Druppel 16-3 - Dispuut Watermanagement

From the editors
Volume 16, Number 3, June 2006
The ‘Druppel’ is a magazine of the
student society of water management
of the TU Delft. The magazine is
published four times a year.
Editors
L. Valkenburg and M. van Ginkel
In cooperation with:
Cees Kamphuis, Harry de Brauw, Ruud
van der Ent, Caitlin Pilkington, Jair
Smits, Benjamin Fischer, Erik Liefting,
Sigrid Scherrenberg, Pieter Bol, WISST.
Lay-out
Jaïr Smits
Printing
Koopman & Kraaijenbrink
The ‘Druppel’ is distributed to
all members of the
Dispuut Watermanagement
Faculty of Civil Engineering
and Geoscience
room 4.74
Stevingweg 1
2628 CN Delft
7HOHSKRQH
E-mail
dispuut.watermanagement@ct.tudelft.nl
Internet
www.dispuutwatermanagement.nl
The new board has been installed. Our
new chairman Cees Kamphuis has written
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This is followed by the introduction of
the new board on pages 6 and 7.
The succesful symposium last april is
described on pages 8 and 9. Marloes van
Ginkel gives an update of the situation
on the educational front at pages 10.
7KH UHSRUWV RI WKH ¿HOG SUDFWLFDO LQ
Luxembourg and the excursion urban
watermanagement can be found on
pages 11-14.
Jair Smits tells about his fourthyears
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an 16. This is followed by the report of
Benjamin Fischer from Tanzania on page
17.
Druppel 3 - 2006
Colofon
Hi all!! This is already the third druppel
of the year 2006. This fresh new edition
contains all the news and information
about the activities of the student society
of water management.
The interesting master thesis of Erik
Lieftink, an article written by Sigrid
Scherrenberg on green roofs and Pieter
Bol’s contribution ”Water for Benin” can
be found on the pages 18-23.
This druppel ends with a dramatic story
about Suriname on page 26.
Enjoy reading!!!
Greetzz Marloes & Leon
3
Table of contents
Table of contents
Druppel 3 - 2006
From the editors
Table of contents
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A fresh new board
Symposium Urban Watermanagement
Education
Field Practical Luxembourg
Excursion urban watermanagement
)RXUWK\HDUVSURMHFWLQWKH3KLOOLSSLQHV Internship in Tanzania
Master thesis Erik Liefting
Green roofs
Water for Benin
Aid for Suriname
Sponsors
3
4
6
8
10
11
13
17
18
20
23
26
27
Sponsor index
KIWA
HKV
FLYGT
WL Delft Hydraulics
VEWIN
Waterschap Rivierenland
+RRJKHHPUDDGVFKDSYDQ'HOÀDQG
4
2, 27
27, 28
27
27
27
27
From the board
From the board
Cees Kamphuis
This is not only the time for the barbeques and swimming in the ‘Delftsche
hout’ but also for a lot of activity at the
Dispuutshok. The symposium committee
remembers with pleasure the interesting symposium about Urban Watermanagement, the GVR-committee is doing a
good job in preparing the trip to Vietnam
and lots of members are still busy with
uitbuiken after the Watermanagement
Barbeque.
A group of 20, mostly watermanagement,
students joined the Hydrological Fieldwork this year. In my opinion this was a
week with lots of hard work, but also with
lots of fun. I really think this was a tremendous week with a lot of integration
between the Dutch and foreign students.
It is a beautiful opportunity to perform
hydrological measurements and research
by yourself. So, when you’ve got the opSRUWXQLW\WDNHSDUWLQWRWKH¿HOGZRUN
Druppel 3 - 2006
Meat, burnt meat…. I can’t stand it anymore… Normally the combination of lots
of food and my stomach don’t make any
trouble, but with this number of barbeques even the biggest carnivore has
to surrender. This is actually quite good
news, because it tells us something about
the tremendous weather: it’s summer!
Finally, I want to wish luck to all of you
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holidays.
A fresh new board
A fresh new board
Harry de Brauw
As you probably know, the Water
Management Board exists out of 6
members. Each half year three members
are thanked and dismissed for their
dedication for the Water Management
Dispuut. I would like to thank Ronald
Bothé, Marjolein van der Kraan and Jair
Smits for their continuous effort during
one year for the Dispuut. They are now
replaced by:
Druppel 3 - 2006
Floor van de Berg van Saparoea Treasurer
Harry de Brauw –
Commissioner of Companies
Ruud van der Ent –
Secretary
Meanwhile, three of the old members
have taken the following positions in the
board:
Maarten van Dieren –
Commissioner of Students
Marloes van Ginkel –
Commissioner of Education
Cees Kamphuis –
Chairman
As one of the new board members, I
was assigned to write a contribution for
“De Druppel”. “Introduce yourself” is the
guideline for this text…
As a small boy I was carried and pushed
around through the great ranges of the
Alps. My parents couldn’t know that these
6
weeks in summer and winter would be of
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least until now). Everyone participating
in water management has probably built
dams in creeks and what used to look like
enormous rivers with their rapids. So did
, DQG , ORYHG LW $JLQJ FDPH WRJHWKHU
with a slight shift of interest, maybe it’s
better to say: “a widening of horizon”.
The enormous peaks pointing in the sky
around me started to attract me. Hiking
and doing the water management game
in rivers was no longer satisfactory.
These ridges, faces and snow covered
summits had to be climbed! This started
with a course into mountaineering at the
age of 16 and became an increasing time
consuming hobby during the years to
come. After high school, I left to study
for one year at the University of Colorado
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my interest in climbing which I tried to
combine with my study civil engineering,
the last sometimes suffering from the
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engineering at the TU Delft and became
a member of the “Delftsch Studenten
Corps”. Civil engineering couldn’t cause
me to be very enthusiastic for this
subject in the beginning. I preferred to
travel and climb as much as possible.
Nowadays things changed, sometimes I
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on a tiny ledge at an altitude of over
PHWHUV EXW ZDWHU PDQDJHPHQW
has caught my attention. My climbing
partners are complaining: “You do not
join us anymore on all the trips abroad”.
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summer is still holy for me, the perfect
time to climb the Alps….. I won’t make it
A fresh new board
Ruud van der Ent, our new secretary, is
the youngest of the team. He managed to
go through his study within the nominal
time period. He is moving to Delft this
week.
Floor van den Berg van Saparoea, our new
treasurer, is also known at the mechanical
side of the faculty, you can sometimes
¿QG KHU OHFWXULQJ &7 0HFKDQLFV RI
Systems. She is an active member of the
“Delftsch Studenten Corps”.
Druppel 3 - 2006
to Vietnam this summer.
7
Symposium
Symposium “Urban Water management“
Pascal Kregting.
This article should be completely obsolete,
because everybody from the section was
there. For the folks who were not there
and maybe are feeling a bit of guilt this
article will give you a short summary of
the day.
Druppel 3 - 2006
8
Nowadays water quantity and water
quality are both important to the
European water household. The aim of
the symposium was, and still is, to give an
innovative view on the current research
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management.
With loads of coffee being served in the
early morning, every participant had the
chance to be completely awake for the
¿UVWSUHVHQWDWLRQ
The chairman Frans van de Ven started
the day with an introduction and made
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the people from the board who had a
party the day before).
Rutger de Graaf from the TU Delft started
the sequence of presentations with one
about innovative concepts for urban
design. With a nice smile and keywords
like vulnerability and the principle “Closed
City” he moved the audience.
After his presentation it was the turn
to Aad Oomens from Grontmij. While,
unfortunately, I was not present at his
presentation I heard the “ooeeeesss”
and “aaaaahhhs” from far away. I think
this means that it was very interesting,
because the topic was about sewerage.
Mrs. Katheleen Poels from DHV was next
in line. She could not wait to start the
presentation and she was completely
right. The topic about groundwater
problems was well chosen and she made
the audience hers, especially during the
questions session.
Because of chances to get a brain
RYHUORDG WKH FDEDUHW ZLWK WKH ¿WWLQJ
name “Abracadabaret” started halfway
during the day. With a satiric, dry Dutch
humor they made sure that the minds of
the participants where on the subject,
but not in a serious way.
Because people were tired of laughing
all the time, it was the right time for the
lunch break. With the information from
all the presentations and the cabaret
people had enough to talk about while
WKH\ZHUHQRW¿OOLQJWKHLUVWRPDFKVZLWK
the excellent lunch.
Then our guest from the United Kingdom,
David Butler from the University of
Exeter, gave a presentation with the
title “water sustainability: a journey into
the unknown”. My compliments for the
perfect English and of course for the
nice presentation. Now I will think twice
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After a small break and some discussion
it was the turn to Rob Nieuwkamer from
Witteveen+Bos to make the audience his.
With a short but interesting presentation,
he emphasized the working together
with non-technical people like architects
and he made an introduction for the
case about the water management plan
Dordrecht.
Should we built our cities for twenty years
or for centuries? There were some good
discussions, and in the end, both visions
turned out to have pros and cons.
The day was coming to an end for all the
participants and after some drinks all the
participants had to leave. The day for all
the speakers and the organization ended
with a glass of beer in the hand and some
nice conversations about everything and
nothing.
Druppel 3 - 2006
Symposium
9
Education
Education
Marloes van Ginkel
Maarten doesn’t want to waste one
of his opening sentences to me; so I’ll
start my article about education in a less
interesting way.
Druppel 3 - 2006
10
The educational system of our master
has changed. We are working with
‘blokvakken’ nowadays. This means:
a change from lectures to integrated
OHVVRQV ZLWK PRUH SUDFWLFDOV ¿HOGZRUN
and information from company experts.
The idea is that this will improve the
educational system and prepare the
students better for their future work.
The change was sometimes successful
and sometimes less successful. A lot of
feedback from students and teachers is
used to evaluate the courses and to think
about improvements for next year. Thank
you for your help.
The results from the questionnaires
and the agreements I made with the
teachers for next years courses will be
put on Blackboard. The courses that are
evaluated last year are: Water Quality
Management, Drinking Water Treatment,
Civil Engineering in Developing Countries,
Operational
Watermanagement,
Wastewater Treatment, Ecology, Irrigation
and Drainage, Biogeomorphology, Polders
and Flood Control and Hydrological
Measurements.
I want to emphasize that feedback from
students is very important, without your
help we cannot improve the courses. Fill
in the questionnaires and hand them in
at room 4.74. And, when you want to say
something about a course, please come
to me.
Field Practical Luxembourg
Field Practical Luxembourg
Caitlyn Pilkington
The week consisted of a typical day of
rise at 7:30 to arrive at the table with
the aim of consuming as much bread
as possible to ensure adequate fuelling
for the mornings work. Make another
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student/supervisor, gender and general
Dutch-ness), pick up some equipment
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climb into.
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at different locations in streams in the
Wark river catchment. We all enjoyed the
YDULRXV VWUHDPÀRZ PHDVXULQJ JXPERRW
wearing, rainfall catching, weir measuring,
tracer seeking, dam observing, theodolite
posing and of course, macrofauna hunting
activities throughout the eventful week
of experiments. Not to mention the treeclimbing, dancing, swimming, singing,
poetry writing and grass tumbling. Upon
completion of the above activities then
it must be time for an outdoor lunch,
after which we daily enjoyed the uitbuikmoment, followed by the inkak-moment,
by which time there were no excuses left
and no dishes to clean anyway so back
to work.
Druppel 3 - 2006
On the morning of Friday 12th May, 20
eager young hydrology students arrived
bright and early at the TU to commence
WKHLU ZHHNORQJ K\GURORJLFDO ¿HOGZRUN
course to Luxembourg. It was to be their
most well-rested moment in the next
seven days – even for Marloes who had
arrived directly from a party.
11
Field Practical Luxembourg
Druppel 3 - 2006
Finally back to camp in the afternoon to do
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a laptop to enter data onto, sieve some
sand, take a siesta, drink beers, or plan
the evenings menu with the impressive
per-tent ‘survival kit’ bestowed by the
organised Gerda. Work, eat, consume
another beer or four in the name of
hydrological research, perhaps some
ODQJXDJH OHVVRQV WKH PRVW SUDFWLFDO RI
my Dutch was learnt in these later hours)
and eventually, sleep. We enjoyed some
impressively close thunderstorms from
our thin tents on some of those nights,
though it didn’t rain in the daytime, much
to the dismay of our very own team of
Rainiacs.
A trip to Luxembourg city on Saturday
night ended in disaster as Martin put too
much faith in his onboard GPS system and
arrived in Luxembourg city…. 40 minutes
after he had left it.
Well, by the third day on a diet consisting
predominantly of sandwiches, the
Chinese had had enough and demanded
the right to eat cake for lunch from that
day forward. This opened up the door for
experimentation from all cultural sides
and by the next morning, even the Dutch
12
were happily pouring olive oil and salt
onto their bread.
On the last day, each group presented
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over, presentations followed.
Notable achievements included the ‘relax’
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ring, Ana’s very own Olive oil trophy,
Raheena’s roll of packing tape to prevent
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with-sandals look. One particular prize
was to be shared amongst almost every
member of the trip during the barbeque
that followed. The week was topped off
by a soccer game and by a BBQ with a
vast array of delicious foods, beginning
at 6pm and lasting until the last sausage
was cooked at around 1. The entire
group bonded through the old Australian
tradition of donning outrageously bright
makeup while sharing food around a BBQ.
I must say that Mr Luxembourg and Mr
Baptist looked particularly fetching with
their cheeks highlighted, and that purple
shadow for the eyes is really their colour.
So a big thankyou to everyone involved in
organising and running the week, it was
thoroughly enjoyable, and great to get
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Excursion Urban Watermanagement
Excursion Urban Watermanagement
Marloes van Ginkel
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we visited Gemeentewerken Rotterdam.
They have developed a very sophisticated
solution for their rain water problem; a
storage reservoir of 10.000 m3 under
D YHU\ ODUJH SDUNLQJ JDUDJH &RVWV million euro.
Our last excursion of this day was to
IJburg near Amsterdam. They constructed
an island in the IJmeer; a small scale
example of Dubai.
We spent the night in a castle in
Heemskerk, where we had a good diner
and drinks.
6HFRQGO\ ZH YLVLWHG WKH FLW\ RI¿FH RI
Culemborg and talked about their urban
‘waterplan’. Investment costs: 8 million
euro in 10 years. They designed the city
quarter Lanxmeer, with a lot of attention
to water, nature, ecology and good
atmosphere. It was a very nice place.
Druppel 3 - 2006
On the 1st and 2nd of June we have
had a very nice excursion for the course
Urban Water Management.
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Haarlem and talked about their integrated
urban ‘waterplan’. They have a progressive
policy in Haarlem towards ground water
management. It was interesting to talk
about their experiences. We also visited
two building sites.
13
Excursion Urban Watermanagement
them, they were still in the building
preparation phase.
For our last visit we headed back to Delft.
We visited the municipality and also met
the waterboard there. They told us about
their waterplan and we visited the city.
They are going to disconnect the city
canals from the Schie. Total costs are 12
million euro. A lot of attention is given to
the communication with the citizens.
Druppel 3 - 2006
After that we visited a Vinex location
in Voorschoten, Krimwijk II, and we
had an excellent lunch there. They are
constructing a city quarter of 23 ha, with
660 houses, in the peat. When we visited
14
We concluded these two days in
restaurant The Casserole in Delft and all
went to bed early I guess. It had been
two very interesting days.
Fourth years project in the Phillippines
Fourth years project in the Phillippines
Joost van den Berg, Matthijs Lemans,
Paul Roeleveld and I did a 2 month
master project in Angeles City, in the
Philippines. The project was about
solving the water problems in Angeles
City. I will not describe our project much
further as we discovered there are only
a few problems in the area. In a way
this was sadly for us, but off course this
is good for them. We have worked on
river modeling, groundwater modeling
and sanitary systems. For this particular
piece in the Druppel, I think it is more
interesting to write about the Philippines
and our experience of working in this
country.
The Philippines is a third world country.
About 40% of the citizens in Angeles City
live below the poverty line. We saw many
people live in self made houses. These
houses were no bigger than 20 square
PHWHUVDQGKRXVHVDERXWSHRSOHRQ
average. The Philippines has a tropical
climate, meaning an average temperature
of 32 degrees and a humidity of 60-80%.
During our stay it was the dry season,
so luckily we did not experience too
many monsoon rains. In the past, the
Philippines was colonized by the Spanish
and Americans. The Filipino people value
their names a lot, so there are a lot of
different names, ranging from Spanish
names to Chinese to American names.
Sometimes these names can be really
funny, most funny of all was Fuk Jou
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called “Joe” or “Hey Joe!”.
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Week”. By coincidence, in our region they
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this week. We just had to see it. The
people do not get to see the part where
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persons hands and feet. So actually,
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DQWLFLSDWHGZHRQO\JRWWRVHHWKH¿QDO
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was quite impressive to see them nailed
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burning sun, with thousands of people
watching them, taking pictures, praying
for them and eating ice cream. Ice cream
vans are all over the Philippines. If you
didn’t see one, you could hear one.
Druppel 3 - 2006
Jair Smits
Fourth years project in the Phillippines
Druppel 3 - 2006
We worked most of the time at the
University of the Philippines in Quezon
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with the technical staff, consisting of
at least 3 people, and the secretary of
the department. During our stay, the
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checked whether the TV was working
every day. In the beginning we had the
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SURIHVVRU DVNHG XV WR VWRS EHIRUH SP
because else the university had to pay
the technical staff extra for overwork,
since they are also in charge of closing
the place.
Transportation was just crazy. The horns
went off non stop, the cars were changing
lanes all the time, there is a near crash
16
event at least once every 3 or 4 minutes
and one of our taxi drivers actually hit
a dog that crossed the street and was
ODXJKLQJ LV DVV RII IRU GRLQJ LW WKH GRJ
was killed).
There are so called Jeepneys all over
the place. These are jeeps that the
Americans left behind, which the people
transformed into some Jamaican looking
YHKLFOHV0RUHWKDQSHRSOHFRXOG¿WLQ
A ride costs up to 10 euro cents.
In our weekends we went out exploring
the Philippines and in the evenings of the
week days we sometimes used to go out,
buy some DVD’s, buy some DVD’s and
meet some Filipino people and buy some
DVD’s.
Internship in Tanzania
Internship in Tanzania
This is a short message from Dares
Salam, Tanzania.
They write the measurements every day
at nine o’clock.
Tanzania is a great country, everyone is
very friendly. The last two weeks actually
were one big jeep safari in a big Land
Rover. You just can’t drive with any other
car on the “roads” of Tanzania.
We’ve been in Dares Salaam for three
days now. We visited a workshop of
the Sokoine University there. Yesterday
we were at the campus of the Dares
University to collect some knowledge
there.
So far I’ve done the following things: I’ve
tried to learn all new names, I’ve tried
to learn Swahili and I’ve fought the rain
gauges and the dust. We have also made
some astonishing walks to collect water
samples and to place new rain gauges.
7KH 0DNDQ\D FDWFKPHQW LV DOPRVW ¿OOHG
with these things. So I’ve also started to
read the measurements of the stations
and collect the data.
One rain gauge usually costs us around
an hour. This is because we need to
get there and collect the data from the
farmers.
Today Marloes went away again. So I’m
alone now, let’s see if I can safely head
back to Makanya tomorrow.
I hope everthing is readable. This was the
supershort story. I fear I need to organise
a slideshow in Delft some day.
This was it, the boy of the internet café
wants to close. By the way, thanks for all
the emails. See you in around 2 weeks.
Regards,
Ben
Druppel 3 - 2006
Benjamin Fischer
17
Master thesis Erik Liefting
Master thesis Erik Liefting
Erik Liefting
Within the framework of the project
‘Interactions in wastewater systems II’
an extensive monitoring campaign is
being set up in the wastewater system
of Eindhoven.
Druppel 3 - 2006
The aim of the measuring program is to
get insight in the water quality processes
in the system. A future goal is to make
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possible.
In total more than 60 sensors will be used
in the Eindhoven wastewater system,
most of which are water quality sensors
and others are water quantity sensors.
Parameters that will be measured
are turbidity, temperature, chemical
R[\JHQ GHPDQG &2' DPPRQLXP DQG
conductivity.
The combination of the large size of
the wastewater system, the amount of
parameters and sensors and the high
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makes it an ambitious project. It will
probably yield millions of data items. The
next challenge is to process those data.
Problems in acquiring data from sewer
systems are many. Often the quality of
the collected data is bad due to failing
sensors or failing data storage. Also
human faults may be a cause of faulty
data.
To be able to handle the concept of data
quality better, we make a distinction
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FRPSOHWHQHVV DFWXDOLW\ DQG YHUL¿DELOLW\
of the data.
18
1. The reliability of the data is their
physical soundness. The reliability can
be affected by non-physical information,
artefacts.
2. The accuracy of the data depends
on the accuracy of the measuring
instruments. However, it is useless to
improve the accuracy when the data are
not reliable.
3. A dataset has to be complete; missing
data decrease the quality level.
4. The data are called actual if no changes
of the conditions since the measuring
period have made them obsolete.
7KH YHUL¿DELOLW\ RI WKH GDWD GHSHQGV
on extra information, for example
information from logbooks and data from
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of) sensors.
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of possible different failing mechanisms,
ranging from installation faults to fouling,
physical breakdown or disordered data
storage.
For my graduation I am checking data
quality on the basis of the abovementioned criteria; in other words, I am
validating data.
Being halfway through my thesis work, I
have developed some tools to research the
data quality, especially their reliability.
I mainly use statistical methods, but
also physical information and models:
ordinary linear regression models and the
more powerful neural networks.
Master thesis Erik Liefting
The next step is to integrate these tools
into one computer program that can
execute all tests on the datasets. With
this program it will be possible to identify
small as well as large data sections with
bad quality. Even single measurements
FDQEH¿OWHUHGRXW
The datasets will be examined separately
as well as combined with other sensor
data; the models are used to identify
a possible correlation between them.
Incidental deviations from that correlation
may indicate artefacts in one ore more
datasets.
All data will be labelled as probably good,
doubtful or probably faulty. The original
datasets will be preserved, but when you
know that the quality of some sections
is probably bad, it is possible to make
new datasets where faulty data are
substituted by interpolated good quality
data. Such datasets can be used to model
the processes in the system better.
Druppel 3 - 2006
The amount of data coming from this
project requires automation of the tests,
so I have written them in Matlab-scripts.
19
Green Roofs
Green Roofs
Sigrid Scherrenberg
This article was written as an assignment for the course Urban Watermanagement and selected as one of the best articles handed in to the teacher.
Druppel 3 - 2006
20
Introduction
This essay about green roofs is not
about roofs which are painted green. It
is about roofs which have a soil layer with
vegetation as a roof, see also Figure 1.
The vegetation has the capacity to reduce
stormwater runoff volumes, to reduce
SHDN ÀRZV DQG WR FRRO EXLOGLQJV GXULQJ
VXPPHUPRQWKV(PLOVVRQDQG5ROI
Köhler et al., 2002). A distinction can be
made between extensive and intensive
JUHHQURRIV0HQWHQVHWDO
Extensive green roofs have a very thin
soil layer which can be down to a few
FHQWLPHWUHV %HQJWVVRQ HW DO WKH VORSH DQJOH RI WKH URRI FDQ EH ƒ
0HQWHQV HW DO 7KHVH URRIV
require almost no maintenance. The
soil can dry out easily, as a result of the
thin layer, when there are long periods
without precipitation. Because of this
special plants, like Sedum album and
Sedum acre, that can survive long dry
SHULRGV DUH XVHG (PLOVVRQ DQG 5ROI
,QWHQVLYHJUHHQURRIVKDYHDWKLFN
soil layer, this layer can be more than
FHQWLPHWUHV %HQJWVVRQ WKH VORSH
RIWKHURRILVOHVVWKDQƒ0HQWHQVHW
DO'XHWRWKLVWKLFNOD\HUWKHURRI
can look like an ordinary garden, even
trees can grow on it. Intensive green
roofs need more maintenance and need
a special roof construction because of the
KHDY\ORDGV(PLOVVRQDQG5ROI
Construction
Building a green roof is not putting some
ground on the roof en letting plants grow
on it. A green roof is an extension of the
H[LVWLQJ URRI )LJXUH PDGH RI D KLJK
TXDOLW\ ZDWHU SURR¿QJ D URRW UHSHOOHQW
V\VWHPDGUDLQDJHV\VWHPD¿OWHUFORWK
a light weight growing medium and plants
*UHHQ5RRIV
Figure: Construction of a green roof
*UHHQ5RRIV
The light weighted growing medium,
or substrate, mainly contains inorganic
material with a high water-holding capacity
and a low density, such as lava, pumice or
H[SDQGHGFOD\(PLOVVRQDQG5ROI
Green roofs can be established on-site or
by bringing prefabricated vegetation to
WKHURRI(PLOOVRQDQG5ROI:KHQ
a green roof is established on-site the
substrate needs to be good and the roof
needs to be covered with plants rapidly
to prevent erosion during rain events
(PLOVVRQDQG5ROI
Green Roofs
Figure: Relationship between the annual
runoff and the annual rainfall for various
URRIV0HQWHQVHWDO
%HQJWVVRQ HW DO IRXQG WKDW WKH
annual runoff from a 3 cm sedum-moss
green roof in Southern Sweden was about
half of the precipitation. Mentens et al.
IRXQGDUHODWLRQVKLSEHWZHHQWKH
annual runoff and the annual rainfall for
YDULRXVURRIV)LJXUH,WLVFOHDUIURP
WKLV ¿JXUH WKDW WKH DQQXDO UXQRII IURP
green roofs is lower compared to the
runoff of a traditional roof. The rainfall
relationship is quadratic for green roofs,
this is due to higher annual precipitations
interfere with a higher amount of extreme
events, for which retentions are lower
0HQWHQVHWDO
Druppel 3 - 2006
Effect on stormwater runoff
Green roofs have the potential of retaining
and delaying rain water during storms
0HQWHQV HW DO $ ODUJH SDUW RI
the rain water gets soaked up in the soil,
a part is used by the plants and a part
evaporates. When the soil on a green roof
gets saturated the excess water will drain
RII *UHHQ URRI (YHQ ZKHQ WKH UXQRII
of these roofs is considerable it may be
delayed relative to the intensive rain and
to the runoff from other surfaces so that
smaller stormwater pipes can be used
compared to an area where no green
URRIVDUH%HQJWVVRQHWDORUWKH
number CSO events can be decreased
9LOODUUHDOHWDO.|KOHUHWDO
Brendtsson et al., 2006).
The maximum stormwater reduction
takes place when the soil is near wilting
point and it starts raining. The soil will
VWRUHZDWHUXQWLOLWUHDFKHV¿HOGFDSDFLW\
The available storage of an extensive roof
FDQ EH DURXQG PP %HQJWVVRQ HW DO
9LOODUUHDO DQG %HQJWVVRQ found that the retention depended for a
great extent on rainfall intensity and the
slope of the green roof. For horizontal
green roofs, under exceptional dry initial
FRQGLWLRQV GXULQJ VXPPHUWLPH XS
WR PP RI UDLQ FRXOG EH VWRUHG WKH
maximum retention of a sloped roof is
10mm. During winter and spring the roof
always contains moist hence the green
roofs are more effective in summertime
WKDQLQZLQWHUWLPH9LOODUUHDOHWDO
When the soil is saturated by stormwater
and another storm follows, no stormwater
reduction will take place, but there will be
a delay because the required time for rain
to travel horizontal and vertical through
the soil will take longer than the time
UHTXLUHGIRUWKHUDLQWRÀRZRIDKDUGURRI
%HQJWVVRQHWDO
Effect on the stormwater quality
Green roofs ensure better surface water
quality as it reduces the pollution caused
by rainwater runoff or by combined sewer
RYHUÀRZV .|KOHU HW DO *UHHQ
roofs also contribute to the reduction of
pollution of roof runoff by absorbing the
pollutants. The runoff quality of green
roofs is expected to be depended of
the thickness of the soil layer, the soil
composition, the type of drainage, the
age of the roof and the type of plants
%HUQGWVVRQHWDO
21
Green Roofs
Care should be taken because green
roofs can also contribute to the pollution
when pollutants are released, for example
when the pH changes heavy metals can
EH UHOHDVHG %HUQGWVVRQ HW DO Another interesting thing is that intensive
green roofs are often fertilized when
they are built and in springtime. Fertilizer
consist of nitrogen and phosphorous
compounds which can also be released
during a storm event.
Druppel 3 - 2006
Figure: Retention of the pollution in
SHUFHQWDJH RI WKH LQSXW .|KOHU HW DO
2002)
,Q.|KOHUHWDO)LJXUHLVVKRZQ
which gives the retention of heavy metals
and nutrients by green roofs. In Sweden
research is done at several locations by
%HUQGWVVRQ HW DO ZKLFK VKRZHG
that extensive roofs did not contribute to
rain water treatment.
Conclusion
Green roofs have the potential of retaining
and delaying rain water during storm
events. Little research has been done
XQWLO QRZ WR LQYHVWLJDWH WKH LQÀXHQFH RI
green roofs on the runoff quality. The
research which has been done does not
all agree with each other.
22
Literature
Bengtsson, L., Grahn, L., Olsson, J.,
+\GURORJLFDO IXQFWLRQ RI D WKLQ
extensive green roof in southern Sweden,
1RUGLF+\GURORJ\9RO1RSS
268
Berndtsson, J.C., Emilsson, T., Bengtsson,
/ 7KH LQÀXHQFH RI H[WHQVLYH
vegetated roofs un runoff water quality,
Science of the Total Environment, Vol.
SS
(PLOVVRQ 7 DQG 5ROI . Comparison of establishment methods for
extensive green roofs in southern Sweden,
Urban Forestry & Urban Greening, Vol. 3,
pp. 103-111
Köhler M., Schmidt, M., Grimme, F.W.,
Laar, M., de Assunção Paiva, V.L., Tavares,
6 *UHHQ URRIV LQ WHPSHUDWH
climates and in the hot-humid tropicsfar beyond the aesthetics, Environmental
Management and Health, Vol. 13, No. 4,
pp. 382-391
Mentens, J., Raes, D. and Hermy, M.,
*UHHQURRIVDVDWRROIRUVROYLQJ
the rainwater runoff problem in the
urbanized 21st century?, Landscape and
Urban Planning, Article in Press, accepted
)HEUXDU\
Villarreal, E.L. and Bengtsson, L.,
5HVSRQVH RI D 6HGXP JUHHQ
roof to individual rain events, Ecological
(QJLQHHULQJ9ROSS
Villarreal, E.L. Semadeni-Davies, A.
DQG %HQJWVVRQ / ,QQHU FLW\
stormwater control using a combination
of best management practices, Ecological
Engineering, Vol. 22, pp. 279-298
Websites
Green Roof: www.greengroof.se
Green Roofs: www.greenroofs.net
Water for Benin
Water for Benin
Dr. P. Bol
Figure: A girl in Benin
Benin is an African country about four
times the size of the Netherlands. Nigeria
and Ghana are well known neighbouring
FRXQWULHV 0$3 ,WV RI¿FLDO ODQJXDJH LV
French. The country has known a period
of communism and was for some time
even a free haven for political extremists.
Those times are long gone and at the
moment Benin is a democracy and has a
rather stable government. It is however
poor, with a yearly income of 1100
dollar per capita and with a third of its
population living below the poverty line.
As in most developing countries, the
availability of clean water is essential for
health improvement but this commodity
is not within reach of everyone. Urban
6FDUFLW\RIHQHUJ\ZRRGNHURVHQHDQG
lack of education and information prevent
proper water treatment and the result is
water-related disease. Particularly gastroLQWHVWLQDO GLVRUGHUV RIWHQ GLDUUKRHDO
diseases) are frequent and also a
prominent cause of death, especially in
FKLOGUHQ XQGHU ¿YH $PRQJ WKHVH DUH
typhoid, bacillary dysentery, amoebic
dysentery, bilharzias, dracontiasis and
hepatitis A.
Druppel 3 - 2006
areas are often served by a water
distribution network organized by the
State Water Company, but most rural
areas are not. Women and girls have to
walk far to fetch water from rivers, pools
and ponds and sometimes from wells.
Invariably the quality of the water is low,
and sometimes it is heavily polluted,
chemically and microbiologically.
Figure: The well works!
The aim of the Dutch-Beninese
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D VXI¿FLHQW DPRXQW RI FOHDQ ZDWHU IRU
villages that are unlikely to be connected
to the main water supply in the foreseeable
future.
23
Water for Benin
At the moment the foundation is busy
setting up wells in 10 villages in the
South-West of Benin, where slow sand
¿OWUDWLRQ V\VWHPV WUHDW DERXW WLOO m3 of pumped up water a day. This is
VXI¿FLHQWGULQNLQJDQGFRRNLQJZDWHUIRU
the communities. At a later stage Le Pont
would like to realize 7 more wells in the
South-East of Benin.
Druppel 3 - 2006
Normally there is a gap between plans
and the situation after realization, and
this is also the case with our projects.
'RULV YDQ +DOHP KDV VSHQW WKUHH
months in Benin at the beginning of this
year. She encountered a lot of problems,
but failures provide a chance to learn and
Le Pont is doing its best to improve the
future works.
Figure: Doris van Halem in Benin
Unique
(QJLQHHUV DQG DOVR GRFWRUV DUH TXLWH
often focused on technical solutions.
But the problems they want to solve
are part of the intrinsic tissue of society.
This implies that sometimes the most
wonderful technical devices will not
work and that very simple non-technical
interventions may work wonders.
24
This is also the case when one changes
the way that water is supplied to people
who for centuries have collected their
water from pools and shallow surfaces.
/HW¶VORRNDWWKHSRVVLEOHGLI¿FXOWLHV
Figure: Putawakou
&OHDQ ZDWHU FRVWV VRPH PRQH\
Though the price is kept low, surface
water is free, although it is at a large
walking distance.
2. Can the population appreciate the
QRQWDVWHRIWDSSHGZDWHU"2XUJUHDW
grandmothers often kept taking water
IURP FDQDOV DQG ULYHUV DIWHU WKH 'HOIW
engineers had supplied their towns with
water networks in the second half of the
19th century. At least the water of one
¿OWHURI/H3RQWLQ%HQLQLVQRWDFFHSWHG
because of its cement taste.
3. Are the people able to understand the
¿OWUDWLRQSURFHVVDQGFDQWKH\KDQGOHWKH
pump and the tap properly? There are
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V\VWHPµFOHDQLQJ¶DQGWKDWHYHQVLPSOH
technical devices are handled wrongly.
Also, ignorance and lack of insight can
cause spillage.
4. Can people grasp the ultimate goal of
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ODERXU PRQH\" 7KDW JRDO LV RI FRXUVH
public and individual health.
Water for Benin
Figure: Women in Benin
Le Pont has taken up an education and
information program to introduce the
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VDIHJXDUG WKH ¿OWUDWLRQ DQG GLVWULEXWLRQ
every water point will have a water
vendor who charges the water per jerry
can taken. But since the price of the
water is kept very low, she cannot make
a living from this.
Therefore the proposal is that she will have
a small vending stall at the water point.
Everyday commodities such as matches,
batteries, snacks, cool drinks and the like
can be obtained there. Most villages don’t
have a shop and the inhabitants have to
travel far to a market town to get their
supplies. The stalls are therefore serving
a need, apart from providing the vendor
with a reasonable income.
This concept reminds one of the so-called
‘komenijswinkels’ in the 19th century
Netherlands. Here, apart from drugstore
and ‘colonial’ articles, one could buy
clean drinking water by the bucket, hot
FRDOVIRUVWDUWLQJWKHVWRYHRU¿UHSODFH
DQGLFHIRUWKHVLFN
Call for support
The Le Pont foundation does not
pretend to have the ultimate knowledge
and insight for solving Benin’s water
problems. If there are any readers who
have alternative views on technological
and organizational aspects, and who
would like to share these with us, we will
be thankful to learn from them. In our
department of Water Management there
are three people who can be contacted:
Dr. ir. Bas Heijman: bas.heijman@kiwa.nl
Doris van Dalem:
D.vanHalem@student.tudelft.nl
Dr. Pieter Bol: pbol@xs4all.nl
Chairman of Le Pont:
Ing. Kees Berkman: info@lepont.nl
ZZZOHSRQWQOWHO
Dr. Pieter Bol is medical epidemiologist
and teaches ‘Public hygiene and
HSLGHPLRORJ\¶&7+HLVDGYLVHURI
the foundation Le Pont.
Druppel 3 - 2006
But even in Holland, after one and half
a century of sanitation, only a small
minority of the population understands
the enormous importance of safe drinking
ZDWHU,KRSHDOOUHDGHUVRIµ'UXSSHO¶DUH
among it!).
Aid for Suriname
7KHÀRRGVZHUHWKHZRUVWLQPHPRU\
Action Committee WiSST
Druppel 3 - 2006
Several parts of the interior of Suriname
were declared disaster areas after being
KLWE\PDVVLYHÀRRGLQJLQWKHEHJLQQLQJ
RI0D\7RUUHQWLDOUDLQVKDYHÀRRGHGWKH
entire south and parts of the central
Amazonian Lowlands of Suriname. Up
WR WKDWFKHGKXW YLOODJHV KDYH EHHQ
submerged under as much as two metres
of muddy water and some are so badly
ÀRRGHG WKDW RQO\ WKH KXW URRIV FDQ EH
seen from the air. The affected districts
include Sipaliwini and Brokopondo, where
most of the inhabitants are descendants
of West African slaves known as Maroons.
7KHVH YLOODJHUV VWDUWHG WR ÀHH WR KLJKHU
grounds when the rains started at the
EHJLQQLQJ RI 0D\ 6RPH SHRSOH
have been directly affected.
In the disaster area the most urgent food,
water and shelter needs have met. While
distribution of food packages is improving,
water and sanitation currently remain
the major concerns. Chlorine tablets
are distributed throughout the area,
but improving access to clean drinking
water remains a major challenge. Several
FDVHVRIGLDUUKRHDKDYHEHHQFRQ¿UPHG
An outbreak of malaria has also been
detected. The lack of proper sanitation
systems and clean drinking water
threatens the health of the population in
WKH DUHD 7KH ÀRRGV ZHUH WKH ZRUVW LQ
the memory of the Surinamese people.
Especially for the ones living on the small
islands in Suriname’s Eastern Rivers,
there was literally no place to go.
Responding to the effects of the
PDVVLYH ÀRRGV WKDW KDYH ODVKHG WKH
QDWLRQ RI 6XULQDPH :,667 :HUNJURHS
26
Inzamelingsactie voor Suriname door
Studenten TUDelft- Action Committee
for Surinam Aid ) has expressed their
concern and solidarity. The action
committee contains TUDelft students
from different educational background
and is established to provide help.
Providing help is done in 2 stages. The
¿UVW VWDJH LV UDLVLQJ PRQH\ IRU ¿UVW DLG
7KLV LV GRQH E\ RUJDQL]LQJ D %HQH¿W
party, collecting around Delft and writing
donation letters to Civil-Engineering
corporations. Secondly, projectgroups
will be formed with the help of prof.
H.H.G.Savenije of Hydrology. prof.
T.Olsthoorn from geohydrology and Prof
J.C.Van Dijk from drinkwater technology.
These project groups will be working
RQ D VWXG\ RI WKH SRVVLELOLWLHV RI ÀRRG
management in the disaster area.
3RVVLELOLWLHV RI ÀRRG FRQWURO DV ZHOO
as safe havens, forecasting, warning
and evacuation will also be taken into
account. Students who are interested
in participating in the project part can
contact Prof.Savenije.
Weather forecasts predict more torrential
rains in the affected areas. This is not
unusual for this period of the year, since
the long wet season in Suriname runs
until the end of July, but it certainly will
have some effects on the water levels.
One night of rainfall could cause a river
to rise again and recovery operations will
have to start all over again.
Donations are still welcome at giro
8978720 ovv WISST. The money will be
doubled by Gemeente Delft.
Indien onbestelbaar retourneren naar:
Dispuut watermanagement - Faculteit Civiele Techniek en Geowetenschappen - TU Delft
Stevinweg 1, kamer 4.74
2628CN Delft