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A GIS-RS COMPATIBLE A GIS-RS COMPATIBLE RAINFALL-SURFACE RAINFALL-SURFACE RUNOFF MODEL FOR RUNOFF MODEL FOR
REGIONAL LEVEL REGIONAL LEVEL PLANNINGPLANNING
A GIS-RS COMPATIBLE A GIS-RS COMPATIBLE RAINFALL-SURFACE RAINFALL-SURFACE RUNOFF MODEL FOR RUNOFF MODEL FOR
REGIONAL LEVEL REGIONAL LEVEL PLANNINGPLANNING
Fig. Schematic diagram of a drainage network
Fig. Flow rates or discharge at points of interest along streams
Q
Q
Q
Q
Q
Q
Q
= Discharge
Development of a physically Development of a physically
based rainfall surface runoff based rainfall surface runoff
model for simulating flood model for simulating flood
hydrographs in user friendly hydrographs in user friendly
interface (GUI)interface (GUI)
Development of a physically Development of a physically
based rainfall surface runoff based rainfall surface runoff
model for simulating flood model for simulating flood
hydrographs in user friendly hydrographs in user friendly
interface (GUI)interface (GUI)
Data obtained by running the model may be used on certain water resources projects.
Bridges, Culverts and Aqueducts
Spillways for small dams
Levees for flood protection
MODEL UTILITY FOR PRACTICAL APPLICATIONS
Predicting erosion potential due to land use change
Site planning for micro hydels
Agriculture
CHIRADEEP ADHIKARICHIRADEEP ADHIKARI
(M.TECH.,APPLIED GEOLOGY, IIT KHARAGPUR)(M.TECH.,APPLIED GEOLOGY, IIT KHARAGPUR)
GIS ANALYSTGIS ANALYSTConsulting Engineering Services (India) Pvt. Ltd.Consulting Engineering Services (India) Pvt. Ltd.
E-MAIL: [email protected]: [email protected]
CHIRADEEP ADHIKARICHIRADEEP ADHIKARI
(M.TECH.,APPLIED GEOLOGY, IIT KHARAGPUR)(M.TECH.,APPLIED GEOLOGY, IIT KHARAGPUR)
GIS ANALYSTGIS ANALYSTConsulting Engineering Services (India) Pvt. Ltd.Consulting Engineering Services (India) Pvt. Ltd.
E-MAIL: [email protected]: [email protected]
STYDY AREA
BANKURA ADMINISTRATIVE MAP WEST BENGAL MAP
STUDY AREA
Location
22 46 00 – 22 51 00 N, 86 42 00 – 86 51 00 E, western parts of Bankura District, West Bengal.
Area
124 sq.km ( approx.)
Physiography
Residual hillocks and mounts and also in some parts upper undulating alluvial plain.
Drainage
Dendritic in nature mainly.
Lithology
Mainly of metasediments e.g.; mica - sillimanite schist, quartzite, hornblende schist, amphibolite
Climate
Sub - tropical climatic zone characterized by hot summer and cool winter.
The monthly average rainfall ranges from 3.88 mm ( January) to 352.41 mm ( July ) with an annual average of 1365.24 mm.More than 80 % of the rain occurs in between June and September and heaviest rain occurs in July generally.
DRAINAGE WITH CONTOURS
DRAINAGE
CONTOUR
BOUNDARY
PART I : REPRESENTATION OF SURFACE GEOMETRY PART I : REPRESENTATION OF SURFACE GEOMETRY
FLOW CHART- METHODOLOGY
PART II : WATERSHED TERRAIN MODELLING
PART III : RUNOFF COMPUTATION FROM WATERSHED
METHODOLOGY – PART I
REPRESENTATION OF SURFACE GEOMETRY
WITHOUT GIS SOFTWARE
WITH GIS SOFTWARE
TOPOSHEET
REPRESENTATION OF SURFACE GEOMETRY
CONTOUR
DRAINAGE
TIN
WITH GIS SOFTWARE
TOPOSHEETCONTOUR
DRAINAGE DRAW TIN
PLOT ON
GRAPH
POINT NO. X Y Z
TRIANGLE NO. V1 V2 V3
OUTPUT DATA FORMAT
WITH GIS SOFTWARE
TIN DATA FILE
DATA CONVERTED TO
WITHOUT GIS SOFTWARE
DATA
DATA STORED AS
REPRESENTATION OF SURFACE GEOMETRY- DATA FORMAT
TRIANGULATED IRREGULAR NETWORK ( TIN )
FLOW CHART- METHODOLOGY
PART I : REPRESENTATION OF SURFACE GEOMETRY
PART II : WATERSHED TERRAIN MODELLINGPART II : WATERSHED TERRAIN MODELLING
PART III : RUNOFF COMPUTATION FROM WATERSHED
METHODOLOGY – PART IIWATERSHED TERRAIN MODELLING
WATERSHED TERRAIN MODELLING
IDENTIFICATION OF WATERSHED FEATURES
(RIDGE, CHANNEL, FLOW BOUNDARY SEGMENTS)
IDENTIFICATION OF CHANNEL NETWORK
IDENTIFICATION OF OVERLAND FLOW CASCADES
LENGTH,WIDTH AND SLOPE OF CASCADE PLANES
I. GLOBAL NUMBERING OF EDGES OF THE TRIANGLES
II. IDENTIFYING EDGE NUMBERS THAT FORM THE SIDES OF THE TRIANGLE
I. PRINCIPAL SLOPE VECTORS OF TRIANGLES
II. DIRECTION OF SLOPE VECTOR RELATIVE TO THE THREE EDGES OF TRIANGLE
III. DIRECTION OF THE SLOPE VECTORS OF CONNECTED TRIANGLES FOR EACH EDGE
IDENTIFICATION OF WATERSHED FEATURES
Based on the two datasets each triangle is analyzed to find :
TRIANGULATED IRREGULAR NETWORK ( TIN )
EACH SINGLE TRIANGLE WILL BE
ANALYZED
The position vector ( r ) of a vertex with coordinates ( x ,y ,z ), where ‘v’ stands for A,B,C is given as
r = x i + y j + z k ….(1) Where, i ,j , k = triple orthogonal unit vectors, a, b, c = edge vectors, n = normal vector ,
k= vertical unit vector, h = horizontal vector, s = slope vector
I. CALCULATION OF PRICIPAL SLOPE VETOR OF A TRIANGLE
y
x
z
B
C
a
bA
h = k x n
kn
s
( x ,y ,z )
( x ,y ,z )(x ,y ,z )
cn = c x b
s = h x n
Fig. A representative triangular plane ABC with its projection on the horizontal Plane.
B BB
A A A C C C
v v v v
v v v v
II. DIRECTION OF SLOPE VECTOR RELATIVE TO THREE EDGES OF A TRIANGLE
For each triangle an edge code is defined in following way:Edge Code Criteria -1 If the slope vector start from the edge +1 If the slope vector ends towards the edge 0 If the slope vector is parallel to the edge
C
A
B
- 10
+ 1CASE 1
AC
-1
B
+1+1
CASE 2
C
B
A+1
-1 -1
CASE 3
Either of the following three cases might occur :
TRIANGULATED IRREGULAR NETWORK ( TIN )
EACH SINGLE EDGE COMMON TO TWO
TRIANGLES WILL BE ANALYZED
For identifying the type of the edge a counter,Type Code (TC) is introduced. TC, an array over all the edges, is kept zero initially.
-1 -1 -1 0
Ridge
+1 +1 +1 0
Channel
-1 +1
Flow Boundary
III. DIRECTION OF SLOPE VECTORS OF CONNECTED TRIANGLES FOR EACH EDGE
The final value of the TC of each edge defines the type of the edge:
Type Code (TC) Type of Edge less than zero ridge segment greater than zero channel segment equal to zero flow boundary segment
WATERSHED TERRAIN MODELLING
IDENTIFICATION OF WATERSHED FEATURES
(RIDGE, CHANNEL, FLOW BOUNDARY SEGMENTS)
IDENTIFICATION OF CHANNEL NETWORK
IDENTIFICATION OF OVERLAND FLOW CASCADES
LENGTH,WIDTH AND SLOPE OF CASCADE PLANES
I. NUMBERING THE CHANNEL SEGMENTS
II. IDENTIFYING THE CHANNEL CONFLUENCES IN THE CHANNEL NETWORK
III. IDENTIFYING CHANNEL SEGMENT WHICH IS CONNECTED TO CONFLUENCE AT ITS LOWER END
IV. CALCULATE TOTAL NUMBER OF CHANNEL REACHES
V. IDENTIFYING CHANNEL SEGMENTS MAKING UP A CHANNEL REACH
IDENTIFICATION OF CHANNEL NETWORK
WATERSHED TERRAIN MODELLING
IDENTIFICATION OF WATERSHED FEATURES
(RIDGE, CHANNEL, FLOW BOUNDARY SEGMENTS)
IDENTIFICATION OF CHANNEL NETWORK
IDENTIFICATION OF OVERLAND FLOW CASCADES
LENGTH,WIDTH AND SLOPE OF CASCADE PLANES
The overland flow through the connected triangles will follow the direction of Principal slope vector of the connected triangles. There can be three distinct possibilities :
I. Channel segments may get the entire flow of the connected triangles (When PSV meet the channel between its two ends)
II. Only part of the triangle contribute (When PSV meet the channel at its lower or upper end)
III. No lateral flow enters the channel ( When PSV is parallel to channel itself)
The triangle(s) connected to a channel segment may be further connected to triangles situated above by flow boundarysegments.The runoff from these triangles will contribute to the lateral flow of the channel segment. The overland flow contributing to channel segment is made up of cascade planes.
IDENTIFICATION OF OVERLAND FLOW CASCADES
CA
B
P
AC
B
P
CA
B
P
CA
B
Channel Segment
The geometrical shape of the plane of a cascade is trapezoidal or triangular. Theflow of water over each of these planes is one dimensional. For the computationof the flow variables in a series of planes, we replace the planes with conceptual cascade of rectangular planes whose length, width and slope could be calculated.
L3
L2
L1W1
W2
W3
CONCEPTUAL REPRESENTATION OF CASCADE PLANES
WATERSHED TERRAIN MODELLING
IDENTIFICATION OF WATERSHED FEATURES
(RIDGE, CHANNEL, FLOW BOUNDARY SEGMENTS)
IDENTIFICATION OF CHANNEL NETWORK
IDENTIFICATION OF OVERLAND FLOW CASCADES
LENGTH,WIDTH AND SLOPE OF CASCADE PLANES
yx
z
B
C
d
RA h
s
c
w
S
P
Q LENGTH
LENGTH, WIDTH AND SLOPE OF CASCADE PLANES
Fig. A representative triangular plane ABC with cascade plane PQRS
width ( w ) = d . h …………..(1) where
d = vector joining any two opposite sides of the plane ( say points P and Q)
h = unit horizontal vector
For the overland flow calculation it is assumed that plane PQRS is equivalent to the plane of the same area having length = (PQ+RS)/2 and width w.
The slope of the plane is that of the Principal Slope Vector of the triangle.If the unit slope vector is expressed by its vector components
s = s i + s j + s k ……………………………(2)
Then the slope of the plane ( tan 0 ) could be found as
tan 0 = s / s + s …………………………………(3)
x y z
z y x2 2
PART III : RUNOFF COMPUTATION FROM WATERSHEDPART III : RUNOFF COMPUTATION FROM WATERSHED
PART I : REPRESENTATION OF SURFACE GEOMETRY
PART II : WATERSHED TERRAIN MODELLING
FLOW CHART- METHODOLOGY
METHODOLOGY – PART IIIRUNOFF COMPUTATION FROM
WATERSHED
Fig. Overland flow towards a channel segment through corresponding connected triangles
Triangular Network
Source Area
Overland Flow
R A I N F A L L
I
N
F
IL T
RA
T
I
O
N
Fig. Conceptual representation of cascade planes
R A I N F A L L
I N F I L T R A T ION
So, n o Sc, n c
So= overland plane slopen o= Mannings’ roughness for overland planeSc= Channel slopen c= Mannings’ roughness for channel
TRIANGULATED IRREGULAR NETWORK ( TIN ) ON SOIL
LOHAMARA
RANGA
SERIES DOMINANT
TRIANGULATED IRREGULAR NETWORK ( TIN ) ON LANDUSE
DENSE FORESTWATER BODIESUPLAND WITHOUT SCRUBTREE/BUSHES/VILLAGELATERITIC UPLAND WITHOUT SCRUBOPEN FORESTKHARIF ONLYDOUBLE PADDY-POTATO
DOUBLE PADDY-PADDYDEGRADED FORESTDEGRADED ERODED/ SANDTRIANGULAR NETWORK
RUNOFF COMPUTATION FROM WATERSHED The general form of Kinematic Wave is expressed by the equation A = Area of watershed, channel
δA δQ δt δx …….(1)
Q = Discharge q = Lateral inflow per unit length x = Flow direction axis
For all x and t values, the discharge is describes as the function of “ area of flow” only
Q = α . Am ……..( 2) α ,m = KW routing parameter
In case of overland surface planes, The equation (1) and ( 2) modified asδh δq δt δx
α 0 , m = KW parameters of overland planes
where
α 0 = (S0 ) 1/2 / N N= overland roughness
m 0 = 5/3 ………..(5) S = Overland slope
In case of channels, Equation 1 holds good and equation 2 is rewritten as
Q = α k . Am ………….(6) α k , m = KW parameters for channel flow
Where S = Channel slope
α k = ……( 7) n = Channel roughness
m k = 5/3 …….(8)
A = Area of watershed, channel cross section areaQ = Dischargeq = Lateral inflow per unit lengthx = Flow direction axist = Time
q
ie ie= Rainfall excess depthh = depth of sheet flow
…..(3)
q = α 0 h m ……..(4)
S1/2
n1
B 2 h c 1 Z2
S = Channel slope, n = Channel roughnessB = Channel bed width, Z = Channel side slope h = Channel depth
MODEL APPLICATION
A model catchment has been selected along with assumed digital elevation data
6 : Total number of edges7 2.0 2.0 200 : Edge number with x,y,z coordinates8 4.5 3.0 2109 4.5 4.5 21510 2.5 6.5 21211 0.5 6.0 21512 2.0 4.0 2025 :Total number of triangles6 1 6 5 : Triangle number with vertices7 1 2 68 6 2 39 6 3 410 6 4 5
MODEL APPLICATION - DATA
MODEL APPLICATION – TRIANGULAR CHANNEL NETWORK
1
2
3
4
5
6
54
3
2
1
3500 m
0 m
3500 m
2500 m
1000 m
2500 m
1000 m
0 m
Triangular network of model catchment
12
3
10
2
10
3
8
6
5
9
4
7
Channel network of model catchment
Assumptions : A constant effective rainfall at a rate of 10mm/hr for duration of 30 minutes; Manning’s roughness coefficients for all triangular facets as 0.1 Infiltration rate as a constant 5mm/hr
Output : The discharge hydrographs at lowest nodes of the branches 1,2,3 of the model catchment have been shown in the figure below. The time step chosen is in the order of 10 seconds.
OUTFLOW
0
1
2
3
4
5
0 1 2 3 4 5 6
Time (hr)
Dis
char
ge
(C
um
ec.
)
Outflow (Reach 1)
Outflow (Reach 2)
Outflow (Reach 3)
MODEL APPLICATION – RESULTS
GRAPHICAL USER INTERFACE GRAPHICAL USER INTERFACE (GUI)(GUI)
The development environment of the proposed catchment model is Visual Basic Professional version 6.0 operating under Microsoft Windows 98/NT.The model employs standard Windows controls ( menus, frames, command buttons, radio buttons etc.) and dialogs , thereby providing the users with a familiar graphical user interface environment.
GRAPHICAL USER INTERFACE (GUI)
GRAPHICAL USER INTERFACE (GUI)
MODEL UTILITY MODEL UTILITY
FOR FOR
PRACTICAL APPLICATIONSPRACTICAL APPLICATIONS
Data obtained by running the model may be used on certain water resources projects.
Bridges, Culverts and Aqueducts:
Design of cross drainage structures like the above requires, among other data, the linear waterway and high flood level (HFL)anticipated. The proposed model will help to estimate the flood Discharge corresponding to a given return period at the point of interest in the catchment. By working out the maximum discharge anticipated at a certain location of a river the waterwayand HFL may easily be found out provided the cross section of the river at that location is known.
Spillways for small dams:
Applying the design storm over the catchment, the peak flood at the point of interest could be obtained which, in turn could be used to decide the width of a spillway bay, number of bays and other parameters of the spillway.
Levees for flood protection:
In this case the flood simulation should be run initially assuming no levees and then run for different location and heights of the levees. The optimum levee height should be one that is Just about 1 to 1.5 meters above the high flood level at various points along the river.
MODEL UTILITY FOR PRACTICAL APPLICATIONS
MODEL UTILITY FOR PRACTICAL APPLICATIONS
Predicting erosion potential due to land use change:
The proposed model gives the discharge along with the water depths at various nodal points in the catchment. These values could also be used to estimate land erosion after coupling with suitable sediment transport model.
Site planning for micro hydels:
The proposed model could assist the regional planners in getting the discharge value at the point of interest which in turn helps
in estimating the power available from the discharge as well as selection of turbine to be used in power generation.
Agriculture:
Agriculture being our mainstay, optimum land use planning has also to consider availability of natural water resource in the system not by inducing surface irrigation but through introducing natural check - dams and appropriate water harvesting structures so that progressive availability of water in the root zone, as soil moisture in the surface and subsurface zones becomes possible. Introducing appropriate crop geometry with intermittent short, long and transverse as well as lateral root crops, particularly in the lean months cultivation programmes would enable a better productivity of the land parcel.Even cropswhich require less water and fertilizer for growth could also be actively promoted.
Akan, A.O. and Yen, B.C. 1981. Diffusion wave flood routing in channel networks, J. Hyrd. Engineering, ASCE, (107), 719-732.
French. Richard H. 1986, Open Channel Hydraulics, Chapter 4. McGraw Hill Publication.
Garg, N K and Sen, D. J. 1994. Determination of watershed features for surface runoff model Journal of Hydraulic Engineering, ASCE, 120(4), 427-447.
Garg, N K and Sen, D. J. 2001. Integrated physically based rainfall-runoff model using FEM. Journal of Hydrologic Engineering, ASCE, 6(3), 179-188.
Hossain, M.M. and Mathur, B.S. 1994. Runoff Computations from semi- hilly tropical watersheds using Simple Kinematic Wave Theory.
Kuichling, E. 1889. The relation between the rainfall and the discharge districts. Trans.Amer. Soc.Civil Enngrs., (20), 1-56
Mutreja, K N. 1986. Applied Hydrology.Tata McGraw Hill, India.
Ponce Miguel Victor 1989. Engineering Hydrology Principles and Practices, Chapter 9 and 10. Prentice Hall, Inc.,
Raudkivi, A.J. 1979. Hydrology: An introduction to hydrological processes and modelling. Pergamon Press, U.K.
REFERENCES
Sen D.J. 1985. A Study of Terrain Modelling and Finite Element based Watershed dynamics, PhD. Thesis, Department of Civil Engineering, Indian Institute of Technology, Delhi.
Singh, V.P. 1989. Hydrologic Systems, rainfall runoff modelling, Vol. I. Englewood Cliffs, N.J., Prentice Hall.
Viessman, W., Jr., Lewis, G.L. and Knapp, J.W. 1989. Introduction to Hydrology. Harper and Row Publ., Singapore
Wooding, R.A. 1965. A hydraulic model for the catchment- stream problem, Part I, Kinematic wave Theory. Journal of hydrology, Vol. III., Nos. 3/4 pp. 254-267.
Wooding, R.A. 1965. A hydraulic model for the catchment- stream problem, Part II, Numerical Solutions. Journal of hydrology, Vol. III., Nos. 3/4 pp. 268-262.
Woolhiser, D.A. 1975. Simulation of unsteady overland flow, Chapter 12, Unsteady Flow in open channels, Vol. II, Water Resource Publication.
Yen, B.C. and Akan, A.O. 1976. Flood routing through river junctions”, in Rivers’76, Vol. I, ASCE, 212-231.
REFERENCES
The proposed work for all its smallness owes a lot to a large number of people, first and foremost being Dr. S. Sengupta, Professor, Dept. of Geology and Geophysics, Indian Institute of Technology, Kharagpur, India my guide and supervisor to whom I owe a debt of gratitude for his perseverance in guiding me throughout the course of this work. His perceptual inspiration, encouragement and understanding have been a main stay of this work.
I would like to express my profound gratitude to my co-guide Dr. D.J.Sen, Assistant Professor, Dept. of Civil Engineering, Indian Institute of Technology, Kharagpur, India for his constant supervision, valuable guidance and unfailing encouragement during the course of the present work. His patience, co-operation and personal attention is always a source of motivation for me. The algorithms used for determination of watershed features for surface runoff model are one of the major contributions from him in this proposed model. I am indebted for his kind help, assistance and support which made it possible for me to standup to the challenge offered by the task and come out successfully.
ACKNOWLEDGEMENT
It is incumbent on me to mention Dr. Parthosarathi Chakrabarti, Principal Scientist, Department of Science and Technology, West Bengal who showed keen interest in solving my difficulties and took pains to go through the entire work of this presentation in spite of his busy schedule and other important engagements
And
I must acknowledge the generous assistance and valuable suggestions I got each moment from my beloved wife Mousumi while preparing this presentation.She always remains as a constant source of inspiration for doing this project for the benefit of people.
ACKNOWLEDGEMENT
Thank You