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EMERGENT ECOLOGIES OF THE BAY EDGE ADAPTATION TO CLIMATE CHANGE AND SEA LEVEL RISE

Summer Internship 2019 TABLE OF CONTENTS

Preface Research Introduction 2 Approach 2

What’s Out There Regional Map 6 AUTHORS Site Visits ` 9 Sarah Fitzgerald Section 11 Jeff Milla Plant Community Profiles 13 Yutong Wu

PROJECT TEAM Lauren Bergenholtz What’s Changing Ilia Savin Julia Price Impacts of Sea Level Rise 24 Nico Wright Marsh Migration Process 26

This publication financed initiated, guided, and published under the direction of CMG Landscape Architecture. What We Can Do

Unless specifically referenced all photographs and Tactical Matrix 29 graphic work by authors. Site Scale Analysis: Treasure Island 34 Site Scale Analysis: Bothin Marsh 46 , 2019.

Conclusion Closing Statements 58 Acknowledgments 60 Bibliography 62

Cover photo: Pump station fronting Shorebird Marsh. Corte Madera, CA RESEARCH INTRODUCTION BREADTH

As human-induced climate change accelerates and impacts regional map coastal ecologies, designers must anticipate fast-changing conditions, while design must adapt to and mitigate the effects of climate change. With this task in mind, this research project

investigates the needs of existing plant communities in the San plant communities Francisco Bay, explores how ecological dynamics are changing, of the Bay Edge and ultimately proposes a toolkit of tactics that designers can use to inform site designs. DEPTH landscape tactics matrix

two case studies: Treasure Island Bothin Marsh APPROACH

Working across scales, we began our research with a broad suggesting design adaptations for Treasure Island and Bothin survey of the Bay’s ecological history and current Marsh. We see these case studies as a thread uniting the research conditions. Beginning with the regional scale, we mapped the scales, drawing upon regional, meso, and site-scale information. historical shoreline, flood risks, shoreline conditions, ecologies, and operational landscape units based on underlying geology Over the course of the internship we also conducted five site and urban conditions documented in SFEI’s Adaptation Atlas. visits, which were crucial in informing our understanding of Bay This regional map informed our understanding of Bay-wide ecologies. We deeply appreciate CMG’s recognition that there is climate change challenges, and illustrates both typical and no substitute for experiencing a place firsthand. By allowing us to unique conditions along the Bay edge. test hypotheses on the ground and generate new questions from observed phenomena, the site visits proved to be invaluable to our Honing in, we next turned our attention to plant community research process. profiles of the Bay. By identifying individual species, their ecological needs, and the ecosystem services of each habitat type, we comprehensively outlined the appropriate uses of these plants in both restoration projects and urban settings. We created a catalogue of this information, organized by plant community, to quickly inform designers working on projects along the coast.

Zooming in even further, we next developed a matrix of landscape tactics for adapting the Bay edge to sea level rise (SLR). We applied the matrix to a set of sites, ultimately Above. Visualization of research approach 2 3 WHAT’S OUT THERE

CATALOGUING BAY EDGE ECOLOGIES & CONDITIONS montezuma

suisun slough Wildlife Area

Carquinez North

Novato honker bay A CHANGING BAY

pacheco creek past, present and future conditions

Gallinas gallinas creek Bay Point National Estuarine Carquinez South Research Reserve Pinole Walnut San Rafael

wildcat creek

Wildcat

Corte Madera corte madera creek

Point Richmond

channel

Crescent Richardson CENTRAL BAY

Golden Gate San Leandro

SHORELINE CONDITION Mission Islais

Historical Shoreline

Wetlands

Natural Shoreline (e.g., cli s, blu s) - Protected Shoreline (e.g., berm, levee, embankment) Visitacion

San Lorenzo FLOOD RISK

FLOOD ZONE san bruno canal 0’ SLR + 100 yr ood SHORT TERM SLR (2030) SOUTH SAN FRANCISCO BAY 0.5’ SLR + 100 yr ood LONG TERM SLR (2100) 2.5’ SLR + 100 yr ood

Eden Landing Ecological Reserve ENVIRONMENT MANAGEMENT Creek Colma San Bruno Operational Landscape Units

Subtidal bat ray island Tidal Flat Mowry Marsh San Mateo redwood creek As climate change and sea level rise continue to accelerate Lagoons

ravenswood slough at an alarming rate, the San Francisco Bay Shoreline must Developed Area San Francisco Bay begin adapting to changing conditions. The complexity of the “Bay edge” differs from to region and neighborhood to neighborhood. In order to fully grasp possible adaptation Belmont Redwood coyote creek strategies, we must understand past historical shoreline San Francisquito conditions, current conditions and future sea level rise scenarios in the short term and long term. 7 0 2 4 10 miles Stevens SITE VISITS SUISUN BAY SAN PABLO BAY

POINT SAN PABLO CORTE MADERA MARSH STATE MARINE PARK MILLER KNOX REGIONAL SHORELINE

ALBANY BULB BOTHIN MARSH

CENTRAL BAY TREASURE ISLAND CLIPPER COVE MARSH

MISSION CREEK PARK POTRERO POINT PIER 94 HERON’S HEAD PARK INDIA BASIN SHORELINE PARK YOSEMITE SLOUGH ISLAIS CREEK

FLOOD RISK

FLOOD ZONE 0’ SLR + 100 yr ood SHORT TERM SLR (2030) SOUTH SAN FRANCISCO BAY 0.5’ SLR + 100 yr ood LONG TERM SLR (2100) 2.5’ SLR + 100 yr ood

9 A COMPLETE TIDAL SYSTEM typical cross section through plant communities

11 PLANT COMMUNITIES OF THE BAY EDGE

Expertly adapted to local environmental factors like temperature, wind, salinity, soil type and moisture availability, the plant communities along the Bay edge boast a stunning diversity of species and ecosystem services.

As climate change tests the ability of these communities to adapt to new environmental conditions, designers working along the Bay edge are grappling with tough questions: is it responsible to plant native species knowing that climate regimes are changing? Would it be Subtidal Tidal Flat () Coastal Salt Marsh better to use species adapted to drier, hotter conditions farther south and begin transitioning local plant communities as climate change accelerates?

Through our interviews with native horticulturists and restoration ecologists, we have concluded that these well- intentioned questions should inform planting pallettes only sparingly. Climate change models, while crucial policy tools, are only models; adhering to their predictions too strictly could cause plant designers to cut the residency of some species prematurely, depriving them of the opportunity to adapt to new regimes. Rather than focusing on supplanting certain species, experts currently Brackish Marsh Coastal Grassland Ponds recommend creating large corridors that allow for natural species migration.

Landscapes have never been static. While these indigenous plant communities evolved for very specific conditions, they are also hardy and adaptable; with some help, many species may be able to adjust to the coming changes. Even if they don’t last 100 years or 300 years, they are still crucial for bees collecting pollen, for birds foraging on eelgrass and for marshes sequestering our carbon emissions today.

Coastal Beach & Dune Coastal Scrub Upland Managed Horticulture

12 13 SUBTIDAL

Zostera marina (Zosteraceae) Anas americana Clupea pallasii Ruppia maritima (Ruppiaceae) “Eelgrass” “American Wigeon” “” “Widgeongrass” Colonizes large areas with little other vegetation Feeds on herring eggs and eats eelgrass directly. Relies on submerged vegetation for eggs. Spawn provide Protected brackish areas. comingling. energy-rich food to birds that winter in the Bay. Supports the Bay’s last commercial .

Stuckenia pectinata (Potamogetonaceae) Phyllospadix torreyi (Zosteraceae) “Sago Pondweed” “Surfgrass” Suisun Bay. Fresh and brackish water. Rocky shoreline.

Key Benefits / Ecosystem Services Needs

Erosion prevention: traps sediment Light: penetration in the water column dictates the lower limit of eelgrass, while turbidity can cause dieback Wave attenuation Temperature: 10-20˚C, threatened by climate change High habitat value for birds, fish, invertebrates: basis for large marine foodchain Salinity: 10-30 ppt (parts per thousand) Water quality improvement: absorbs excess nutrients Substrate: 90% clay (0.001-0.0039 mm), silt (0.0039-0.625 mm) and sand Carbon sink: rough calculations show that the carbon sequestered by restoring (0.0625-2 mm) one hectare of seagrass corresponds to that of 10-40 hectares of dry-land forest

15 TIDAL FLAT (MUDFLAT)

Calidris mauri Hemigrapsus oregonensis Diatom Macoma Nasuta Western Sandpiper Mudflat Crab Micro Algae Bent Nose Mocoma

Key Benefits / Ecosystem Services Needs

Habitat value: cyanobacteria captures nitrogen and supplies bioavailable nutrients Slope: lower slopes and valley bottoms <500 m elevation in coastal waters Sediment supply: sediments move toward areas of weaker energy (tides usually carry Soil binding: cyanobacteria on the surface of the mudflat binds the mud, which sediment landward; waves usually carry sediment seaward) prevents erosion. Salinity fluctuation: rises with evaporation and falls with freshwater input from rain and Food provision: microorganisms contribute to the diets of shellfish and fish, which watershed benefits predators like water birds and shore birds Substrate: mud low in oxygen releases hydrogen sulphide, methane and/or ammonia Erosion control: sediment resevoir for marshes

17 COASTAL SALT MARSH

Distichlis spicata (Poaceae) Salicornia pacifica (Chenopodiaceae) Armeria maritima var. californica (Plumbaginaceae) Jaumea carnosa (Asteraceae) “Salt Grass” “Glasswort/Pickleweed” Sea Thrift “Marsh Jaumea” Excretes salt to adapt to saline Turns red in autumn

Juncus lescurii (Juncaceae) Spartina foliosa (Poaceae) Triglochin maritima (Juncaginaceae) Grindelia stricta var. angustifolia “San Francisco Rush / Salt Rush” “Cordgrass” “Seaside Arrow-Grass” “Marsh Gumplant” Produces a compound toxic to mammals if ingested

Key Benefits / Ecosystem Services Needs

Habitat value: acts as a nursery and refuge for many species of marine animals Slope: 1:40 ideal slope

Flood mitigation Salinity: generally 20-35 ppt; salinity fluctuates, while middle and upper marsh waters are often hyperhaline (above the salinity of normal sea water) Water quality protection: filters runoff Substrate: acid sulfate soils, occasionally with a greenish algal surface Erosion control: though prone to erosion from decreased sediment supply, can also attenuate waves and prevent upland sediment from being lost to deep water

19 BRACKISH MARSH

Schoenoplectus americanus (Cyperaceae) Bolboschoenus maritimus (Cyperaceae) Eleocharis macrostachya (Cyperaceae) Salix laevigata (Salicaceae) “Three-square Bulrush / Chairmaker’s Rush” “Alkali-bulrush” “Common Spikerush” “Red Willow” Formerly Scirpus robustus

Brackish marsh habitat typically occurs in the low- to mid-intertidal reaches of sloughs and creeks draining into the Bay, where vegetation is subject to tidal inundation diluted by freshwater flows upstream.

Juncus arcticus (Juncaceae) “Wire rush / Salt rush”

Key Benefits / Ecosystem Services Needs

Habitat value: SLR migration space for the baylands, especially for Slope: gently sloping lowlands only slightly higher than sea level and the tidal reaches of rivers and streams Water: tidal marsh ecotones above ordinary high tides are associated with Erosion control: buffer zone for the landward effects of tidal processes and the freshwater discharges from groundwater and surface flows bayward effects of fluvial and terrestrial processes, which helps control pollution, biological invasions and erosion Salinity: 10-18 ppt (in South Bay). Prolonged exposure (weeks) to salinity above 18ppt can cause dieback

Substrate: sand, silt and clay

21 COASTAL SCRUB

Artemisia californica (Asteraceae) Baccharis pilularis var. consanguinea (Asteraceae) Eriogonum nudum (Polygonaceae) “Californica Sagebrush” “Coyote Bush” “Buckwheat”

Lupinus albifrons (Fabaceae) Mimulus aurantiacus (Phrymaceae) Frangula californica (Rhamnaceae) “Silver Bush Lupine” “Sticky Monkey Flower” “Californica Coffeeberry”

Key Benefits / Ecosystem Services Needs

Groundwater table influence: prevents saltwater intrusion into groundwater Slope: lower slopes and valley bottoms <500 m elevation aquifers and deters saltwater and groundwater from moving inland/upland Salinity: tolerates higher salt concentration than upland plants due to exposure to Erosion control marine air

Soil: varies widely. Includes clay, shallow coarse soils and stabilized sand dunes

Note: can invade grasslands as the result of natural succession after the cessation of frequent fires

23 COASTAL GRASSLAND

Agrostis pallens (Poaceae) Deschampsia cespitosa ssp. holciformis (Poaceae) Festuca rubra (Poaceae) “Diego Bent Grass” “Pacific Hairgrass” “Red Fescue”

Iris douglasiana (Iridaceae) Leymus triticoides (Poaceae) Stipa pulchra (Poaceae) “Douglas Iris” “Creeping Wild Rye” “Purple needle grass” Formerly Nassella pulchra

Key Benefits / Ecosystem Services Needs

Carbon sink: can provide more reliable carbon storage than forests because they Slope: large areas are level, with other areas of slight slope that have high water are impacted less by droughts and wildfires infiltration rates, improving water storage

Habitat value: food and shelter for birds, mammals and pollinators Water: native perennials are drought-tolerant due to deep roots that capture, filter and store water, anchoring the soil in place long after the annuals die Erosion control Note: can be found directly upland of coastal marshes. Today’s grasslands are Note: Coyote scrub, introduced by grazing deer transporting seeds, threatens dominated by non-native annual grasses introduced by settlers. to take over grasslands near coastal ; trampling, livestock grazing and drought help protect grasslands from invasive shrubs

25 BEACH & DUNE

Abronia latifolia (Nyctaginaceae) Ambrosia chamissonis (Asteraceae) Atriplex leucophylla (Amaranthaceae) Fragaria chiloensis (Rosaceae) “Yellow Sand-Verbena” “Beach Burr” “Beach Saltbush” “Sand Strawberry”

Key Benefits / Ecosystem Services Needs

Habitat value: influences the intergradation with coastal scrub communities and Slope: found on exposed slopes near the ocean and stabilized lee slopes (areas provides habitat for insect fauna on the downwind side of ridges)

Erosion control Salinity: 1 ppt during the growing season and 10 ppt briefly following wave inundation Threat: perennial veldt grass. Native to South , if not controlled it is able to turn a dune scrub into a monotypic grassland in a short amount of time. Substrate: forms when a source of sediment delivers sand to rivers and ocean currents that ultimately deposit it on a receptive coastline

27 POND HABITATS

Spirogyra Stichococcus bacilaris Bacillariophyceae “Blanket Weed” A common green algae in salt ponds Diatom Algae Commonly found in freshwater habitats Found in the oceans, waterways and soils

Ruppia maritima Spatula clypeata Dabbling Ducks “Widgeon Grass” “Northern Shovelers” Group of duck species characterized by their preference for Submerged aquatic vegetation in bay area Forages head down in shallow baylands shallow pond habitats, feeding and flight patterns

Key Benefits / Ecosystem Services Needs

Water storage: serve as water retention ponds that store surface runoff during Salinity: varies seasonally by location, ranging from 15 ppt during the rainy periods of high tide season and 27 ppt during the late summer and early fall

Habitat value: feeding and resting habitat for waterfowl and migratory birds Sediment: varies, sometimes sierran type eolian sands; sediment traveling from the mouths of creeks reduces the sizes of lagoons, forming fringe marshes Erosion control Threat: susceptible to aquatic weed growth and algae bloom. Mechanical harvesting and adjustments to water levels reduce growing areas.

29 UPLAND MANAGED HORTICULTURE

Mission Creek Park Union Park Oakland Rocky Graham Park Marin City Bridgeview Park Foster City Rincon Park Miller Knox Regional Shoreline

Key Benefits / Ecosystem Services Needs

Carbon sink: offsets some of the carbon emitted due to construction Water: freshwater dependent

Urban shade Threat: salt water intrusion as sea levels rise

Protection from water and wind erosion: dense roots help control erosion by capturing and slowing down water from storms

Windbreaks and noise amelioration

Habitat value: pollinator food source

31 WHAT’S CHANGING

EFFECTS OF CLIMATE CHANGE ON BAY EDGE ECOLOGIES

33

century in response to the continued global warming with services such as septic tanks, landfills, and other waste increasing impacts on coastal regions. Sea level rise might disposal systems can be compromised and contaminate the only directlyTHE IMPACT impact OF coastal SEA LEVEL zones RISE but these areas are often the most densely-populated and economically active areas Sea level in the Bay has risen 8 inches in the last 100 years, (Nicholls, 2011b). Nichollsa rate that & will Cazenave likely accelerate (2010)in the next century. categorised The water level is expected to be 4ft above MHHW by 2030 under the the effects of sea levelextreme rise tide/SLR on coastal combinations zones scenario, into and reach two 6ft timeabove LAND SUBSIDENCE range categories: (i) short-termMHHW by 2100. effects such as submergence, increased flooding ofIn the meantime,coastal human land activities (inundation), such as filling land for saltwater development and pumping groundwater are causing land intrusion of surface water,subsidence and on thehigher Bay Area’s water shoreline, table; creating evenand more (ii) long-term effects thatrisk take to lives andplace property as along the the Baycoast edge. adjusts to new environmental conditionsPlant communities—particularly such as ecosystem the marshes—serve change, as our first defense against SLR, mitigating flood risks and mediating erosion, and saltwaterwind-wave intrusion energy. intoAs we aregroundwater. protected by marshes, Among they in turn need our help to adapt to climate change. these major biogeophysical impacts, inundation or coastal flooding, saltwater intrusion, and rising of water tables are highly detrimental to groundwater resources (Figure 2). Image source: Amira Jamaluddin, et al. (2016). “Threats faced by groundwater: A study in Kuala Selangor.” Stronger and higher storm surges are expected in Figure 2: Conceptual diagram of the impacts of sea level rise at relationship to rising sea levels, making coastal areas coastal aquifer area. (1) Higher sea levels promote stronger and susceptible to episodic and extensive marine inundation higher surge that lead to frequent inundation, which over time may become permanent and extensive; (2) The movement of saltwater- (Hay & Mimura, 2005; Ferguson & Gleeson, 2012). As freshwater interface landward and upward accelerates saltwater sea levels continue to rise, the coastal inundated area is intrusion; affecting the interface if the well is actively abstracted; translated inland with further encroachment of tidal waters and (3) Rise of water table disturbs underground systems (i.e. septic into and coastal river systems creates a condition tanks, landfills/open dumps, etc.) and may result in groundwater known as marine transgression. This can lead to damage of inundation at worst. Bulletin of the Geological Society of Malaysia, Volume 62, December 2016 67

35 MARSH MIGRATION PROCESS

Affected by Saltwater Intrusion

Migration Barriers Habitat “Squeezed”

Affected by SLR

Landward Erosion

Intrusion

High Marsh Migrate Upland Low Marsh Migrates to High Marsh Low Marsh Drowns, Transitions to Mud Flat Saline Groundwater

Salt Water

Coastal marshes naturally adapt to sea level rise by accreting sediment and migrating inland through a process called transgression. However, humans have developed land up to the edge of nearly every marsh; their habitat is squeezed between the developed edge, rising water level and landward erosion.

While SLR most directly affects marsh communities, saltwater intrusion will also impact plant communities in the upland zone. If we want to maintain the amount of marshes we have today, it’s crucial to provide suitable conditions by creating artificial inputs or migration space. 37 Petaluma Napa - 6 Sonoma REGIONAL MARSH MIGRATION 7 Suisun Slough 9

Montezuma Slough 10

Carquinez Salt Marsh Brackish Marsh Salt Marsh North Novato 5 8

Freshwater Marsh Brackish Marsh Gallinas 4 13 San 14 12 11 Rafael 3 Carquinez Bay Point Pinole South Walnut 15 Corte 2 Madera Wildcat Richardson 16 Locations mapped as suitable for migration were identified by isolating Point space preparation 1 17 East Bay Richmond Crescent undeveloped areas above the approximate elevation of today’s highest astronomical tide (z* > 1.34) and within the area expected to be inundated with 2.0 m of sea level rise, San Leandro as predicted by the Coastal Storm Modeling Golden System. Protected areas were identified 30 18 Gate using the 2017 California Protected Areas Database. Suitable areas are most prevalent Mission - 29 Islais in the North Bay, Suisun, and portions of the In order to save marshes, we need to think at a regional scale. In the future, areas of South Bay. saltwater-freshwater mixing will shift inland, impacting the highly diverse, highly productive Yosemite - 28 ecosystems in the Suisun and western Delta regions. The San Francisco Institute Visitacion (SFEI) has identified specific locations that are suitable for migration preparation, most of 19 San Lorenzo which are undeveloped areas expected to be inundated with 6ft SLR.

20 Alameda Colma - 27 Creek OLU boundaries San Bruno OLU bayward 21 Mowry boundaries 26 San Suitable for migration Mateo space preparation Land currently protected Belmont - 25 Land currently Redwood unprotected 24 San 5 miles N Francisquito Above. Biodiversity: changes along estuarine salinity gradient. Right. Image source: SFEI 5 km 23 22 Santa Clara 38 Valley Stevens 89 WHAT WE CAN DO

TACTICS FOR ADAPTING BAY EDGE ECOLOGIES LANDSCAPE TACTICS for adapting the Bay edge to SLR

Near-shore Reefs Mudflat Augmentation Reconnect Creeks to Bays Habitat Type Conversion rough baycrete structures (mixture of concrete, native sand dissipate wave energy; can help protect adjacent crucial to increase sediment regimes for marsh accretion and now possible for “habitat restoration” under the and rock, and oyster shell) marshes and other shoreline types. reservoir of freshwater supply to marshes and transitional ecotones. may BCDC Fill for Habitat Amendment case study: SF Bay Living Shoreline Project, Breuner Marsh sediment for marsh supply. USACE study coming soon. require breaching/removing flood control levees in their case study: Eden Landing case study: Seal Beach (Southern CA) tidal reach case study: Calabazas Creek

Submerged Aquatic Vegetation (SAV) Marsh Adaptation seeding eelgrass marsh spraying / water column seeding / offshore Enhanced Revetments & Riprap Beneficial Subsidence case study: Point San Pablo, Richardson Bay, Alameda sediment placement / marsh motors importance of heterogeneity in chemical makeup, texture, taking advantage of land subsidence of diked or Beach abstraction and recharge wells porosity, size, slope and wave exposure filled areas by converting to low-lying habitat case study: , restoration, case study: Seattle Sea Wall, Muscle Beach (East River, NYC) Hamilton Wetlands

Breakwaters Ecotone Levees Elevate Land Just Say No dissipate wave energy, can be designed as hard habitats 1:20 slopes or gentler, 1:30 ideal. case study: Power Station rejecting irresponsible projects, often from a critical case study: Living Breakwaters (NYC) between tidal marshes and flood risk levees. commitment to coastal retreat. greening up levees, not as long term as migration space case study: The Architecture Lobby statement on preparation (below) refusing work related to the militarization of the US- case study: Oro Loma Sanitary District Mexico border

Coarse Mixed Beaches Migration Space Preparation Stormwater Management less likely to erode while providing recreational value. can be hydrological connection essential for marsh migration; use runoff to irrigate and provide freshwater access as salt used in front of eroding marsh scarp, or fronting riprap. shell remove berms/walls/infrastructure that blocks flows. water intrudes hash, gravel, cobble regrading may be required. case study: Crissy Field Next marsh adaptation case study: Pier 94 Restoration Project case study: Rush Ranch Open Space Preserve, China Camp

43 MARSH ADAPTATION TECHNIQUES

1. MARSH SPRAYING 4. MUD MOTOR Sprayed from barges or pumped into marsh sprinklers. Placement and timing may bury marsh vegetation. Variable recovery time. Also known as “thin lift placement.”

2. WATER COLUMN SEEDING Sediment released into bayside channel enters the marsh with the tide. Timing constraint—must be coordinated with tides.

3. SHALLOW WATER PLACEMENT Sediment placed in shallow banks is carried in with tides. May bury subtidal organisms—possible food web effects. Appropriate for large sediment loads.

4. UPSTREAM MUD MOTORS Image source: SFEI & Stantec Semi-continuous motorized sediment dispersal ahead of the lowest downstream obstruction

45 SALTWATER INTRUSION BARRIER WELLS

Pumping freshwater into the groundwater aquifer prevents saltwater intrusion by raising the potentiometric surface area above sea level. This technology has been used in Los Angeles along 17 miles of coastline since the 1950s to protect coastal aquifers.

Very costly and energy-intensive, this technique should be used sparingly as a last resort. It could be applied to prevent salinization of brackish marsh soils and die-back of horticultural vegetation.

Image source: Water Replenishment District of Southern California, technical bulletin (fall 2007). 47 JUST SAY NO

As practitioners fundamentally tied to the business of building, we must ask ourselves when projects are appropriate to take on, and when we must commit to the collective project of retreating from vulnerable coastlines. The following questions should guide the project acquisition process on the Bay edge:

How soon will the site be flooded? How long will the intervention have a positive impact before another update is needed under current SLR projections? Is the window of time too small to design and construct an intervention?

How much will it cost? Weigh the cultural, economic and environmental value of the resource(s) in question against the financial cost. Is it a public project in question? If so, ask whom the project will benefit in light of who is paying for it; think critically about the burden of debt that will be saddled onto younger taxpayers who did not cause the problem nor make a decision to dig deeper rather than retreat.

Could this project be carbon positive? Marshes are among the best carbon sequestering ecosystems on the globe; even if a restored marsh is projected to become subsumed, it could still possibly sequester more carbon in its lifetime than the carbon emitted to construct the project. If the project is carbon negative and in danger of imminent flooding, discard it.

49 CASE STUDY: TREASURE ISLAND

Constructed with mud dredged from the Bay, Treasure Island’s history as a man-made island makes it unique among other urbanized areas. As a former military site that has been decontaminated through soil removal and capping, it is home to primarily horticultural plants while also hosting adaptive species (both native and invasive) along its riprap edges and neglected spaces.

5

2 3 6 1

4

Site plan Rip-rap Iceplant (Carpobrotus edulis), non-native

Submerged seaweed Beach plant community in Clipper Cove Communities behind bermed road Edge of southern Treasure Island 51 HABITAT TYPE EDGE ELEVATION : 9 ft TREASURE ISLAND man­-made island mhhw 6.3 existing condition managed horticulture mhw 5.6 mtl 3.4 mlw 1.1 mllw 0

POPULATION : 2,500 SLR RISK : HIGH *****

Flood 4ft 6ft

Ebb

LAND SUBSIDENCE 0.8’’/yr

DEVELOPMENT EDGE Rip-rap

Ebb Flood Elevation and datum data source: Google Earth and NOAA Datums for Yerba Buena 52Island. Population data source: 2010 Census. 53 [SLRSUBSIDENCE]

6ft SLR SUBSIDENCE

6ft SLR 9ft 4ft SLR SUBSIDENCE 4ft SLR MHHW 0ft 0

0ft 4ft 6ft Image source: NOAA Sea Level Rise Viewer, accessed August 2019.

Treasure Island is extremely vulnerable to sea-level rise due to its flat topography and the subsidence of its northwestern tip, ongoing since 1992. 0 Rip-rap cuts off the tidal connection to San Francisco Bay, leaving very limited habitat for coastal and intertidal plants.

55 TREASURE ISLAND MSL, 2019 homes on fill sinking ~0.8’’ per year

riprap with limited habitat value

Seawall

MSL 3.4’ FILLED LAND CONTAMINATED SOIL

YOUNG

The homogeneous riprap edge provides limited habitat value, supplanting the shallow tidal that used to occupy the spot FRESHWATER where the island now stands. While riprap does provide more habitat potential than smooth metal bulkheads, it nevertheless replaces bird SALTWATER foraging zones with a different ecology. Its over-use has shifted the overall species makeup of the Bay away from soft intertidal species compositions to more rocky intertidal zones usually found outside the Bay on the Pacific Coast.

Additionally, the homes created behind the recreational bermed trail are sinking fast; scientists have recorded the northwestern tip of Treasure Island sinking 0.8’’ per year over the last 20 years. 57 freshwater horticultural TREASURE ISLAND plants die off MSL + 4’ & 6’ SLR flooded homes behind berm

berm over-topping

+6’ SLR (9.4’)

Saltwater +4’ SLR (7.5’)

Seawall Subsidence

MSL 3.4’ FILLED LAND CONTAMINATED SOIL

YOUNG BAY MUD Intrusion

As sea levels rise, saltwater intrudes into former fresh groundwater zones. Higher groundwater could reach contaminated soils, mobilizing toxins. FRESHWATER Horticultural plants can usually only survive in soil salinity levels up to 2 ppt, while Bay water around Treasure SALTWATER Island oscillates between 11-29 ppt. This Monterey Cypress, for example, is not expected to survive once the fresh groundwater is compromised.

When tides bring water over the berm, the subsided land behind the trail acts as a bowl, flooding homes and absorbing the salts into the soil. 59 TREASURE ISLAND [DESIGN INTERVENTION] adaptation for SLR The fact that TI is an isolated, urbanized area without a large population permits more experimental approaches to address these issues. As sea level rises and land subsides, there is an opportunity to transform the northwestern portion of Treasure Island into a new ecological habitat. By breaking down the hard edge and creating gaps for tidal water to flow inland, communities like salt marsh and brackish marsh will gradually generate along the creeks as water levels rise. Upland plant communities can prevent erosion and act as wind breaks for the rest of the island.

Flood

Ebb Breakwater [INSERT 6’ SLR DIAGRAM] SALT MARSH

Sediment UPLANDS

DEVELOPMENT EDGE New Creek Rip-rap

BRACKISH MARSH

Ebb Flood

61 TREASURE ISLAND

tactical interventions portions of original fortified edge remain for erosion protection remove development

breached rip-rap wall allows for tidal action and ecological processes brackish marsh establishment

gentle bank allows for natural re-vegetation

+6’ SLR (9.4’) Brackish Marsh breakwaters +4’ SLR (7.5’) Salt Marsh NEW SEDIMENT

existing section cut YOUNG BAY MUD

Surrendering the development of the subsiding portion of the island is not only a cost-effective decision, but it SALTWATER also creates room for novel ecologies to colonize the area. Selectively breaking the rip-rap edge to reintroduce tidal action will bring back ecological processes that support fast-disappearing habitat. Living breakwaters will be used to capture sediment and enhance native features like eelgrass and oyster beds. These types of habitats additionally serve as carbon sinks. 63 CASE STUDY: BOTHIN MARSH

Bothin Marsh is located in a low-lying urbanized area that is already subject to flooding at high tides (nearly 30 times a year). The marsh is composed of 65 acres of mature, wide salt marsh habitat established near the mouth of Coyote Creek, supporting regionally rare plants and bird populations.

The site is highly accessible to the public via the Bay Trail, making it an ideal place for demonstrating ecological design concepts for sea level rise adaptation. Possible experimental projects could provide transition zones and make available space for salt marshes to migrate landward, as well as expand near-shore eelgrass and oyster beds to protect the marsh.

Highway 101 1 4 2 3 Richardson Bay

5

Site plan South Bothin Marsh, wave-eroded edges Coyote Creek, trestle bridge

Creek Culvert, water outflow to the Bay Overflow flooding onto roadways Brackish marsh in road swale View from Bay Trail Above. King tides. Image source: The North Bay Watershed Association (January 16, 2017). 65 Dog Park

BOTHIN MARSH LAND SUBSIDENCE BRACKISH MARSH existing condition Bay Trail Sediment DEVELOPMENT EDGE Mill Valley SALT MARSH (North)

COASTAL SHRUB EDGE ELEVATION : 8 ft SALT MARSH (South) Bridge mhhw 5.7 mhw 5.1 Sediment mtl 3.1 mlw 1.1 mllw 0

Coyote Creek SLR RISK : HIGH ***** Richardson Bay 4ft Bridge Flood 6ft

Ebb POPULATION : 10,735 Tamalpais-Homestead DEVELOPMENT EDGE Valley parking lot HABITAT TYPE mud flat BRACKISH MARSH salt marsh Highway 101 brackish marsh Elevation and datum data source: Google Earth and NOAA Datums for Yerba 66Buena Island. Population data source: 2010 Census. 67 [THREAT: SLR]

0ft 4ft 6ft

Image source: NOAA Sea Level Rise Viewer, accessed August 2019.

The Bay Trail, roads and flood control channels cut off sediment exchange between the watershed and the Bay. As sea level rises, the salt marsh on the edge will erode due to sediment loss. SLR furthermore threatens the marshes, and the Bothin Marsh and the Mill Valley-Sausalito Multi-Use Path (Bay Trail) will be severely inundated with 10 inches of sea level rise in 10 years.

69 BOTHIN MARSH MSL, 2019

Mill Valley Richardson Bay

bermed Bay Trail limits tidal action and sediment supply sediment from Coyote Creek blocked from reaching east marsh wave action eroding berm

sediment from Bay blocked from reaching west marsh

MSL 3.1’

WEST MARSH BAY TRAIL EAST MARSH

Built on top of a former railroad levee, the Bay Trail further severs sediment connectivity to the marsh. With only two small inlets and outlets, sediment transport is greatly reduced between the bisected eastern and western marshes, hindering the marsh’s ability to keep up with sea level rise. 71 BOTHIN MARSH MSL + 4’ & 6’ SLR

saltwater encroachment kills trees on nearby banks

drowned marsh converts to mudflat & open water berm over-topping, permanently flooded trail

[INSERT 6’ SLR DIAGRAM]

+ 6’ SLR (9.1’) + 4’ SLR (7.1’)

Bothin Marsh already experiences berm over-topping multiple times a year. With as little as +1ft of SLR, it will be too flooded to survive. Under +4ft conditions the entire system would convert to open water with little ecological value, and commuters will likely turn to more carbon- intensive means of traveling to work and school. 73 BOTHIN MARSH [DESIGN INTERVENTION] BRACKISH MARSH adaptation for SLR SAV Prepare gently sloping transition zone

Thin-layer deposits COARSE MIXED BEACHES FUTURE TRANSITION ZONE SALT MARSH Marsh motor Flood NEAR SHORE REEFS [INSERT DESIGN INTERVENTION DIAGRAM] Re-use Bothin marsh faces immense elevation challenges; we material for marsh suggest significantly elevating the Bay Trail on piles to eliminate the existing levee and allow for increased Bay Trail raised 4ft sediment exchange. Implementation of an upstream marsh motor and thin-layer sediment deposits from dredged material will also help alleviate the sediment deficit, raising the overall elevation of the marsh over time. While these interventions would bolster ecological processes within the marsh, they will also require near constant monitoring and sediment inputs, a costly proposition. Ebb Additional adaptation tactics include adding near-shore reefs, seeding aquatic vegetation and constructing coarse beaches to slow erosion, build up sediment banks and stabilize the marsh.

Finally, removing the landscaping supply store and businesses in front of Shoreline Highway would add 9 acres of upland space for the marsh to naturally migrate if keeping up with SLR proves untenable. 75 BOTHIN MARSH tactical interventions

elevated Bay Trail allows for free sediment flow and tidal action while making space for human use thin lift sediment placement and upstream marsh motor supply extra sediment to raise marsh elevation incrementally over time near-shore reefs and SAV attenuate waves and enhance habitat re-utilized berm material for micro-topography and marsh stabilization

6’ SLR 4’ SLR

sediment filled over time

existing section cut Elevating the Bay Trail allows for sediment exchange while preserving the social connection to the marsh and commuter routes.

Railroad berm material can be re-utilized to create micro-topographic changes within the marsh, complex landscapes that recruit high levels of biodiversity.

Studies show that marshes accumulate carbon 10x faster than the global average for boreal forests, and even as sea level rise converts marshes to mudflats, the captured carbon stays in the soil (unless disturbed). 77 CLOSING STATEMENT

Throughout this intensive project, we have come to appreciate the simple truth that adapting Bay Edge ecologies to rising tides is possible, but incredibly costly. Ultimately, we leave this project with more questions than answers:

How can we make collective decisions about which habitats to focus on?

How can we pool our resources to make regional decisions, rather than only disjointed local actions?

How can we ensure that socially vulnerable human communities can access these fast-disappearing natural wonders?

How can we move from designing at a discrete site scale to a regional level? Is this shift even possible in a paradigm of client-driven work?

We also recognize that landscape architects must become more proficient in our understanding of ecological processes and climate science in order to stay relevant as climate change accelerates. We humbly hope that this research contributes to this proficiency within CMG, and that it is useful in informing the firm’s future work.

78 looking south from the Pier 94 Wetlands 79 THE RESEARCH TEAM ACKNOWLEDGMENTS

YUTONG WU An enormous thank you to Nico Wright, Lauren Bergenholtz, Ilia Savin, and Julia Price. Your thoughtful framing, feedback, and provocations Yutong is originally from Guangzhou, China. With a strong interest in the were invaluable in guiding our research. We are grateful for your public realm and urban landscape, she is pursuing a MLA II degree at insights and energy throughout the process. the University of Pennsylvania. Having studied architecture for the first three years of her undergraduate studies at the South China University of Technology, she came to the conclusion that architecture alone cannot Thank you to Lauren Stahl, Greg Barger, Sam Woodhams-Roberts, tackle the recurring issues that face contemporary cities today. She Mike Hee, Matt Arnold, Ilia Savin, Lauren Bergenholtz, and Nico believes that the public realm is the key to advocate for positive change and Wright for taking the time to prepare us for and lead us on site visits. create unique experiences in urban life. The insights gleaned from these visits informed our work, led to many more questions, and enabled us to experience the magic of diverse Bay Area landscapes firsthand.

Thanks to CMG Landscape Architecture for the tremendous SARAH FITZGERALD opportunity to study the changing ecologies of the Bay edge. It has been such a privilege to have the time and resources to think critically Sarah Fitzgerald is entering her third year of the 3-year MLA program at UC . With deep familial roots in rural farming and experience and creatively about our agency as designers in our time. co-founding an urban garden in Madrid, Spain, Sarah is interested in food systems and how adaptation to climate change will shift food production in the built environment.

Sarah received her undergraduate degree from Providence College in Global Studies, a program that taught her the value of systems thinking and leaning into empathy. Her overarching goal is to use her creative energies to build a more socially just, ecologically resilient world that inspires wonder and joy.

JEFF MILLA

Jeff Milla is entering his 3rd year of the BArch program at the California College of the Arts. Born in San Francisco and raised in the Bay Area, he was able to see the vast changes in the built environment happening around him. Jeff is currently exploring materials consisting of fungus that can be incorporated into the built environment and the positive ecological impacts they may have.

80 81 REFERENCES DATA SOURCES

“San Francisco Bay Shoreline Adaptation Atlas” - SFEI & SPUR (2019) Historical Maps https://rumsey.geogarage.com/maps/g1032000.html “The Baylands and Climate Change: What We Can Do” - California State Coastal Conservancy (2015) San Francisco Watershed http://explore.museumca.org/creeks/1630-RescIslais.html “Strategic Sediment Placement in San Francisco Bay”-Jeremy Lowe of SFEI + Jamil Ibrahim, Amy Richey, Tom CancienneII, Tasmin Brown, and Craig Conner SF Bay Shore Inventory GIS Data https://www.sfei.org/data/sf-bay-shore-inventory-gis-data#sthash.DD0qk7Ih.dpbs “Selected Tidal Marsh Plant Species of the San Francisco Estuary: A Field Identification Guide” - Dr. Peter Baye for the SF Estuary Invasive Spartina Project (sponsored by CA State EcoAtlas Coastal Conservancy) https://www.ecoatlas.org/data/ https://www.ecoatlas.org/regions/waterboard/san-francisco-bay “Shoreline Plants: A Landscape Guide for the San Francisco Bay” - BCDC (2007) Operational Landscape Units (OLUs) “US Pacific Coastal Wetland Resilience and Vulnerability to Sea-Level Rise” - Karen Thorne https://www.arcgis.com/home/item.html?id=89e5326cd77141718b5e068ac6d1d672 of USGS (2018) WSU Students Design for SLR in San Francisco (2017) “Hard Habitats of Coastal Armoring” - Richard Hindle, UC Berkeley (2018) https://news.wsu.edu/2017/05/02/sea-rise-flooding-drought/

“Salt Dynamics in Coastal Marshes: Formation of Hypersaline Zones” -Chengji Shen, 2018 Presidio Native Plan Communities – article from Hohai University, China https://www.nps.gov/prsf/learn/nature/native-plant-communities.htm

“Estimation of Carbon Storage in Coastal Wetlands and Comparison of Different Management SF Plant Finder by Plant Community Schemes in South Korea” - Chaeho Byun and Shi-Hoon Lee, Yonsei University (2019) http://sfplantfinder.org/glossary.html#plantCommunities

“Carbon Stocks and Accumulation Rates in Salt Marshes of the Pacific Coast of Canada” - Tidal Datums Simon Fraser University with Parks Canada (2018) https://tidesandcurrents.noaa.gov/map/index.html

“Beneficial Use of Dredged Sediment to Enhance Salt Marsh Development by Applying a ‘Marsh Motor’” - Martin J Baptist, et al., Dutch publication (2019)

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