Modifying River-Floodplain Systems: A Historical and Ecological Perspective

Jaime Ashander

Kelly Gravuer

Megan Kelso

Mary E. Mendoza

Noam Ross

UC Davis REACH IGERT

AJY

Our Approach

The Question: What are the consequences of river-floodplain system modification?

The Case Study: The Napa River/Napa Creek Flood Protection Project

The Approach: Both historical and ecological techniques and perspectives

The Napa River/Napa Creek Flood Protection Project

Funding for plan passed in 1998

Provides flood protection for the City of Napa

Incorporates environmental objectives

Preserve habitats

Ensure water quality

Preserve geomorphic characteristics

A model for future projects?

Complementary modes of inquiry

Environmental History

Retrospective:

How did we get here?

Ecological Modeling

Prospective:

What will happen?

Understanding change through time

Complementary modes of inquiry

Environmental History

Retrospective:

How did we get here?

Ecological Modeling

Prospective:

What will happen?

Understanding change through time

History: Piecing together the past

Historians try to understand and explain change over time

Research is based on secondary and primary source material: Previously published articles and books

Archival documents

Photographs

Interviews

Environmental History: explores the human relationship with nature; how humans shape and are shaped by their environments

Making Organic Machines

Outline

Introduction

Environmental History

Methods

Context: River Modification in California

Settlement, Floods and Flood Control in Napa

Ecological Modeling

Hydraulic Model

Sacramento Splittail

Fremont Cottonwood

Social Consequences of Flood Control

Implications

Outline

Introduction

Environmental History

Methods

Context: River Modification in California

Settlement, Floods and Flood Control in Napa

Ecological Modeling

Social Consequences of Flood Control

Implications

Mining

Image provided by Oregon Historical Society

Isenberg, 2005; Mount, 1995

Panning for Gold

Sluice System

Photo provided by the Society of California Pioneers (ca. 1860)

Losing Autonomy

Individual Prospectors are forced to work as wage-laborers

Outline

Introduction

Environmental History

Methods

Context: River Modification in California

Settlement, Floods and Flood Control in Napa

Ecological Modeling

Social Consequences of Flood Control

Implications

Dredging the Napa River in 1889

Napa’s Vineyards

Fertile Land is not without cost…

Lake Hennessey: Created by Conn Creek Dam in 1944

Flood of 1955

Photo provided by the San Joaquin Library System

1975 Plan to eliminate the Oxbow

Forming a Community Coalition

San Francisco Bay Regional Water Quality Control Board

California Department of Fish and Game

State Coastal Conservancy

State Lands Commission

U.S. Environmental Protection Agency

National Marine Fisheries Service

Napa County Flood Control District

U.S. Fish and Wildlife Service

U.S. Army Corps of Engineers

Aerial photograph of 1986 flood

Napa River/Napa Creek Flood Protection Project

Provide flood protection

Restore the river’s natural flood modulation mechanisms

Improve water quality

Restore and provide habitat resources

Restore the floodplain

floodwall

detention basin floodwall

bypass excavation, floodwalls, and pump

station floodwall

terracingfloodwalls and pump

station

terracingterracing

terracing

South Wetlands Opportunity Area

Napa River/Napa CreekFlood Protection Project

Figure modified from U.S. Army Corps of Engineers Limited Reevaluation Report 2011

Napa’s Vineyards

Napa River/Napa Creek Flood Protection Project

Figure from U.S. Army Corps of Engineers Limited Reevaluation Report 2011

Project is predicted to achieve flood protection goals

$0

$50

$100

$150

$200

$250

$300

$350

1 in 2 1 in 5 1 in 10 1 in 50 1 in 100 1 in 200 1 in 500

Flo

od D

am

age (

Mill

ions)

Exceedence Probability

Pre-Project

Post-Project

Pre-Project Post-Project

100-year Floodplain

Outline

Introduction

Environmental History

Ecological Modeling

Hydraulic Model

Sacramento Splittail

Fremont Cottonwood

Social Consequences of Flood Control

Implications

Complementary modes of inquiry

Environmental History

Retrospective:

How did we get here?

Ecological Modeling

Prospective:

What will happen?

Understanding change through time

Our Approach

Hydraulic Model

Hydro-Ecological

Relationships

Population Models

Determining flooding patterns at different flows

How hydraulics/hydrology affect habitat quality and quantity

How changes in habitat through space and time affect population, according to life histories

Our Approach

Hydraulic Model

Hydro-Eco Relationship:Spawning

Habitat

Population Model:

Persistence

Hydro-Eco Relationship:

Recruitment/Mortality

Population Model:

Area × Timeof Adults

thewildlight.wordpress.com

SplittailCottonwood

Hydraulic Model: HEC-RAS

Model of Napa River developed by US Army Corps of Engineers

Used in design and evaluation of Napa flood control project

Hydraulic Model

Hydraulic Model: HEC-RAS

Model of Napa River developed by US Army Corps of Engineers

Used in design and evaluation of Napa flood control project

Hydraulic Model

Pre-Project

Post-Project

Topographic ChangeHydraulic

Model

Hydraulic Model: Outputs in SpaceFlooded Area and Depth at Flow of 20,000 cubic ft. per second

Pre Post Change

Hydraulic Model

Hydraulic Model: Outputs in TimeD

epth

(ft

)

Time (over one season)

Hydraulic Model

Outline

Introduction

Environmental History

Ecological Modeling

Hydraulic Model

Sacramento Splittail

Fremont Cottonwood

Social Consequences of Flood Control

Implications

Sacramento splittail

Pogonichthys macrolepidotus

Require floodplains

Endemic to SF Estuary

Separate Napa/Petaluma population

Found in project area

Sacramento splittail

Pogonichthys macrolepidotus

Require floodplains

Endemic to SF Estuary

Separate Napa/Petaluma population

Found in project area

(Stillwater sciences 2005)

Connecting hydraulics to persistence of splittail

Extend existing approaches (Ecosystem Function Model, Floodplain Activation Flow) We account for population-

level effects of habitat Enabling us to use

persistence as metric

Photo: DWR

Hydraulic Model

Hydro-Eco Relationship:Spawning

Habitat

Population Model:

Persistence

Hydro-Ecology

Relate flow to spawning habitat

Habitat requirements • Seasonal window• Minimum duration of

water on floodplain required for successful spawning and rearing

• shallow (<2m) areas must also be present

Hydro-Ecology

Relate flow to spawning habitat

Habitat requirements

Flow-depth relationships output from hydraulic model

Hydro-Ecology

Hydraulic Model

Relate flow to spawning habitat

Habitat requirements

=Habitat-Flow curve

Are

a o

f H

abit

at (

acre

s)

Flow (cfs)

Hydro-Ecology

Flow-depth relationships output from hydraulic model

Hydro-Ecology

Construct habitat-flow relations for pre- and post- restoration

Pre-project: Habitat vs. flow Post-project: Habitat vs. flow

Ha

bita

t a

rea

(a

cre

s)

Restoration can impact splittail habitat

Pre-project: Habitat vs. flow Post-project: Habitat vs. flow

Hydro-Ecology

Ha

bita

t a

rea

(a

cre

s)

Post-project, average year similar but good years more likely

Pre-project: Post-project:

Distributions of habitat areas

PopulationModel

Slight, but is it slight for the population?H

ab

ita

t a

rea

(a

cre

s)

How does the change in the distribution of habitat areas influence persistence?

= use of floodplain in lifecycle

AJY

PopulationModel

More floodplain habitat increased spawning success+ young-of-year survival

Young Juvenile Adult

Area

Surv

ival

PopulationModel

Flow Flooded area increased spawning success+ young-of-year survival

Flow

Are

a

= use of floodplain in lifecycle

AJY

Young Juvenile Adult

Fitted to Yolo Bypass flow and Suisun Marsh splittail counts

Yolo Bypass

SuisunMarsh

Napa

Sacramento

Davis

San Pablo Marsh

Suisun counts versus fitted

Area

Surv

ival

Flow

Are

a

Simulate persistence under pre- and post-project habitat scenarios Population

Model

Habitat

are

a (

acre

s)

AJY

Young Juvenile Adult

Suisun parameters Napa hydraulics

Results

Changed distribution of habitat area

(chance of decrease from 5000 to 500 adults based on 10,000 draws from pre and post distributions)

Changed distribution of habitat area greater chance of persistence!

But these results are sensitive to how we define “habitat”

Sensitivity of persistence to definition of habitat

Depth (feet)

Du

ration

(days)

Growth rates consistently higher post-project

Depth (feet)

Du

ration

(days)

Outline

Introduction

Environmental History

Ecological Modeling

Hydraulic Model

Sacramento Splittail

Fremont Cottonwood

Social Consequences of Flood Control

Implications

Cottonwood

Foundational species

Provide ecosystem structure, shading, and habitat

Populus fremontii

www.prbo.org

Cottonwood Modeling Approach

Focus on ecosystem function

Output Metric: area time occupied by adult cottonwoods

Explicitly track recruitment, growth, and mortality of trees to predict cottonwood habitat in space and time.

Test sensitivity across a range of 3 plausible life-history parameterizations

Cottonwood: Connecting Hydraulics to Recruitment and Mortality

Wate

r H

eig

ht

Rela

tive t

o S

urf

ace

Time

Land Surface

Water Level

Capillary Fringe

Surface must be moist but

not inundated during season

of seed availability for

seedlings to establish

Water must recede slowler

than seedling root growth

High water events

can dislodge

seedlings

Very high water events can

knock over saplings and

adults

Modified from Harper et. al. (2011)

Hydro-Ecology

Cottonwood: Model Structure

0 1Age 5+2 3 4

Saplings AdultsSeedlings

Scouring

water

height

Time

required

to drown

PopulationModel

1 m 2 m 3 m

30 days 60 days 90 days

Root

growth

rate

6 mm/day 2.7 mm/day 2.7 mm/day

Cottonwood: Model Structure

0 1Age 5+2 3 4

Saplings AdultsSeedlings

Scouring

water

height

Time

required

to drown

PopulationModel

1 m 2 m 3 m

30 days 60 days 90 days

1.5 m 3 m 5 m

60 days 90 days 120 days

Root

growth

rate

6 mm/day 2.7 mm/day 2.7 mm/day

12 mm/day 4.5 mm/day 4.5 mm/day

Pre-project(acres)

Pre-project 95%Confidence Interval (acres)

Post-project(acres)

Post-project 95%Confidence Interval (acres)

Medium 0.08 0 - 0.4 0.32 0 - 0.9

Cottonwood Results: Increase in coverage by adult cottonwoods

Total cottonwood population is predicted to be highly variable through time

Pre-project Post-project

Age class

AdultsSaplings

15

10

5

0

Acr

es

occ

up

ied

by

cott

on

wo

od

Year0 20 40 60 80 100 0 20 40 60 80 100

Single example trajectory

SignDecreaseIncrease

Change.01.02.03.04.05.06

Proportion of time occupied by adult cottonwood

.02

.04

.06

Cottonwood Results: Increase in coverage by adult cottonwoods

Pre Post ChangeMediumParameter Scenario

Pre-project(acres)

Pre-project 95%Confidence Interval (acres)

Post-project(acres)

Post-project 95%Confidence Interval (acres)

Medium 0.08 0 - 0.4 0.32 0 - 0.9

Low 0 0 - 0 0.005 0 - 0.4

High 5.8 1.6 - 11.6 13.4 7.6 - 19.3

Different parameterizations predict different absolute population levels

Pre-project(acres)

Pre-project 95% Confidence Interval (acres)

Post-project(acres)

Post-project 95% Confidence Interval (acres)

Medium 0.08 0 - 0.4 0.32 0 - 0.9

Directionality of change remains positive

Low Med High

Sign

DecreaseIncrease

Change

Combined results

Probability of Splittail

Persistence

Frequency-Adjusted

Acres of Cottonwood

Annual Flood Damages

($ Millions)

Outline

Introduction

Environmental History

Ecological Modeling

Social Consequences of Flood Control

Implications

Looking for Affordable Housing…

The Butler Bridge

Napa’s Riverfront

Housing

What we do know is…

Riverfront property value has increased

What we do know is…

Riverfront property value has increased

Napa still has an affordable housing problem

Making Connections…

1986 Flood

“Levees fail because they conflict with, rather than conform to, natural processes.”

Outline

Introduction

Environmental History

Ecological Modeling

Social Consequences of Flood Control

Implications

Expanding the Scope

Economics

net economic benefit

-making structures that support this distribution

Hydraulic mining

Expanding the Scope

Economics

net economic benefit

Environment

species, habitats, and processes

Hydraulic mining

Napa

Expanding the Scope

Economics

net economic benefit

Environment

species, habitats, and processes

ecosystem functions and services

Hydraulic mining

Napa

New ecological approaches

Expanding the Scope

Economics

net economic benefit

Environment

species, habitats, and processes

ecosystem functions and services

Equity

equitable distribution of benefits

decision-making structures that support this distribution

Hydraulic mining

Napa

New ecological approaches

The Future

Thanks! Carole Hom

Jim Sanchirico

UC Davis: Jeff Mount, Peter Moyle, Teejay O’Rear & Louis Warren

Napa County: Jeremy Sarrow

TNC: Jeff Opperman

USACE: Stanford Gibson, John High, John Hickey, Jeff Koschak

American Rivers: Mark Tompkins, Katie Jagt, Mary Matella

PWA: Elizabeth Andrews

Open Source Software: R + others

Baskett Lab

Today’s Speakers