UNIVERSITI PUTRA MALAYSIA

EFFECTS OF FOREST HARVESTING OPERATIONS ON SUSPENDED SEDIMENT AND SOLUTE LOADS IN THE SUNGAI WENG EXPERIMENTAL WATERSHEDS, KEDAH, PENINSULAR

MALAYSIA

INTHAVY AKKHARATH.

FH 2005 1

EFFECTS OF FOREST HARVESTING OPERATIONS ON SUSPENDED SEDIMENT AND SOLUTE LOADS IN THE SUNGAI WENG

EXPERIMENTAL WATERSHEDS, KEDAH, PENINSULAR MALAYSIA

BY

INTHAVY AKKHARATH

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Doctor of Philosophy.

August 2005

SPECIAL DEDICATION

TO MY BE LOVED WIFE, SISONGKHAM AND OUR CHILDREN KITTIPHANH, THANTHIVA AKKHARATH AND TO MY PARENTS, MR LEOKHAM AND MRS SOMSY AKKHARATH, WHO LAID MY ACADEMIC CAREER FOUNDATlON AND TO ALL OF THE AKKHARATH FAMILY MEMBERS FOR THEIR CONSTANT MORAL SUPPORT AND INSPIRATIONS. GOD BLESSES THEM ALL!

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirements for the degree of Doctor of Philosophy

EFFECTS OF FOREST HARVESTING OPERATIONS ON SUSPENDED SEDIMENT AND SOLUTE LOADS IN THE SUNGAI WENG

EXPERIMENTAL WATERSHEDS, KEDAH, PENINSULAR MALAYSIA

INTHAVY AKKHARATH

August 2005

Chairman: Associate Professor Lai Food See, PhD

Faculty: Forestry

This study examines the effects of logging operations on sediment and solute yields

in four steep catchments referred to as the Sungai Weng Experimental Watersheds

located in Ulu Muda Forest Reserves Kedah, Peninsular Malaysia. Watershed 1

(W 1) is a control catchment where logging was not allowed throughout the period of

study. Watershed 2 (W2) was logged based on stringent guidelines as recommended

by the Forestry Department hitherto referred to as reduced impact logging (RIL).

Watershed 3 (W3) was logged based on conventional logging (CL) practices.

Watershed 5 (W5) is a bigger watershed, where the experimental basins are nested

within and selected to examine the downstream and cumulative effects of logging

operations including in those areas worked previously.

The general aim of this study was to compare the relative impacts of CL and RIL on

sediment output. In this study, the extent of sediment source areas in W2 and W3 in

the form of roads, skid trails and log landings and their implication on sediment

output was also examined. In W2, the logging roads density was 30 mlha, while the

density of skid trail was 68 mlha and the exposed area was 43 ha, about 5% of total

watershed area. In W3, the logging road density was 47 rnlha and the density of skid

trail was 10lmha; exposed area was 59 ha, about 9% of watershed area.

The most reliable and suitable method was chosen to determine the sediment yield

of the four catchments was estimated using data assembled for the rising and falling

discharge stages. In W 1, suspended sediment concentrations are high during storms

even though under natural forests. The peak concentrations sampled were between

1,278 to 1,896 mgll from 1997 to 2002 respectively. The annual sediment yields

were 160, 199, 148, 97, 79, and 80 t/km2/yr generated fiom 1997 to 2002

respectively.

During logging operations, in W2, the annual sediment yields significantly increased

from 176 to 1,15 1 t/km21yr in year 2000 and 2002 respectively. In W3, the sediment

yields increased dramatically to 2,133; 5,386; 4,501 t/km2/yr over the period of 1998

to 2000 respectively. After logging ceased, sediment yield decreased to 869 and 684

t/km2/yr from 2001 and 2002 respectively. Sediment yield in W5 was much less

even though, the sediment yields fiom the experimental watersheds W3, in particular

was high. Depositions of sediment along the stream channel leading to the gauging

. . . 111

site of W5 and dilution from upstream channels were the main reason for the lower

yield. Therefore, in W5 the sediment yield was contributing 143, 284, 829,458, 178,

and 163 tlkm2/yr, in over the six-year period from 1997 to 2002 respectively.

Stream water quality was measured in each study watershed and the results revealed

that solute loads were much lower than sediment loads. In W1, the annual solute

yields were 12.5, 13.5, 20.1, 14.8, 13.7, and 13.8 tlkm2/yr generated from 1997 to

2002 respectively. During logging operations, in W2, solute yields were 20.3, 13.4,

11.3 t h 2 / y r , for the year 2000, 2001 and 2002, respectively. In W3, solute out put

was 30.8, 27.0 and 20.0 t/lun21yr. However, the annual sediment yields appeared to

have declined to 18.0 and 14.2 tkm2/yr, in the following two years 2001 and 2002,

respectively. In W5, solute out put was contributing 17.5, 16.8, 27.0, 25.4, 23.1 and

17.3 tlkm2/yr, in over the six-year period from 1997 to 2002.

The results of the study suggest that with proper control measures, the effects of

logging on sediment loads in particular, can be substantially reduced. The increase

of sediment yield in W2 to l , l5 1 t/km21yr in 2002 with 80% the study watershed

was logged suggests that RIL exerted significant influence on sediment output. With

respect to pre-logging or control conditions, the analyses suggest that conventional

logging can results in over 40 times the sediment yield during the logging

operations. The positive effects of RIL can be achieved through carehl planning,

scheduling and control of logging operations.

Abstrak tesis yang dikemukakan kepada Senat Univeristi Putra Malaysia sebagai memenuhi keperluan untuk ijazah Doktor Falsafah

KESAN-KESAN OPERAS1 PENUAIAN HUTAN KE ATAS MENDAPAN MAMPAT DAN MUATAN BAHAN KIMIA DI KAWASAN KAJIAN

'TADAHAN AIR SUNGAI WENG, KEDAH, SEMENANJUNG MALAYSIA.

Oleh

INTHAVVY AKKHARATH

Ogos 2005

Pengerusi: Profesor Madya Lai Food See, PhD

Fakulti: Perhutanan

Kajian ini adalah untuk mengenalpasti kesan-kesan operasi pembalakan ke atas

pemendapan mendapan di empat lokasi kawasan kajian tadahan air yang curam yang

terletak di Hutan Simpan Ulu Muda, Kedah, Semenanjung Malaysia. Tadahan air 1

(Wl) adalah sebagai tadahan air kawalan di mana pembalakan tidak dibenarkan

sepanjang tempoh kajian. Tadahan air 2 (W2) adalah kawasan yang telah dibalak

mengikut garispanduan yang ketat yang disyorkan oleh Jabatan Perhutanan iaitu

mengurangkan kesan pembalakan (Reduced Impact Loging). Tadahan air 3 (W3)

adalah kawasan dibalak berdasarkan kepada a m a h pembalakan konvensional

(Conventional logging). Tadahan air 5 (W5) adalah kawasan tadahan air yang besar,

di mana lembah kajian yang dipilih dan diasingkan kepada beberapa bahagian untuk

mengkaji kesan-kesan hiliran dan kumulatif operasi pembalakan termasuk dalam

kawasan yang telah dikerjakan sebelum ini.

Tujuan umum kajian ini adalah untuk membandingkan impak relatif (CL) dan (RIL)

ke atas keluaran mendapan. Dalam kajian ini, perkembangan kawasan-kawasan

sumber mendapan dalam W2 dan W3 dalam bentuk jalan utama, jalan penarik dan

matau balak dan implikasinya keatas keluaran mendapan juga dikaji. Dalam W2,

kepadatan jalan-jalan pembalakan adalah 30m/ha, manakala kepadatan jalan penarik

adalah 68mha dan kawasan lapang terbuka adalah 43 ha, kira-kira 5% daripada

keseluruhan kawasan tadahan. Dalam W3, kepadatan jalan pembalakan adalah

47mlha dan kepadatan jalan penarik adalah 10 1 m/ha, kawasan terdedah adalah 59 ha

kira-kira 9% daripada kawasan tadahan.

Kaedah yang boleh dipercayai dan sesuai dipilih bagi menentukan hasil mendapan

bagi keempat-empat tadahan air seterusnya dianggarkan dengan menggunakan data

gabungan peringkat kenaikan dan kejatunan bahan buangan. Dalam W1, kepekatan

mendapan adalah tinggi semasa ribut walaupun di hutan asli. Sampel yang

mempunyai kepekatan puncak adalah 160, 199,148,97,79 d m 80 t/km21yr didapati

daripada 1997 hingga 2002.

Semasa operasi pembalakan, dalarn W2 hasil mendapan tahunan meningkat dengan

Sangay bererti dari 176 ke 1,15 1 80 t/km2/tahun masing-masing pada tahun 2000

dan 2002. Dalam W3, hasil mendapan tahunan adalah meningkat secara mendadak

vi

ke 2,133; 5,386; 4,501 80 t/km2/tahun iaitu masing-masing dalam jangka masa tahun

1998 dan 2000. Selepas pembalakan, hasil mendapan berkurangan dari 869 ke 684

80 t/km21yr iaitu pada tahun 2001 dan 2002. Hasil mandapan di W5 adalah

berkurangan walaupun hasil mendapan di kawasan kajian tadahan di W3 adalah

tinggi. Pembuangan mendapan di sepanjang laluan air mengakibatkan kawasan

'gauging' di W5 dan pelarutan mendapan dari kawasan tadahan air atas adalah

alasan utama menyebabkan kesan mendapan yang rendah. Walaubagaimanapun, di

W5 hasil mendapan menyumbang sebanyak 143, 284, 829, 458, 178 dan 163 80

t/km21yr dalam jangkamasa 6 tahun daripada tahun 1997 hingga 2002.

Keputusan kualiti air sungai diukur dalam setiap kajian tadahan air menunjukkan

muatan bahan kimia adalah terlalu rendah daripada muatan mendapan. Di W1,

penghasilan bahan kimia tahunan menyumbang kepada12.5, 13.5, 20.1, 14.8, 13.7

dan 13.8 t/km2/tahun daripada tahun 1997 hingga 2002. Di W2, tiga tahun pertama

sebelum operasi pembalakan, keluaran 'solute" adalah 18.6, 13.3, 28.5 t/km2/tahun

untuk tahun 2000, 2001 dan 2002. Di W3, keluaran 'solute' hhdala 30.8, 27.0 dan

20.0 80 t/km2/tahun pada dua tahun berikutnya pada tahun 2001 dan 2002. Di W5,

keluaran 'solute' menyumbang kepada 17.5 16.8, 27.0, 25.4, 23.1 dan 17.3 80

t/km2/tahun dalam tempoh enam tahun iaitu dari 1997 hingga 2002.

Keputusan kajian mengesyorkan bahawa perlunya kawalan yang sempurna

terutamanya bagi mengurangkan kesan mendapan akibat aktiviti pembalakan.

Pertarnbahan hasil mendapan di W2 sehingga 1,151 t/km2/tahun dalarn tahun 2002

vii

dengan meliputi 80% kajian tadahan pembalakan menunjukkan RIL 'exerted'

menyebabkan perbezaan yang bererti ke atas keluaran mendapan. Berdasarkan

kepada keadaan sebelum pembalakan atau kawalan kajian, analisa mencadangkan

pembalakan konvensional akan menghasilkan lebih 40 kali hasil mendapan semasa

operasi pembalakan. Walaubagaimanapun, dalam peringkat yang tertentu, RIL boleh

dicapai melalui perancangan yang berhati-hati, penjadualan dan kawalan operasi

pembalakan.

. . . V l l l

ACKNOWLEDGEMENT

First of all I would like to express my heartfelt gratitude and appreciation to my

supervisor, Assoc. Prof. Dr. Lai Food See for his invaluable help, dedicated efforts,

guidance, suggestions and construction criticisms throughout this study. I am also

very grateful indeed to my supervisory committee members Prof. Lee Chnnong

Kheng and Prof. Dato' Dr. Nik Muharnad Nik Ab Majid for their kind assistance,

painstaking furnished countless invaluable comments and suggestions to improve

this study. I am truly indebted to them. I also appreciate Mdam Choo Chai Syam for

assisting in water chemistry analysis and my gratitude also goes to Mr. Albert Tan

for providing digitized mads.

I would like to express my sincere thanks and appreciation to the Muda Agricultural

Development Authority (MADA) for providing financial support. For these, I would

like to express deep gratitude to all staff of special thanks Ir. Foong Kam Chong,

Head of Engineering Division, Ir. Loh Kim Mon, Head of Planning and design

section and Ir. Geh Yean Lian, Head of Dam management section. My thanks also to

Mr. Zaim bin Abdul Rashid, Mohd Zuki bin Harun and Kharuldin bin Nai, Khairul

Anas and Khairul Anwar bin Said for field work assistance and data collection

during this study. I would like to thank Ir. Low Koon Sing of Drainage and

Irrigation Department (DID) Arnpang, Kuala Lumpur and his staff for their

providing the discharge data and rainfall data for use in this study.

My sincere thanks are also due to various individuals; Mr Khampheuane Kingsada,

Director General of Lao Forestry Department and Mr. Vongxay Norakham, Head of

Forest Inventory and Planning section of Forestry Department in Vinetiane, Laos for

their provided me a study leaf during my M.Sc and Ph.D. progammes. Profound

appreciation and thanks are also extended to, Mr. Zahari Bin Ibrahim, Mr. Ariffin

Abdu, Mr. Bounheaung Ninchaleune and Manichanh Sayavong for their love,

encouragement, support and prayer. I love you all.

I am indebted to my parents, who gave support in my academic pursuit. My heartfelt

thanks are extended to my brothers, sisters, and every member of my family for their

undivided love throughout PhD programme. Lastly, my special and deepest thanks

and love towards my wife, Sisongkharn Chanthavong for her love, sacrifice,

patience, support, and encouragement. My children, Kittiphanh and Thanthiva

Akkharath, in their own ways have continuously provided me with love and

inspiration. They patiently tolerated my preoccupation with my studies and work.

My special love to them.

I certify that an Examination Committee met on 29h August 2005 to conduct the final examination of Inthavy Akkharath on his Doctor of Philosophy thesis entitled "Effects of Forest Harvesting Operations on Suspended Sediment and Solute Loads in the Sungai Weng Experimental Watersheds, Kedah, Peninsular Malaysia" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act I980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

MOHAMED ZAKARIA HUSSIN, PhD Associate Professor Faculty of Forestry Universiti Putra Malaysia (Chairman)

AHMAD AINUDDIN NURUDDIN , PhD Associate Professor Faculty of Forestry Universiti Putra Malaysia (Internal Examiner)

WAN NOR AZMIN SULAIMAN, PhD Associate Professor Faculty of Environmental Studies Universiti Putra Malaysia (Internal Examiner)

SHARIFAH MASTURA SYED ABDULLAH, PhD Professor Faculty of Social Sciences and Humanities Universiti Kebangsaan Malaysia (External Examiner)

Universiti Putra Malaysia

Date: 25 OCT 2005

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfillment of the requirement for the degree of Doctor of Philosophy. The members of the Supervisory Committee are as follows:

LA1 FOOD SEE, PhD Associate Professor Faculty of Forestry Universiti Putra Malaysia (Chairman)

LEE CHNONG KHENG, PhD Professor Faculty of Science Universiti Putra Malaysia (Member)

DATO' NIK MUHAMAD NIK AB MAJID, PhD Professor Faculty of Forestry Universiti Putra Malaysia (Member)

AINI IDERIS, PhD Professor/Dean School of Graduate Studies Universiti Putra Malaysia

Date: 1,7 NOV 2005

xii

DECLARATION

I hereby declare that the thesis is based on my original research work except for quotations and citations, which have been duly acknowledge. I also declare that it has not been previously or concurrently submitted for any other degree at Universiti Putra Malaysia or other institutions.

INTHAVY AKKHARATH

. . . Xll l

TABLE OF CONTENTS

Page

DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS LIST OF TABLES LIST OF FIGURES LIST OF PLATES LIST OF ABBREVIATIONS

CHAPTER

INTRODUCTION General Background Statement of the Problems Objectives of the Study Study Approach Organisation of the Thesis

LITERATURE REVIEW Introduction Forest Logging Systems

Monocyclic Logging Polycyclic Logging

Reduced Impact Logging Pre-logging Planning; Contracts and Conditions Stream Buffer Strips Logging Road Construction Skid Trail Construction Log Landing Construction

Sediment Sources and Transport Past and Present Research on Sediment Yield

in Tropical Catchments Experimental Catchments Suspended Sediment Solutes

Summary

MATERIALS AND METHODS Introduction Location

1X

xviii xxi

xxiv xxv

xiv

Watershed Characteristics Catchment Physiography

Topography Basin Slope Classification Drainage

Climate General Rainfall Pattern

Geology and Lithology Soil Characteristics Forest Type in Study Watersheds Hydrological Characteristics

Rain Gauges Rainfall Data Collection Stream Flow Stations Stream Gauging Automatic Water Samplers

Laboratory Procedure in Suspended Sediment Separation Analyses of Suspended Sediment and Filtrate Separation

Water Chemistry Analysis of Water Chemistry

Treatment of the Study Catchments Road Construction and Drainage Skid Trail Bridge Construction Landing

Past Forestry Operations in W5 Logging Phases in W2 and W3

Statistical Approaches Summary

SEDIMENT SOURCES; ROADS, SKID TRAILS AND LOG LANDING Introduction Characteristics of Roads, skid trials and landing

in W2and W3 Distribution and Location of Roads, Skid trails and Landing

for each Logging Block in W2 and W3 Sediment Sources Comparison with Forestry Guidelines Summary

SEDIMENT TRANSPORT AND YIELD Introduction Catchment hydrology Stream Discharge

Observations of suspended sediment Concentrations Suspended Sediment Load Computation Sediment Production Computation

Base-flow Separation Suspended Sediment Transport during

Period of Observations W1 W2 W3 W5

Summary

VI STREAM WATER CHEMISTRY Introduction Stream water quality

Conductivity Silica Calcium Potassium Magnesium Sodium Iron and Aluminium

Storm variation W1 W2 and W3 Concentration Changes Resulting Logging operations W5 Summary

Solute Yields W1 W2 W3 W5

Summary

VII DISCUSSION Introduction Suspended Load

Pre-logging During Logging Operations Post Logging Comparison with Other Studies

Solute Load Pre-logging During Logging Operations Post Logging

xvi

Comparison with Other Studies Summary

VIII CONCLUSION AND RECOMMENDATION Conclusion Recommendation

Summary

BIBLIOGRAPHY APPENDICES BIODATA OF THE AUTHOR

xvii

LIST OF TABLES

Table

1.1

2.1

2.2

Permanent reserved forestland in peninsular Malaysia

Experimental catchment in Malaysia

Page

3

30

Prescriptions for the supervised and unsupervised commercial logging in Berembun Experimental watershed 3 1

Sediment yields of selected catchments from tropical catchment

Solute loads of selective tropical catchments

Watershed characteristics of the Sg.Weng experimental watersheds

Slope classification of Sg. Weng experimental watersheds

Catchment location and proportion of productive forest in the experiment watershed

Type of rain gauge used in the study watersheds

Type of water-level recorders used in the study watersheds

Type of automatic water samplers used

Laboratory procedure for suspended sediment and filter separation

Logging prescriptions in the conventional logging and reduced impact logging catchments

Logging phases in compartments within study watersheds

Characteristic of roads, skid trails, and landing as determine from Topographic map and observation of watershed studies

W2, Roads, skid trails, and landings as determine from topographic map and observation of study blocks

W3, Roads, skid trails, and landings as determine from topographic map and observation of study blocks

xviii

Comparison of the construction and area exposure of roads and skid trails and landing with other studies

Particulars on logging operation in the study watersheds

Monthly rainfall and runoff data for study watersheds (mm)

Statistics of suspended sediment concentration (mgll)

Summary of maximum suspended sediment concentration distribution is study watersheds

Statistics of suspended sediment concentration (mgll)

W 1, summary of values of rating curves

W2, summary of values of rating curves

W3, summary of values of rating curves

W5, summary of values of rating curves

W 1, summary of suspended sediment load values

5.10 W2, summary of suspended sediment load values

5.1 1 W3, summary of suspended sediment load values

5.12 W5, summary of suspended sediment load values

5.13 W 1, suspended sediment production (Method B)

5.14 W2, suspended sediment production (Method B)

5.15 W3, suspended sediment production (Method B)

5.16 W5, suspended sediment production (Method B)

W 1, summary of stream water chemistry

W2, summary of stream water chemistry

W3, summary of stream water chemistry

W5, summary of stream water chemistry

xix

W1, stream water chemistry for storm of 13-1 1-01

W2, stream water chemistry for storm of 22-10-99 and 23-10-99

W2, stream water chemistry for storm of 15-10-2001

W3, stream water chemistry for storm of 23-05-1999

W5, stream water chemistry for storm of 09-10-99

6.10 W 1, monthly loads of individual element (t/km2)

6.1 1 W1, percentage of individual elemental for monthly loads to total monthly solute out put for respective months

6.12 W2, monthly loads of individual element (t/km2)

6.13 W2, percentage of individual elemental for monthly loads to total monthly solute out put for respective months

6.14 W3, monthly loads of individual element (t/km2)

6.15 W3, percentage of individual elemental for monthly loads to total monthly solute out put for respective months

6.16 W5, monthly loads of individual element (Vkrn2)

6.17 W5, percentage of individual elemental for monthly loads to total monthly solute out put for respective months

6.18 Summary of solute yield estimation for watersheds (Vkrn2/yr)

Level of significance of differences between suspended sediment loads of the catchment using ANOVA (1997-2002)

Sediment loads from selected catchments in tropical forest

Level of significance of differences between ions concentration (C) and monthly solute loads (MSL) of study catchment using ANOVA 245

Solute loads of selected tropical catchment (t/km2/yr)

LIST OF FIGURES

Figure

2.1 Uphill and downhill log extractions

3.1 Location of the study site, Sg. Weng Experimental Watersheds

3.2 Layout of the Sg.Weng Experimental Watersheds

3.3 Mean monthly rainfall between Baling district and study watersheds from 1996 to 2002

3.4 Location of the study watersheds and their surrounding geology

3.5 The legends of geology map

3.6 Soil series map in W1, W2 and W3

3.7 Symington's (1943) altitudinal forest zones and elevation of study catchment in Peninsular Malaysia

3.8 Rain gauge and streamflow stations in the study watersheds

Forest compartments located in the study watershed

W2, Location and distribution of roads, skid trail, and landing on mapping

W3, Location and distribution of roads, skid trail, and landing on mapping

Rainfall and runoff relationship and distribution at W1 and W2 1997-2002

Rainfall and runoff relationship and distribution at W3 and W5 1997-2002

Stage discharge-rating curve at W1 and W2

Stage discharge-rating curve at W3 and W5

Mean monthly rainfall and mean monthly discharge for W 1 and W2 fiom 1997 to 2002

xxi

Page

22

42

44

Mean monthly rainfall and mean monthly discharge for W3 and W5 from 1997 to 2002

W 1, Suspended sediment rating curves (1 997-2002)

W2, Suspended sediment rating curves (1 997-1 999)

W2, Suspended sediment rating curves (2000-2002)

5.10 W3, Suspended sediment rating curves (1 997-2002)

5.1 1 W5, Suspended sediment rating curves (1997-2002)

5.12 Baseflow separation

5.13 W 1, monthly suspended sediment yield

5.14 W2, monthly suspended sediment yield

5.1 5 W3, monthly suspended sediment yield

5.16 W5, monthly suspended sediment yield

5.17 W 1, W2; monthly suspended sediment yield and discharge

5.18 W3, W5; monthly suspended sediment yield and discharge

Overall mean conductivity with standard deviation during baseflow and stormflow in all study watersheds (1997-2002)

Overall mean element concentrations with standard deviation during baseflow and stormflow in W l(1997-2002)

Overall mean element concentrations with standard deviation during baseflow and stormflow in W2 (1 997-2002)

Overall mean element concentrations with standard deviation during baseflow and stormflow in W3 (1 997-2002) 185

Overall mean element concentrations with standard deviation during baseflow and stormflow in W5 (1997-2002)

W 1, Behaviour of individual ion during storm runoff on 13- 1 1-0 1

W2, Behaviour of individual element during storm runoff of 22-10-99 to 23-10-99

xxii

W2, Behaviour of individual element during storm runoff of 15-10-01

W3, Behaviour of individual element during storm runoff of 23-05-99

6.10 W5, Behaviour of individual element during storm runoff of 23-05-99

xxiii