A GIS-RS COMPATIBLE RAINFALL-SURFACE RUNOFF MODEL FOR REGIONAL LEVEL PLANNING.

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

QQ

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 )


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


Based on the two datasets each triangle is analyzed to find :


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 :


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

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


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.


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

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


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.



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

A GIS-RS COMPATIBLE RAINFALL-SURFACE RUNOFF MODEL FOR REGIONAL LEVEL PLANNING.

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