stream restoration in hamilton city: mission impossible?8 waikato river gully streams s 10 30 50 70...
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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
0
5
10
15
20
25
Nu
mb
er
of
site
s
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
0
2
4
6
8
Waikato River Gully streams
No
. nat
ive
fis
h s
pe
cie
s
10
30
50
70
Waikato River Gully streams
No
. of
inve
rte
bra
te t
axa
Invertebrates
Native fish
Tolerant invertebrates
Sensitive invertebrates
40 80 120 160Macroinvertebrate Community Index
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
U rb a n
Waikatostreams
Poor Fair Good Verygood
Pro
po
rtio
n o
f sa
mp
les
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
50
60
70
80
90
100
110
120
130
140
Jan Mar Apr Jun Aug Sep Nov Jan
Len
gth
(mm
)
Time 2007
Parana Park (P1)
Chartwell Park (K11)
Mangaiti Park (K10b)
Mangakotukutuku (M11)
P1
M11
K11 K10b
Average
(a)
0
5
10
15
20
25
30
Jan Mar Apr Jun Aug Sep Nov Jan
We
igh
t (g
)
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
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