Stream restoration in Hamilton City:Mission Impossible?

Cities are where most people interact with biodiversity most often

Hamilton City streams

>120 km of mapped gully stream

Impacts are complex – multiple stressors

Effects of stormwater on hydrology

Flashier flows & bigger floods

More bank erosion

More sedimentation

Warmer water temperatures

Higher levels of contaminants

Storm runoff can occur 10 times more oftenTypical large floods can occur 3 times more oftenTemperatures can be around 6oC warmer

http://www.uprct.nsw.gov.au/

Historical legacies…

…such as old landfills

Urban intensification and periurbandevelopment…

…sediment inputs

Channelisation…

…accelerates drainage

…homogenises habitat

Barriers to fish passage

45% of culverts can be barriers to native fish movement in Hamilton City…

Fish in Hamilton streams

Threatened native species – 4 spp

Introduced species – 4 spp

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Common bullyRedfin bully

Non-threatened native species – 5 spp*

*

*

* ** * *

*

* = migratory

Pest fish…

• Catfish

• Gambusia

• Koi carp

Numbers typically low in city streams

animal.discovery.com

Longfin eel

THREATENED

THREATENED

Giant kokopu

Torrentfish

THREATENED

Torrentfish

Inanga

(Photos: Stephen Moore, Landcare Research)

Common bully

Banded kokopu

Torrentfish

Torrentfish

THREATENED

Inanga - whitebait

THREATENED

Inanga

Eels

Hamilton

Distance travelled> 110 km

Distance travelled 5,000 km

The great migration

Natal originBanded kokopu

Banded kokopu

Source: B. David, Waikato Regional Council

Banded kokopu

Hamilton

Giant kokopu

Inanga

To restore kokopu populations in city streams need to manage natal habitats in riverine lakes

Urban gully streams are important for biodiversity

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Waikato River Gully streams

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Waikato River Gully streams

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axa

Invertebrates

Native fish

Tolerant invertebrates

Sensitive invertebrates

40 80 120 160Macroinvertebrate Community Index

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U rb a n

Waikatostreams

Poor Fair Good Verygood

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Macroinvertebrate Stream Health Index

Most urban streams are in “poor” condition, but some sites are “fair” or better

First step is to protect remaining good sites

Mangakotukutuku Stream trib.Sandford Park

Opportunities for restoration…Protect keys habitats

…disconnected from stormwater network

…30% of mayfly and caddisfly species in city

…uncommon, iconic, even new invertebrates

from McCraw 2011

Opportunities for restoration…Improve water quality

Councils:• Raise public awareness• Stormwater treatment

• sump filters• detain, infiltrate,

evaporate• Greenfield developments

vs. established residential areas

Landowners:• Keep chemicals out of drain• Clean cars on the grass• Keep rubbish out of gully/stream• Paint zincalum roofs• Disconnect downpipes if roof-

cleaning etc

Before 4-5 years later

Opportunities for restoration…Riparian planting

Opportunities for restoration…Enhance instream habitat

Tuna townhouses

Kokopu condo

Wetland creation

for mudfish

Before

During

After

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Jan Mar Apr Jun Aug Sep Nov Jan

Len

gth

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Time 2007

Parana Park (P1)

Chartwell Park (K11)

Mangaiti Park (K10b)

Mangakotukutuku (M11)

P1

M11

K11 K10b

Average

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igh

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Time 2007

(b)P1

K11

M11

K10b

Average

Opportunities for restoration…Re-introduce fish

Giant kokopu

Evidence to suggest pheromones needed to attract new recruits

Opportunities for restoration…Passage and connectivity

Fish passes in Hamilton…

wceet.org.nz/

Before

During

After

Fish pass construction –Peacockes Rd

Inexpensive solution to provide passage for banded kokopu

Photo: Bruno David

Opportunities for restoration…Exclude pest fish

Photo: John Gumbley

Manga = streamkotukutuku = tree fuchsia

www.streamcare.org.nz