PARKKIM

Making Mud Infrastructure

양화한강공원

Year of Completion: 2011

Location: Seoul Korea

Client: Metropolitan Government of Seoul

 

The Han River is 300 mile- long. Over its course it traverses the Western half of the Korean peninsula. Approximately 30 mile of the river flows within the boundaries of Seoul, at which point the River is nearly 0.6 mile wide. Before modernization, the Han River was the major venue for leisure, as well as of transportation in and out of the city.

Following the Korean War the Han’s cyclical flooding was seen as an impediment to industrialization development. The process of transforming its sandy riparian edge to concrete embankments began in late 1970’s. Today The Han functions as the major infrastructure for flood prevention in Seoul. There are dams and underwater weirs upstream and downstream of the city that control the water level, making it now physically impossible to bring back the historic riparian edge. Today the Han is as finely controlled as a bathtub, albeit a muddy one. Mud, carried down from the mountains by torrential summer rains, is deposited on the concrete rim of that bathtub, creating a yearly maintenance nightmare for the City of Seoul.

When the booming economy created new demand for an enhanced quality of life in the late 1990’s politicians started looking at waterfronts in Seoul. The crowning achievement of the period was the day lighting of the Cheonggye River. Once that project was completed, politicians set their sights on the Han. ‘The Han River Renaissance Project’ was laid out and executed from 2006 to 2011 with a total budget of approximately $600 million. The project was administered by the Seoul Metropolitan Government and included plans for six riverfront- renovation projects, including the Yanghwa Riverfront.

The Yanghwa Riverfront site is approximately 1.3 mile long and 330ft. wide, and located at the western end of Seoul. At the very beginning of the design process, the design team recognized that the concrete, triple-terraced condition of the existing riverfront was resulting in the visual and physical separation of people and the river and creating maintenance difficulties. During the monsoon season the water level in the Han rises enough that it inundated a significant portion of the riverfront with slow moving, mud choked water. As the water level drops again at the end of the monsoon, the flat terraces of the riverfront are left under a thick layer of deposited mud. Cleaning up that mud consumes an enormous amount of the Seoul Metropolitan Government’s money and manpower every year. 

Given the site conditions, we believed that re-tailoring the topography could be the key to improving the spatial experience of the waterfront and to more sustainable management. We transformed the stepped sectional condition into gentle slopes, ranging from 4% to 12% grade, by stretching out the existing retaining wall between the terraces. The design team performed extensive landform study on the site in cooperation with a hydro engineer in order to design a hydro-dynamic topography that helps the tidal mud to be swept easily back into the river when the water level drops. Since the riverfront is visible from the pedestrian bridge connection to Seonyudo Park, the design team tested many landform alternatives from different viewpoints to make the riverfront itself a scenic feature as well. The planar and sectional configuration of the riprap edge is intended to increase biodiversity in plan, the articulation of the edge condition creates more sheltering spaces for fish and other species. In section, a new ecology of plants has emerged from the mud layer deposited in the crevices of the riprap. Promenades at different elevations were created by delineating peripheries of landforms. They connect both ends of the park and enable young and old to reach the river’s edge without being hindered by steps or steep grades. Today people in wheelchairs or moms with strollers can easily access the edge of the river.

Observation on the patterns of usage at riverfronts in Seoul led us to keep the program as open as possible. People tend to use the riverfront as a space for relaxing and spending time, therefore we designed the topography so that it would function most efficiently as a mud-infrastructure, and allocated programs that would match the respective landforms with the minimum number of facilities. The park can be explained in three parts: Open Field, Wild Hills, and Riverine Theater. We expected the western side of the park, closest to the parking lot, would be the most populated area, needing space for active programs. To that end, we kept the existing soccer area a flexible Open Field. On the other side of the park, adjacent to another river that is known for its bird’s habitat, we designed an area that would be mostly visited by wild life. This area was given the most undulating topography with the least amount of pathways. We call it the Wild Hills. The Riverine Theater area, in the middle of the waterfront, is where the slope is the grandest in its length and width. Since the area is facing an island park, most of the culturally related events take place here with the slope acting as an amphitheater. To serve the program better, the existing concrete block edge was replaced with ‘Z-shape’ cantilever modules in order to create a spacious civic place right at the water. The diverse slopes now facilitate diverse activities and programs, by providing a dynamic relationship with the river. Amongst those slopes, some of the flat spaces were created as well. This was done by sculpting around parts of the mid level terrace. These flat spaces facilitate activities that require a leveled space.

After completion, statistics from the Seoul Metropolitan Government show that the annual maintenance expenses associated with mud removal at Yanghwa is only about 17% compared to another riverfront park nearby.

The newly articulated shoreline provides better habitat for fish, and has attracted a large variety of birds back to the waterfront. The riprap edge has performed to our specifications, providing an anchoring point for a variety of native and ruderal vegetation. Astonishingly, Evening Primrose is amongst the most common of the ruderal species to emerge from the riprap crevices, softening the landscape of stones and inducing other plants to grow.