Hydraulics of vegetated flows: estimating riparian plant drag with a view on laser scanning applications

Johanna Jalonen

Hydraulics of vegetated flows: estimating riparian plant drag with a view on laser scanning applications

Julkaisun otsikon käännös: Kasvipeitteisten uomien hydrauliikka näkökulmana virtausvastuksen määrittäminen laserkeilauksen avulla

Johanna Jalonen

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Jokivarsien kasvillisuudella on merkittävä rooli tulvanhallinnassa, eroosiosuojana sekä kiintoaineen ja ravinteiden pidättäjänä. Vedenpinnankorkeuksien, virtausnopeuksien ja aineiden kulkeutumisen arvioimisen luotettavuuden parantamiseksi tarvitaan malleja, jotka käyttävät parametreina kasvien fysikaalisia ominaisuuksia ja ottavat huomioon kasvien muodonmuutoksen virtaustilanteessa (virtaviivaistuminen ja taipuminen). Puiden oksilla tehdyt kourukokeet ovat kuitenkin olleet vaikeasti skaalattavia luonnonpuille ja -pensaille. Modernit kaukokartoitusmenetelmät, kuten maalaserkeilaus (TLS), puolestaan mahdollistavat erittäin tarkan 3D-paikkatiedon keräämisen kasvillisuudesta ja sen ominaisuuksista maastossa. Työn päämääränä oli kasvipeitteisten uomien virtausmallintamisen kehittäminen: 1) määrittämällä päätekijät, jotka vaikuttavat kasvillisuuden aiheuttamaan vastusvoimaan erikokoisilla ja erilaisilla tiheyksillä kasvavalle lehdelliselle, puuvartiselle kasvillisuudelle ja 2) selvittämällä maalaserkeilauksen luotettavuus ruoho- ja puuvartisen kasvillisuuden sekä tulvatasanteen maanpinnan kartoittamiseksi eri vuodenaikoina. Tätä tarkoitusta varten kasvillisuuden virtausvastusvoimia mitattiin laboratoriossa virtauskourussa ja hinausaltaassa. Kourussa kasvitiheyksiä vaihdeltiin sekä muuttamalla yksittäisten kasvien pinta-alaa että kasvien välisiä etäisyyksiä. Hinausaltaassa tutkittiin neljän puulajin vastusvoimia ja muodonmuutoksia virtauksessa 1-3.5 m korkeilla yksilöillä. Maalaserkeilauksia tehtiin sekä hinausallaskokeiden yhteydessä että maastossa tulvatasannealueella. Virtausvastuksen mallinnuksessa tulisi käyttää kaavaa, jossa käytetään kokonaispinta-alaa lehdellisille puille sekä varsipinta-alaa lehdettömille puille. Kaavoissa usein käytetty kasvien projektiopinta-ala ei ole riittävä parametri, sillä lehdet projektiopinta-alan takana aiheuttivat virtausvastusta. Muodonmuutoksen vaikutus virtausvastukseen voitiin kuvata samalla parametriarvolla erikokoisille puille. Kasvillisuuden ominaisuuksien kartoittamiseksi maastossa kehitettiin menetelmä, jolla saadaan laserkeilausaineistosta virtausmallinnuksessa tarvittavat kasviparametrit eri tulvakorkeuksille ja - tarkasteluresoluutioille. Tulvatasanteen taso tulisi mitata keväällä ennen kasvipeitteen muodostumista, sillä erityisesti tiheä ruohomainen kasvillisuus estää lasersäteen pääsyn maahan asti. Maanpinnan tason määritykseen vaikuttavat mm. lasersäteen tulokulma, mittaustiheys sekä kasvillisuus ja sen tyyppi ja tiheys. Väitöskirjan tulokset kasvillisuuden virtausvastuksen määrittämiseksi sekä lähtöaineiston keräämiseksi maastosta toimivat apuna joki- ja vesiympäristön seurannassa ja mallintamisessa.

Julkaisun otsikon käännös	Kasvipeitteisten uomien hydrauliikka näkökulmana virtausvastuksen määrittäminen laserkeilauksen avulla
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Koivusalo, Harri, Vastuuprofessori Järvelä, Juha, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-6384-3
Sähköinen ISBN	978-952-60-6385-0
Tila	Julkaistu - 2015
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

kasvillisuus
virtausvastus
mallinnus
hydrauliikka
maalaserkeilaus
kartoitus

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-6385-0Lisenssi: Määrittelemätön

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@phdthesis{eac60b1182e04aa8851f2f3305a5930a,

title = "Hydraulics of vegetated flows: estimating riparian plant drag with a view on laser scanning applications",

abstract = "In modelling vegetated flows and the associated processes, the flow resistance of riparian vegetation growing along riverbanks and floodplains has received substantial attention. This has led to the development of new resistance or drag force models and the concomitant proposal of several alternative parameters for the resistance estimation. However, the reliability of these models, the effect of reconfiguration (i.e. streamlining and bending of the specimens), and the suitability of different plant parameterizations for woody vegetation of different scales and vegetation densities have remained unclear. Moreover, retrieval of the vegetation properties is laborious with conventional methods. For data retrieval, terrestrial laser scanning (TLS) provides an advanced method which enables high-resolution surveying of floodplain topography and vegetation properties. The aim of this dissertation was 1) to determine the main vegetation properties impacting the drag exerted by woody foliated vegetation of different scales and of varying horizontal and vertical densities, and 2) to assess the reliability of TLS as a method for obtaining herbaceous and woody vegetation properties and floodplain ground level for different seasons. For these purposes, drag force measurements were conducted in a flume in arrays and in a towing tank for natural trees of different sizes. In the flume, the plant areas of the individual specimens and the spacing of the vegetation in an array were both altered. In a towing tank, four species of 0.9-3.4 m in height were experimented together with detailed characterization of tree properties. TLS campaigns were conducted in connection with the towing tank experiments and in a field floodplain site. The stem, leaf, and total areas proved to be reliable vegetation properties for the drag estimation despite the variability in tree height. The commonly applied frontal projected area is not an adequate parameter, as the leaves behind the frontal area still exert drag. The parameterization of the reconfiguration appeared to be independent of the tree size. Consequently, a drag force formula was derived for foliated trees with the total plant area and for the defoliated ones with the stem area as a characteristic reference area. For obtaining plant properties in the field, a new concept was proposed for reach scale analyses based on upscaling of the relationships between TLS data and manually measured plant areas derived for small subareas. Overall, these results of the physically-based modelling of drag forces with the TLS-based plant characterization provide useful knowledge for hydro-environmental modelling purposes.",

keywords = "vegetation, flow resistance, modelling, hydraulics, terrestrial laser scanning, remote sensing, kasvillisuus, virtausvastus, mallinnus, hydrauliikka, maalaserkeilaus, kartoitus, vegetation, flow resistance, modelling, hydraulics, terrestrial laser scanning, remote sensing",

author = "Johanna Jalonen",

year = "2015",

language = "English",

isbn = "978-952-60-6384-3",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "137",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Hydraulics of vegetated flows: estimating riparian plant drag with a view on laser scanning applications

AU - Jalonen, Johanna

PY - 2015

Y1 - 2015

N2 - In modelling vegetated flows and the associated processes, the flow resistance of riparian vegetation growing along riverbanks and floodplains has received substantial attention. This has led to the development of new resistance or drag force models and the concomitant proposal of several alternative parameters for the resistance estimation. However, the reliability of these models, the effect of reconfiguration (i.e. streamlining and bending of the specimens), and the suitability of different plant parameterizations for woody vegetation of different scales and vegetation densities have remained unclear. Moreover, retrieval of the vegetation properties is laborious with conventional methods. For data retrieval, terrestrial laser scanning (TLS) provides an advanced method which enables high-resolution surveying of floodplain topography and vegetation properties. The aim of this dissertation was 1) to determine the main vegetation properties impacting the drag exerted by woody foliated vegetation of different scales and of varying horizontal and vertical densities, and 2) to assess the reliability of TLS as a method for obtaining herbaceous and woody vegetation properties and floodplain ground level for different seasons. For these purposes, drag force measurements were conducted in a flume in arrays and in a towing tank for natural trees of different sizes. In the flume, the plant areas of the individual specimens and the spacing of the vegetation in an array were both altered. In a towing tank, four species of 0.9-3.4 m in height were experimented together with detailed characterization of tree properties. TLS campaigns were conducted in connection with the towing tank experiments and in a field floodplain site. The stem, leaf, and total areas proved to be reliable vegetation properties for the drag estimation despite the variability in tree height. The commonly applied frontal projected area is not an adequate parameter, as the leaves behind the frontal area still exert drag. The parameterization of the reconfiguration appeared to be independent of the tree size. Consequently, a drag force formula was derived for foliated trees with the total plant area and for the defoliated ones with the stem area as a characteristic reference area. For obtaining plant properties in the field, a new concept was proposed for reach scale analyses based on upscaling of the relationships between TLS data and manually measured plant areas derived for small subareas. Overall, these results of the physically-based modelling of drag forces with the TLS-based plant characterization provide useful knowledge for hydro-environmental modelling purposes.

AB - In modelling vegetated flows and the associated processes, the flow resistance of riparian vegetation growing along riverbanks and floodplains has received substantial attention. This has led to the development of new resistance or drag force models and the concomitant proposal of several alternative parameters for the resistance estimation. However, the reliability of these models, the effect of reconfiguration (i.e. streamlining and bending of the specimens), and the suitability of different plant parameterizations for woody vegetation of different scales and vegetation densities have remained unclear. Moreover, retrieval of the vegetation properties is laborious with conventional methods. For data retrieval, terrestrial laser scanning (TLS) provides an advanced method which enables high-resolution surveying of floodplain topography and vegetation properties. The aim of this dissertation was 1) to determine the main vegetation properties impacting the drag exerted by woody foliated vegetation of different scales and of varying horizontal and vertical densities, and 2) to assess the reliability of TLS as a method for obtaining herbaceous and woody vegetation properties and floodplain ground level for different seasons. For these purposes, drag force measurements were conducted in a flume in arrays and in a towing tank for natural trees of different sizes. In the flume, the plant areas of the individual specimens and the spacing of the vegetation in an array were both altered. In a towing tank, four species of 0.9-3.4 m in height were experimented together with detailed characterization of tree properties. TLS campaigns were conducted in connection with the towing tank experiments and in a field floodplain site. The stem, leaf, and total areas proved to be reliable vegetation properties for the drag estimation despite the variability in tree height. The commonly applied frontal projected area is not an adequate parameter, as the leaves behind the frontal area still exert drag. The parameterization of the reconfiguration appeared to be independent of the tree size. Consequently, a drag force formula was derived for foliated trees with the total plant area and for the defoliated ones with the stem area as a characteristic reference area. For obtaining plant properties in the field, a new concept was proposed for reach scale analyses based on upscaling of the relationships between TLS data and manually measured plant areas derived for small subareas. Overall, these results of the physically-based modelling of drag forces with the TLS-based plant characterization provide useful knowledge for hydro-environmental modelling purposes.

KW - vegetation

KW - flow resistance

KW - modelling

KW - hydraulics

KW - terrestrial laser scanning

KW - remote sensing

KW - kasvillisuus

KW - virtausvastus

KW - mallinnus

KW - hydrauliikka

KW - maalaserkeilaus

KW - kartoitus

KW - vegetation

KW - flow resistance

KW - modelling

KW - hydraulics

KW - terrestrial laser scanning

KW - remote sensing

M3 - Doctoral Thesis

SN - 978-952-60-6384-3

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Hydraulics of vegetated flows: estimating riparian plant drag with a view on laser scanning applications

Abstrakti

Tutkimusalat

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