An Overview of Hydrological modelling & HEC-RAS(River Analysis System) is covered in this presentation.

1. Prepared By:
VISHVAM PANCHOLI
(130280712013)
ME-Water Resources & Management
L.D.College of Engineering,Ahmedabad-380061

2. Outline of seminar
*Basic Concept of modelling
*Introduction of modelling
*Introduction to HEC RAS Model
*Overview of HEC RAS Model

3. What is
Hydrological
modelling

4. Hydrologic models are simplified, conceptual representations of the
Hydrologic cycle.
Source:- U.S.D.S

5. Why Modelling is Required ?
Modelling has become an integral part of the decision making
process for water engineers and managers.
Recent research in hydrologic modelling tries to have a more global
approach to the understanding of the behaviour of hydrologic systems to
make better predictions and to face the major challenges in water
resources management.
Recently, Hydrological models have taken over the most important tasks in
problem solving in hydrology (UNESCO, 1985). It is valuable for studying
potential impacts of changes in land use or climate.
As one report of CSDMS ( Community Surface Dynamics Modelling
System) 56 Hydrological models are Present.

6. What are the use of a model?
Forecast / Prediction
Instead of expensive and time consuming measurements
What happens if’ questions
Summarize and test knowledge
Education

7. Hydrological
Modelling
Black Box
Conceptual
Deterministic
Lumped
Semi-
Distributed
Distibuted

9. 1).Lumped models
Do not account for the spatial distribution of input variables or
parameters.
Do not require a digital elevation model (DEM) as input.
Also Known as “Low Rank” Models.
Ex- SRM (Snowmelt-Runoff Model), WATBAL etc.
2).Semi-distributed models
Models Parameters are partially vary in space by dividing the basin into
sub basins.
It has Two types
1) Kinematic wave theory models (KW models, such as HEC-HMS),
2) Probability distributed models (PD models, such as TOPMODEL).

10. The KW models are simplified versions of the surface and/or subsurface
flow equations
The PD models are accounted distributions of input parameters across the
basin.
Also Known as “Medium Rank” Models.
Ex-HEC-HMS,HEC-RAS, Storm Water Management Model (SWMM),
TOPMODEL.
3).Distributed models
Parameters are fully allowed to vary in space.
It require large amounts of (often unavailable) data.
Distributed models require a DEM as input.
Also Known as “High Rank” Models.
EX-MIKE11/SHE, WATFLOOD etc.

11. Introduction to HEC RAS

12. HEC-RAS
(Hydrologic Engineering Centers River Analysis System)
HEC-RAS is a one-dimensional flow hydraulic model designed to
aid hydraulic engineers in channel flow analysis and floodplain
determination.
HEC-RAS program was developed by the US Army Corps of
Engineers to manage the rivers, harbors,other public works under
their jurisdiction.

13. HEC-RAS model offering a simple way to set model parameters and
a graphical user interface(GUI) to run the model and visualize the
results.
River Analysis
Water depth
Flow

14. Use of HES RAS
Water flowing through systems of open channels ;
Computing water surface profiles.
Floodplain management ;
Flood insurance studies to evaluate floodway encroachments.
Additional uses
 Bridge and culvert design and analysis,
 Levee studies,
 Channel modification studies,
 Dam breach analysis.

15. Graphical User Interface(GUI)
Data storage/management Graphics,
Tabular Output & Reporting
GeoRAS – GIS pre and post processor

17. Steady flow is the solution of the one-dimensional energy equation.
The momentum equation may be used (include hydraulic jumps,
hydraulics of bridges, and evaluating profiles at river confluences)where
the water surface profile is rapidly varied.

19. Unsteady flow is based on solution of 1-D Saint Venant Equation
using an finite difference method.
It is capable of modelling subcritical, supercritical, and mixed flow
regime flow along with the effects of bridges, culverts, weirs, and
structures.

21. Advantages :-
It support by the US Army Corps of Engineers, also acceptance by
many government agencies and private firms.
It is in the public domain and peer-reviewed,
available to download free of charge from HEC's web site.
Various private companies are registered as official "vendors" and
offer consulting support and add on software.
Limitations :-
Steep bed slopes (HEC RAS User's manual says >10%);
multi-dimensional flow characteristics;
complex pipe systems.
Large Data Accuracy Required

22. The HEC-RAS (4.1) Software New Features:
(1) Steady flow water surface profile computations;
(2) unsteady flow simulation;
(3) Movable boundary sediment transport computations;
(4) New RAS mapper floodplain delineation capabilities;
(5) Hydrologic routing reaches within an unsteady flow model run;
(6) Groundwater leakage for storage areas;
(7) Water quality modelling enhancements.

23. *
http://www.hec.usace.army.mil
http://csdms.colorado.edu/wiki/Hydrological_Models
http://en.wikipedia.org/wiki/HEC-RAS
http://www.forrex.org
http://www.eng.uwo.ca/research
http://www.fema.gov