A Cell to Cell Routing ModelA Cell to Cell Routing Model

By : Rajeev Raina

CVEN 689 Civil Engineering Applications of GIS

Instructor : Dr. Francisco Olivera

Topics of DiscussionTopics of Discussion

1. Introduction

2. Significance of this work

3. Methodology

4. Goals Ahead

IntroductionIntroduction

What is a Cell to Cell routing model?1. It’s hydrological routing model.

2. Calculates the storage and the flow at any instant

at any point in the watershed.

3. A model that divides the watershed into

small cells which can be approximated as linear

reservoirs.

4. These cells are further divided into small tanks

The Linear ReservoirThe Linear ReservoirInflow (I)

Outflow (Q)

Q

T

SignificanceSignificance This model divides this linear reservoir

into a cascade of small reservoirs

So what's the advantage of this algorithm?Q

T

SignificanceSignificanceNow the stream network in a watershed can be represented like this

ParametersParametersHere is the hydrology for the model

1. Storage (S) α [Initial storage (So), Runoff (R) ,Inflow(I),Outflow(O)]

2. Outflow = S*V/Reach (Reach = Flow length, V = Velocity of flow)

3. K = Reach / V ( K = Storage constant)

4. N = No of Small Tanks N = V*Reach / 2*D (D= Coefficient of Dispersion)

N < 36 K2/ (ΔT) 2 (ΔT = Time Step given by the User)

5. k = K / N

DataData

1. 500 meter DEM of the United States (From USGS)

2. Real time Runoff data

Methodology1. Clip the source DEM to the size that required for the study.

2. To Fill the DEM for fill all the Sinks that had been created by means other than natural means.

3. To find the flow direction grid from the given DEM

4. To find the flow accumulation grid

5. To find the stream network

6. To delineate the watershed

7. To overlay the watershed with a mesh

8. To Transfer the flow properties of the stream to the mesh.

9. Use the mesh with modified properties to calculate the storage and flow

Processing the DEM

This is the DEM that I obtained after filling the sinks.

The DEM the I had was a 500 m DEM of the United States. This was clipped to obtain the area that is there covered by the Brazos basin

Flow Direction and Flow Direction and Accumulation GridsAccumulation Grids

The Flow direction and accumulation grids were obtained by running the AML commands Flowdirection and Flowaccumulation

Stream NetworksStream Networks

The Streams grid was obtained by giving the condition that the streams with the flow from more that 100 streams upstream be included.

Watershed Delineation and Watershed Delineation and addition of a bufferaddition of a buffer

1. Once the stream network was obtained we delineated the water shed.2. Then a buffer with a distance of 50 km from the watershed boundary was marked just for the purpose of ensuring that we didn’t lose any data3. Then a mesh of cell size 10 *10 miles was over laid on the buffer.4 This mesh was made to intersect with the buffer using an AML.5. The output of this process is a table with the following attributes: Recno., Length,Fnode,Tonode,Meshid

Processing the ResultsProcessing the Results

1. The Upstream flow length and Order program

2. The Output Table

-Attributes : BoxId, DSboxID, Area, Reach, FDBoxID

3. Checking the Table for Inconsistencies and Errors

4. Correcting the Errors manually

Flow direction, Flow accumulation and Flow direction, Flow accumulation and

Stream network grids for the meshStream network grids for the mesh

Flow direction

Flow Accumulation

Stream Network

Fixing the outlet for the BrazosFixing the outlet for the Brazos

1. The point selected was the end of the main stream. 2. This was added as a point theme and then converted into a grid.

Watershed DelineationWatershed Delineation

Using the outlet and the flow direction grid of the mesh the watershed was delineated.

Comparison with the earlier Comparison with the earlier generated Watershedgenerated Watershed

Once the water shed that we got from the mesh and that of the stream earlier was compared we find that they matched pretty well.

Visual Basic CodeVisual Basic Code

1. Developed a visual basic code which calculates the storage and the flow.

2. This input for this program will be the table in comma delimited format which we got from the watershed generated earlier and so will be the output.

3. The user is asked for a input time step which is used for the calculation of N ( the number of small tanks)

4. The program then gives the user reports that could be weekly/daily/hourly or as desired.

Goals AheadGoals Ahead

1. To test the model.

2. To make a query attachment that will give the user

precise data that he/she wants.

Questions ??Questions ??

Thank YouThank You