After a week of working 12-hour days analyzing Charleston's flooding issues and talking with community groups, Dutch experts reaffirmed much of the city's ongoing efforts, but they also floated some new ideas.
Friday's presentation marked a milestone in the city's ongoing Dutch Dialogues — a year-long research and design program that started in the United States after Hurricane Katrina flooded New Orleans in 2005. Its guiding principle is that governments should deal with rising seas and flooding by embracing water instead of trying to build against it.
Mayor John Tecklenburg said the city hasn't advocated a respectful approach to water during its first 350 years, as settlers gradually filled in creeks and built over marshes. Instead, Tecklenburg said the city should consider the way water interacts with the landscape as it makes future planning, land use, development and redevelopment choices.
The process honed in on a few of the city's most problematic flood spots, and here is what researchers presented on each:
Andy Sternad a New Orleans architect with Waggonner & Ball, said Johns Island's greatest risk of flooding is due to storm surge. He said the city should ensure the safety of marshland and any new developments should include swales for water runoff.
Because of the different elevations on Johns Island, future development in areas 6 to 10 feet above sea level should be limited, and those structures should be elevated. Development in the 10 to 15 foot zone also should be elevated.
Sternad said Charleston should focus on conserving ecological assets on Johns Island. In the next three years, the city should consider creating an island watershed master plan and update its zoning and permitting processes. In the next three to five years, he said, the city should look to make infrastructure improvements.
In West Ashley, Dutch landscape architect Robbert De Koning said flooding issues are less a safety issue than an inconvenience, and the water problems there are due to poor planning.
The large area around the headwaters of Church Creek has become increasingly developed over the years, but the creek has not been wide enough to handle heavy rainfalls. The city recently razed 32 townhomes that suffered severe flooding three times in as many years.
De Koning said the city should develop a integrated water management plan for retaining, storing and discharging water. De Koning also said homes in the extended flood plains should be elevated.
On the peninsula, Dutch architect and urban designer Frits Palmboom said the Low Battery should be raised to the height of the High Battery — a project the city already has been working on.
He also said city leaders should consider fortifying a perimeter around the peninsula, using Lockwood Drive as a wall to prevent flooding.
In the port area along the Cooper River, Steven Slabbers, managing director of one of the Netherlands’ leading landscape architecture firms, said city leaders should consider installing a levee system east of East Bay Street. The Waterfront Park area should also have a sea wall.
Along the Ashley River, he recommended the city pursue one of two options: either a levee along the existing river's edge or one farther out into the marsh.
In the city's Medical District, a greenway should be extended toward Ashley Avenue. Cherry and Bravo streets should have access to the Crosstown Expressway, and the currently four-lane Hagood Avenue should be reduced to two lanes and be elevated as it gradually meets with the new development in WestEdge.
As far as WestEdge's current plan to cover Gadsden Creek as part of reworking drainage for new development, Slabbers said the creek's existing pollution does need to be addressed, but it should not be covered. The creek is currently influenced by tidal movements.
On the east side of the city, with the increasing likelihood of "rain bombs" — storms with sudden, intense rainfall — leaders should try to slow water as it moves from the higher ground toward the harbor.
Waggonner & Ball architect Ramiro Diaz recommended the city research the use of permeable pavers, try to plant as many trees as possible, and install more underground water storage pipes similar to the brick archways built under parts of the city in the mid-19th century.
A final Dutch Dialogues report is scheduled to be presented in September.