Policies for a Rising Bay Project Technical Workshop May 5, 2015 - - PowerPoint PPT Presentation

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Policies for a Rising Bay Project Technical Workshop May 5, 2015 - - PowerPoint PPT Presentation

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The Policies for a Rising Bay Project Technical Workshop May 5, 2015 Welcome Introductions Review agenda Ground rules/guidelines Project Goal Collaboratively evaluate BCDCs fill policies in light of sea level rise and

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The

Policies for a Rising Bay

Project

Technical Workshop May 5, 2015

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Welcome

  • Introductions
  • Review agenda
  • Ground rules/guidelines
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Project Goal

Collaboratively evaluate BCDC’s fill policies in light

  • f sea level rise and develop guidance for the

Commission, staff and project proponents to promote shoreline resilience

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Steering Committee Members

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Case studies

  • Representative, hypothetical locations
  • Policies require projects be resilient to

mid-century of projected sea level rise and storms and adaptable to end-of-century

  • Opportunity to help develop guidance on

how to evaluate and phase grey to green adaptation actions

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Regional Context and Vision

Next steps to BEHGU

  • Baylands Ecosystem Habitat Goals Update (Sept

2015)

  • Sets recommendations for ecosystem resilience with

climate change

  • Guidelines for implementation, not a plan.
  • Need to integrate BEHGU with other factors and

constraints to create visions for a resilient bay

  • Calls for integrated visions/plans for segments of

shoreline

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  • The Bay and its shoreline are heterogenous
  • No one‐size‐fits‐all approach for SLR adaptation
  • Goal is to describe a range of options that are

feasible/appropriate in a given shoreline setting

Case Study Approach: Framing

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Bay Settings for Case Studies

  • Synthesized data to describe real Bay settings

(“shoreline typology”)

  • Limited dataset
  • Used coarse typology to create “hypothetical”

settings for case studies

  • Ultimately will develop more rigorous typology for

Bay adaptation planning and shoreline‐specific strategies

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Watershed Tidal Littoral/Bay

Climate | Geology | Topography & Bathymetry Watershed area Land Use Infrastructure Tidal Range | Fetch Wind Speed | Water depth Headland morphology QW (surf and GW) Qsed (coarse and fine) Stream power Tidal prism Wave power Fine sediment delivery Flow resistance Sediment trapping

Drivers Processes Land uses Shoreline Infrastructure Watershed sediment supply

Wave energy SSC

Bathymetry (mudflat)

Sed transport

Marsh width

(elevation, evolution) (Species)

Setting

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Watershed Tidal Littoral/Bay

Climate | Geology | Topography & Bathymetry Watershed area Land Use Infrastructure Tidal Range | Fetch Wind Speed | Water depth Headland morphology QW (surf and GW) Qsed (coarse and fine) Stream power Tidal prism Wave power Fine sediment delivery Flow resistance Sediment trapping

Drivers Processes Land uses Shoreline Infrastructure Watershed sediment supply

Wave energy SSC

Bathymetry (mudflat)

Sed transport

Marsh width

(elevation, evolution) (Species)

Setting

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Geomorphic Setting

  • Big wide alluvial valleys
  • alluvial fans/long plains
  • short steep plains
  • steep headlands/small valleys
  • steep no plain
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Baylands width

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Tidal amplification with SLR [From: Rusty Holleman and Mark Stacey, UCB]

Wave energy: Tidal Amplification, Wave heights

Incident wind wave heights [from: DHI 2013] [Coastal study from AECOM] [Tidal datum update from AECOM]

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Bathymetry

Mudflat width Wide (> 0.25 mi) Narrow (< 0.25 mi) Proximity to deep water

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Nearshore sediment transport

Nearshore sediment transport Depositional Dispersive Gyre

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Shoreline composition

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Erosion: 1 ‐ 4 m/yr Progradation: 1 ‐ 4 m/yr Progradation: >4 m/yr Shoreline evolution

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Watershed processes

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20 31 41 61 88 90 91 91 93 129 190 223 239 246 249 251 281 290 318 335 341 342 350 396 398 409 420 452 475 499 504 509 549

100 200 300 400 500 600 700 800 900 1000

Coyote Creek Guadalupe River Permanente Creek Sunnyvale West Old Alameda Creek Novato Creek Pinole Creek Sunnyvale East Alameda Creek Corte Madera Creek San Francisquito Creek San Lorenzo Creek Stevens Creek San Tomas Aquino… Napa River Calabazas Creek Wildcat Creek Matadero Creek Alhambra Creek Las Gallinas Creek Adobe Creek San Pablo Creek Rodeo Creek Walnut Creek Lower Penitencia Sonoma Creek San Leandro Creek San Bruno Creek Belmont Creek Colma Creek Petaluma River Lion Creek Coyote Creek Marin

Sediment Yield (metric tonnes/km2/yr)

Water Years 2000‐2013 HIGH MEDIUM LOW

20

Marin Co. Channels

Watershed processes: Sediment inputs

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Land use adjacent to Baylands

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Sea level rise projections

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Case studies

Case Studies 1 Marsh enhancement 2 Shoreline protection (Transportation) 3 Shoreline protection (Residential) 4 Shoreline protection (Airport) 5 Flood protection (Fluvial‐tidal flooding)

Characteristics Geomorphic Setting Bay SSC Wave impact (fetch, wind direction, water depth, wave height) Nearshore sediment transport Bathymetry (mudflat width) Shoreline composition Shoreline evolution Species considerations Marsh/Salt pond width Land use (mixed) Watershed sediment supply SLR Scenarios

  • 5 Hypothetical locations (You may recognize them)
  • Drawn from a “setting” or shoreline “type”
  • Issues that BCDC deals with regularly
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A diversity of vulnerable assets

Low‐income housing Tidal marsh Transportation structures (etc) Fluvial‐tidal interactions

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A diversity of settings…

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A diversity of land uses

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A diversity of possible actions and strategies

  • Drawn from BEHGU recommendations
  • BCDC permit analysts
  • Other reports (Leventhal, BCDC etc.)

Does not include:

  • Upland land acquisition for T‐zone
  • Strategic retreat
  • Many others…
  • Not a complete list!
  • Feel free to add/combine/phase
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Worksheet

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  • Walk through one example (brief)
  • After the break, we will split into our groups and

repeat this process for the 4 other case studies

  • Then we’ll report back

Example case study: Marsh Enhancement

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NAVD88

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Which to explore further?

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Worksheet

Riprap Low applicability: wide marsh, critical resources not near shoreline, wider area for natural solutions. NA NA

2

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Which to explore further?

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Ridgway’s rails

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Worksheet

Riprap Low applicability: wide marsh, critical resources not near shoreline, wider area for natural solutions. NA NA

2 Beach Medium applicability: eroding marsh, med wave energy with endangered spp., with high local sed supply. BUT dispersive, because of narrow mudflats, deep water

  • What is the life span of the strategy?
  • When should the strategy be implemented

and how much lead time is required?

  • Is the strategy adaptable over time and can it

be combined with other actions?

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Worksheet

Riprap Low applicability: wide marsh, critical resources not near shoreline, wider area for natural solutions. NA NA

2 Beach Medium applicability: eroding marsh, med wave energy with endangered spp., with high local sed supply. BUT dispersive, because of narrow mudflats, deep water, medium wave energy

  • What is the life span of the strategy?
  • When should the strategy be implemented

and how much lead time is required?

  • Is the strategy adaptable over time and can it

be combined with other actions?

Short term :

  • Mid‐century
  • Needs maintenance
  • Can be combined/phased
  • Move with adapting shoreline
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Worksheet

Riprap Low applicability: wide marsh, critical resources not near shoreline, wider area for natural solutions. NA NA

2 Beach Medium applicability: eroding marsh, med wave energy with endangered spp., with high local sed supply. BUT dispersive, because of narrow mudflats, deep water, medium wave energy

  • Is it constructable with existing understanding?
  • Cost‐effective?
  • Can it be permitted?
  • Impacts to the economy, environment, society,

equity?

Short term :

  • Mid‐century
  • Needs maintenance
  • Can be combined/phased
  • Move with adapting shoreline

‐ Difficult to permit? + Buildable with technical understanding + Protects and improves wildlife/habitat + Maintains infrastructure + Can adapt? + Cost‐effective + Nearby local sediment supply

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Worksheet

Riprap NA NA

2 Beach Medium applicability: eroding marsh, med wave energy with endangered spp., with high local sed supply. BUT dispersive, because of narrow mudflats, deep water, medium wave energy

Short term :

  • Mid‐century
  • Needs maintenance
  • Can be combined/phased
  • Move with adapting shoreline

‐ Difficult to permit? + Buildable with technical understanding + Protects and improves wildlife/habitat + Maintains infrastructure + Can adapt? + Cost‐effective + Nearby local sediment supply

3 High applicability: Wide marsh, proximal creek, high sed supply, Nearby open space

Reconnect creek to baylands

Low applicability: wide marsh, critical resources not near shoreline, wider area for natural solutions. Short and long term: Begin planning now, to build up marsh plain

+ Reuse of local sediment + Restores natural process + Marsh keeps pace with SLR? ‐ Difficult to permit [Flood control etc] ‐ Species considerations ‐ Contamination considerations

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M

Case study 1: Marsh Enhancement

Other ideas? Regional implications? Phased approach? Timing? Contingencies etc?

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  • Questions?
  • Time for a break. Then it’s your turn.
  • Thank you.
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