CASC2D: Hydrologic Modelling
Entry ID: CASC2D
Abstract: CASC2D is a fully-unsteady, physically-based, distributed-parameter, raster
(square-grid), two-dimensional, infiltration-excess (Hortonian) hydrologic
model for simulating the hydrologic response of a watersheds subject to an
input rainfall field. Major components of the model include: continuous
soil-moisture accounting, rainfall interception, infiltration, surface and
... channel runoff routing, soil erosion and sediment transport. CASC2D development
was initiated in 1989 at the U.S. Army Research Office (ARO) funded Center for
Excellence in Geosciences at Colorado State University. The original version of
CASC2D has been significantly enhanced under funding from ARO and the U.S. Army
Corps of Engineers Waterways Experiment Station (USACEWES). CASC2D has been
selected by USACEWES as its premier two-dimensional surface water hydrologic
model, and is one of the surface-water hydrologic models support by the the
Watershed Modeling System (WMS) under development at Brigham Young University.
CASC2D is a state-of-the-art hydrologic model that takes advantage of
recent advances in Geographic Information Systems (GIS), remote sensing, and
low-cost computational power. Compared with the USACE standard practice surface
water hydrology model HEC-1, CASC2D offers significant improvements in
capability. HEC-1 requires the division of study watersheds into sub-catchments
that are assumed to be hydrologically uniform, while CASC2D allows the user to
select a grid size that appropriately describes the spatial variability in all
watershed characteristics. Furthermore, CASC2D is physically-based; CASC2D
solves the equations of conservation of mass and energy to determine the timing
and path of runoff in the watershed. More traditional approaches such as HEC-1
rely on more conceptualizations of runoff production. The physically-based
approach is superior when the modeler is interested in runoff process details
at small scales within the watershed. Physically-based hydrologic models are
also superior when trying to predict the behavior of ungaged watersheds where
calibration data do not exist.
CASC2D is fully spatially-varied at a user specified resolution (typ.
30-200 m) and therefore requires considerably more input data than HEC-1.
Spatially-distributed modeling offers the capability of determining the value
of any hydrologic variable at any grid-point in the watershed at the expense of
requiring significantly more input than traditional approaches. CASC2D readily
accepts spatially-varied input in any watershed or rainfall input, however,
input data uncertainty may result in a non-unique calibration.
CASC2D has a large number of input and output options. The WMS interface
for CASC2D is valuable because it separates the user from issues related to
input file formatting, and guides the user through model set-up and option
selection. WMS does not, and is not intended to, replace the full functionality
of a Geographic Information System (GIS). The GRASS GIS developed by the U.S.
Army Construction Engineering Research Laboratories is very helpful in the
preparation of CASC2D data sets. CASC2D relies on the GRASS ASCII data file
format for storing all spatially-distributed variables. The WMS interface can
directly access data from both the ARC/INFO and GRASS GIS systems and export
data to CASC2D.
[Summary provided by Fred Ogden.]
ISO Topic Category
Use Constraints Users with no background in or understanding of distributed hydrology are
strongly advised against using this code in any mode, particularly in
operational mode. Besides knowledge of basic hydrology, experience with typical
numerical techniques used in physically-based hydrodynamic models is
recommended as it will help the user grasp capabilities and ... limitations of this
model. This manual is significantly condensed for electronic distribution and
is in no way comprehensive. Users are encouraged to experiment with the model
and venture in hydrology textbooks and journal papers to learn more about the
topics touched upon in this manual. The r.hydro.CASC2D code is continuously
being improved. Changes in the source code of r.hydro.CASC2D may be made at any
time, without notification. No claims are made regarding the suitability of
r.hydro.CASC2D for any particular purpose. The model r.hydro.CASC2D was written
for research and educational purposes.
Bras, R. L., 1990, Hydrology: An introduction to hydrologic science,
Addison-Wesley, Reading, Mass., 643 p.
Crum, T. D., and R. L. Alberty, 1993, The WSR-88D and the WSR-88D operational
support facility, Bulletin of the American Meteorological Soc., 74(9), pp.
Cunge, J.A., F.M. Holly, and A. Verwey, 1980, Practical Aspects of
... Computational River Hydraulics, Iowa Institute of Hydraulic Research, 404HL The
University of Iowa, Iowa City, IA 52242. 420 p.
Gray, D.M., 1970, Handbook on the Principles of Hydrology, National Research
Council of Canada, Water Information Center Inc., Water Research Building,
Manhasset Isle, Port Washington, N.Y., 11050.
Julien, P. Y., and B. Saghafian, 1991, CASC2D users manual - A two dimensional
watershed rainfall-runoff model, Civil Engr. Report, CER90-91PYJ-BS-12,
Colorado State University, Fort Collins, CO.
Julien, P. Y., Saghafian, B., and F. L. Ogden, 1995, "Raster-Based Hydrologic
Modeling of Spatially-Varied Surface Runoff", Water Resources Bulletin, AWRA,
31(3), pp. 523-536.
Ogden, F.L., 1994, de-St Venant channel routing in distributed hydrologic
modeling., Proc. Hydraulic Engineering `94, ASCE Hydraulics Specialty
Conference, G.V. Cotroneo and R.R. Rumer, eds., Vol. 1, pp. 492-496.
Ogden, F.L., Saghafian, B., and W.F. Krajewski, 1994, GIS-based channel
extraction and smoothing algorithm for distributed hydrologic modeling, Proc.
Hydraulic Engineering `94, ASCE Hydraulics Specialty Conference, G.V. Cotroneo
and R.R. Rumer eds., August 1-5, 1994, Buffalo, N.Y., pp. 237-241.
Rawls, W. J., Brakensiek, D. L., and N. Miller, 1983, Green-Ampt infiltration
parameters from soils data, J. of Hydraulic Engineering, ASCE, 109(1), pp.
Rawls, W. J., Brakensiek, D. L., and K. E. Saxton, 1982, Estimation of soil
water properties, Trans. of ASAE, pp. 1316-1320.
Saghafian, B., 1992, Hydrologic analysis of watershed response to spatially
varied infiltration, Ph.D. Dissertation, Civil Engr. Dept., Colorado State
University, Fort Collins, CO.
Saghafian, B., 1993, Implementation of a distributed hydrologic model within
Geographic Resources Analysis Support System (GRASS), Proceedings of the Second
International Conference on Integrating Environmental Models and GIS,
Smith, R. E., Corradini, C., and F. Melone, 1993, Modeling infiltration for
multistorm runoff events, Water Resources Research, 29(1), pp. 133-144.
Creation and Review Dates