow level to the culvert near Ramp 45. This is in contrast to the existing drop gate installation.

Opening of the culvert near Ramp 45 would be accompanied by water quality monitoring. Should unacceptable bacteria counts be present, then a time-of-year restriction could be implemented that limits discharge to outside the recreational swimming season. However, any time-of-year restriction would likely not be warranted. Under normal summer conditions, sun induced evaporation and evapotranspiration by vegetation would likely remove sufficient water volumes to preclude any need for discharge under the dune. In years past, flooding has occurred almost entirely in the fall months as the sun angle recedes and the growing season wanes.

Finally, the management plan should address conditions around the Dredge Pond. The NPS should reinstitute a program of actively managing both vegetation and water levels in and around the artificial lake. When the dredge pond was first excavated, the surrounding terrain was characterized by extensive open areas and flats that mimicked natural salt flats and overwash fans. These areas were maintained by periodic draw down of the pond. These conditions provided highly favorable breeding and foraging habitat for the endangered piping plover.

In recent years, the Dredge Pond has expanded in size and vegetation has overtaken much of the remaining fringe area. Since its creation as a borrow pit for beach nourishment sand, storm tides have brought in silts and other fine sediments that have settled to the bottom of the pit and surrounding flats, causing water to perch and stagnate. The NPS should resume controlled draw down of the Dredge Pond during the winter months. This would expose the former flats areas to be used as piping plover breeding/foraging habitat in the spring and summer.

This, together with vegetation control clearly has the potential to assist piping plover recovery efforts by providing alternative nesting areas to the surf zone, where nests are dangerously exposed to storm tides and ghost crab predation.


These proposed actions are fully consistent with management activities undertaken in other areas of the seashore, most notably the part occupied by Pea Island Wildlife Refuge. It is perhaps ironic that the portion of the seashore set aside for wildlife is highly managed through activities to include habitat enhancement, extensive water control structures, water draw down, proscribed burning, and invasive species removal.  

By contrast, much of the seashore that was established in significant measure as a recreational asset has seen relatively little active management in the last decade or so, at least in terms of protecting wetlands and enhancing breeding and foraging habitat for an endangered shorebird species.  

The NPS and certain activist stakeholder groups need to acknowledge that the seashore, and the Cape Point area in particular, is not a pristine wilderness.  Rather, these areas have been heavily altered by human hand, mostly under auspices of the federal government. Given the man-made alteration to the interior Cape Point area, a continued abdication of active management responsibilities by the NPS can only lead to more environmental degradation and loss of recreational opportunities. 

The NPS is therefore called upon to immediately move to comply with terms of the NOV issued by the state of North Carolina over a decade ago and properly manage the wetlands along the Cape Point interior. The NPS is also called upon to resume active management of the Dredge Pond area through appropriate draw down and vegetation control measures.

Reasonable and prudent management of the Cape Point area on either side of the dune line will serve to both enhance the quality of the environment and ensure continued public access and appropriate recreational opportunities.

POSTSCRIPT

David Hallac, the seashore's superintendent, has said publically in interviews that he is pursuing solutions to the stormwater and flooding problems in the Cape Point area.

The state, Hallac says he was told, does not "permit" federal agencies to drain wetlands but would like to work with the Park Service on a plan for managing stormwater issues in the sensitive maritime area.

Hallac has also been in touch with the U.S. Army Corps of Engineers, which, he says, may have to permit any plans to park comes up with.

This winter, he said, seashore staff will continue to pursue the issue with the state Department of Environmental Quality and the Army Corps of Engineers.

There is no doubt that manmade structures -- from the dunes that were constructed in the 1930s to the Cape Point campground -- have changed the hydrology of the area. But correcting the problem is much more complicated than it might seem by such issues as state and federal laws and Park Service policies.

"I'm not promising anything," Hallac said, "because my guess is that this will become more complicated before it becomes clearer. But we're going to do our best to make improvements."

(Editor's Note: Chris Egghart is an environmental professional with 15 years experience in the Middle Atlantic and Southeast regions of the U.S. He has extensive experience producing natural resource management plans for federal agencies and is currently active in wetland restoration projects and compensatory mitigation programs for stream and wetlands impacts.)

  


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