An Architectural Design Approach to Climate Adaptation - Part 3 - How the land and water interact
Updated: Feb 17, 2020
Part One, The Only Constant is Change, describes how Planet Earth has looked significantly different over time, and how humans are now altering the planet at a more rapid pace than previously experienced. For instance, the coastlines of the world have varied greatly, with massive shifts in the sizes of ‘Florida’ previously making our coastline hundreds of miles wider, or much smaller.
A Gradual Shift
Five thousand years ago, when sea level was about 20 feet lower than today, there was no Biscayne Bay. Biscayne Bay formed as sea level rose to fill a depression in the limestone. During that time, sandy barrier islands, banks of carbonate sand and mud, and coastal wetland swamp and marsh deposits have grown and evolved. Especially critical was the relatively slow rise in sea level that occurred during the past 2,400 years, with less than 2 inches of increase in sea level per century. During that time, shallow sand and mud banks formed along the eastern margin of central Biscayne Bay and extended well across northern, southcentral, and southern Biscayne Bay, partitioning the bay into natural divisions.
Natural, unaltered Biscayne Bay was a magnificent, shallow subtropical estuary characterized by clear water and dominated by diverse and productive bottom communities of seagrasses and hard bottom soft corals and sponges. Mangrove wetlands rimmed the bay margin with limestone reaching the coast in only a few places.
The bays freshwater springs were visited by ships to get drinking water. The clear waters were maintained by the sediment filtering and trapping activity of the bottom communities of plants and animals and by coastal swamps. The benthic communities, in turn, were able to flourish because of the clear waters. Landward, freshwater sheet flow, natural tributaries, and shallow depressions that cut through the coastal ridge, fed water from the Everglades to the margins of the bay. Freshwater even entered the bay through springs in the limestone. Salinity channels and resulting freshwater upwelling affected the bay from the coastal cliffs to likely far offshore. The seaward margin of the bay was a series of sandy barrier islands to the north, channel-dissected shallow marine sand and mud banks along the central portion, and islands of an emergent coral limestone ridge to the south. Source: Discover Biscayne Bay
The Power of Nature
Other times nature-driven changes occur more rapidly, such as in large storm events. The Hurricane of September 1835 may have split what is now Virginia key apart from what is now Miami Beach, creating what is currently known as Norris Cut.
From 1903 to 1905, the human-made Government Cut dredging allowed for a more direct connection to the port and also split the tip-off of Miami Beach, creating Fisher Island. Additional dredging to widen and deepen Government Cut created fill to add land to the Port of Miami, and also created the foundation for the MacArthur Causeway in 1918.
Before the MacArthur Causeway was built, the Collins Bridge was the means to cross the Bay and was the longest wooden bridge in the world at the time of its completion in 1913. It was replaced in 1925 by a series of arch drawbridges and renamed the Venetian Causeway. The formation of this important corridor allowed for the construction of new islands within the Bay during the 1920’s Florida Land Boom.
A City of Islands
The 1920’s map below shows the much larger original proposal for Venetian Islands. Another causeway connecting Hibiscus Island with Di Lido, and then continuing North with five new islands was to be called ‘The Drive of the Campanelli.’ The foundation pilings for one of these islands is still visible peaking above the waterline.
In 1926 a two hundred forty-one-foot barge sank, blocking the mouth of the boat turning basin, and also the 1926 Miami Hurricane struck, marking the end of the Land Boom. The Shoreland Company responsible for the Venetian Islands went bankrupt in 1927 due to objections of “further mutilation of the waterway.”
An Altered Landscape
Right, this 1950 Map of the City of Miami has more similar resemblances to the coastlines and islands of Miami today. Dodge Island, Brickell Key, Treasure Island, and Margaret Pace Park are all still unbuilt and developed, showing how even after the objections for the Shoreland Company to stop building in the water, it still occurred. As a result of a century of modifications to hydrology, Biscayne Bay has changed from a subtropical estuary fed by coastal rivers, tidal creeks, and groundwater seepage, including submarine springs, to a pulsed system that alternates between marine conditions and extreme low salinity conditions near canal discharge sites.
Freshwater now enters the bay as an intense point source rather than as distributed input over time and space. Today, Biscayne Bay is an estuarine lagoon with salinity, circulation, and water quality that varies and is dependent on freshwater flow, wind-driven circulation, and ocean exchange.
The Desire of a Static Coastline
The native coastline with marshes and mangroves has been taken over by hard seawalls and private properties. The Natural Coastline, once affected by the daily ebb and flow of the tides, slowly changing as plants grew and died, and water levels rose and fell, is now a defined line, with exact measurement and coordinates able to be located within inches.
Even with endless miles of coastline, highly-desired weather, and beautiful views, there is not much public access to our bay for viewing, let alone to access into the water. Luckily in the last decade, a vocal push to develop a complete uninterrupted pathway along the Bay and Miami River has resulted in new sections of public access. Currently, projects are in development, and in the exploratory phases to introduce living shorelines.
The Army Corps of Engineers is exploring options for protecting our communities from Sea Level Rise. As a required part of their outreach measures, surveys allowed for participants to choose which adaptation measures they thought should be a priority. The top three, Mangrove Restoration, Restoring Coral Reefs, and Preserving Coastal Wetlands, can all be considered forms of Green Infrastructure. The Army Corp wrote on their official release of the survey results seen below, “while temporary flood panels came in a distant last place, we’d like to put in a quick plug for (admittedly boring) practical measures.”
Will We Learn From the Past?
As we have seen massive destruction of our Bay and water quality due to the decisions of the past, mostly including grey infrastructure, is it time that we reconsider what a ‘practical measure’ means to us in the face of the most difficult challenge our city has faced? Did the public not vote for the 'practical measures' because they were 'boring,' or perhaps because we have seen the damage that grey-infrastructure has caused to our ecosystems. The hospitality, recreational fishing, and commercial fishing industries compose a huge percentage of the South Florida economy. Without our beaches, marshes, wetlands, and Mangroves, those ecosystems will not survive.
Living Shorelines projects also have regulatory hurdles to tackle. The Department of Environmental Resources Management has had a strict policy on no construction going into the Bay, which has merit, as developers harmed the bay in the past through the construction of humanmade islands for their self-interest. Unfortunately, this policy has also hindered environmentally responsible projects from having a chance to help restore our natural ecosystems. As a result, landscape architects, planners, biologists, civil engineers, officials, and many others, have found creative means to introduce living shorelines into the south Florida landscape. One example was to leave an existing seawall in place and then to carve into the property, creating a secondary shoreline, and essentially a miniature island of natural habitat, a strategy FVS is utilizing in a living shoreline project currently.
Restoring What Was Removed
Living Shorelines can bolster grey infrastructure, attenuate storm surge and wave energy, enhance wetland habitat, sequester carbon, and protect from coastal inundation. According to NOAA, fifteen feet of terrain can absorb fifty percent of wave energy. Although not suitable for protecting against large storm surges, living shorelines are appropriate for mitigating the effects of tidal events, sea-level rise, and smaller coastal events. Green Infrastructure in the water and on the shoreline includes Constructed Wetlands, Artificial Reefs, Floating Islands, Constructed Breakwater Islands, Beaches and Dunes, and Living Shorelines, to name a few.
With so many leaders and experts of their fields, along with the publics resounding support for green infrastructure, it is time we leave the mistakes of the past in the past, and realize that we may need to build within the water yet again, however this time, not to create land for developers, but for our communities own survival and that of the natural habitat.