Geoscience Reference
In-Depth Information
1 Introduction
Basically, Geographic Information System (GIS) can be defined as a designed
system to capture, manipulate, analyse, manage and present all kinds of geo-
graphical or spatial data in various mediums such as map and model to help the
decision making process. People from various professions mostly consider GIS as
a tool to help them in providing reliable spatial information to support their work,
such as in planning and managing environment, urban, engineering, hydrology,
geology, etc (Hengxing et al.
2008
; Bernard et al.
2010
).
The spatial information provided by GIS is not limited only for the ground
entity or object, but it can extend up to above the ground (atmosphere or space)
and as well as beneath ground surface. For example, water flow direction infor-
mation can be either on surface flow direction (which came from rain or flood)
model or underground water movement for underground water modelling.
Whereas, this study is only concerned with surface water flow direction modelling
in order to assist and provide more accurate spatial information to hydrology field.
Water flow directions are commonly used in digital elevation models (DEMs)
for hydrology applications to estimate and model the paths of water toward the
streams, sedimentations and contaminant movement (Tarboton
1997
). DEM is a
preferred medium because it consists of an efficient, readily available and com-
pletely matrix data structure (Miller
2010
; Moore et al.
1991
).
Many algorithms available today define the processes of water flow in different
approaches to fit their targeted applications. Examples of applications that require
crucial decisions are drainage network planning, flood prediction, monitoring and
precaution, dam planning and construction, water catchment and others. In short,
flow direction algorithms can be divided into two main categories: Single Flow
Direction (SFD) and Multiple Flow Direction (MFD). The famous SFD is the
simplest D8 algorithm while D-infinity (D?) represents the most popular algo-
rithm in MFD.
1.1 Problem Statement
The term water flow direction is actually a basic technique in watershed analysis
especially used in GIS and other professional fields related to surface water flow
direction modelling. In order to provide the most accurate information on water
flow direction and watershed model, many new data acquisition techniques have
been introduced and the older systems had evolved dramatically (new hardware,
software and procedures) to increase the efficiency and accuracy of the output
result.
For example, Airborne Light Detection and Ranging (LiDAR) is used as a new
data acquisition technique (compared to traditional surveying and mapping
methods) especially in GIS and other construction fields for sub-meter accuracy of
