PROPOSED DREDGING OF ISLA BACSAN

ALONG THE CAGAYAN DE ORO RIVER

_______________________

AN UNDERGRADUATE RESEARCH PROPOSAL

Presented to

The Faculty of the Department of Civil Engineering

Mindanao University of Science and Technology

Cagayan De Oro City

______________________

In Partial Fulfillment

of the Requirements for the Degree of

BACHELOR OF SCIENCE IN CIVIL ENGINEERING

MARYJUN A. COSARE

RENECO P. RAGMAC

JOEL G. SAJOL

IRENE B. SOMOBAY

CHAPTER I

INTRODUCTION

1.1 General Introduction

Silt is sediment consisting of small sized particles of rock. It comes from the breakdown

of rocks and gravel in the upper river sections, from overland flow across soils in the fields and

from outfalls draining urban areas .It is naturally transported in a river, during a flood when the

river flow fast, silt moved within the water. After flood, silt is deposited on the river channel bed

when the river flows slowly. Dredging is the process of removing silt from the bottom and sides

of the river channel. Is to prevent flooding where equivalent to squeeze the volume of water held

by a floodplain within the volume of water held in the river channel, during major floods the

river cannot be contained within the normal river channel. River dredging is primarily

undertaken to improve navigation, by increasing depths and straightening channels, to improve

land drainage, particularly by creating artificial channels and for commercial dredging is

undertaken to acquire sand and gravels for construction sites (The Environment Agency,(2012).River

Dredging and Flood Defence To Dredge or Not to Dredge? Retrieved August 10, 2012, from

http://www.enquiries@environment-agency.gov.uk)

In worldwide, dredging is rarely on people list of life-changing technologies. Yet,

without dredging, supply lines for hundreds of thousands of products would be shut down. Many

of our ports and waterways would quickly become not traversable, and much of the recreation

and tourism made possible by our seashores, lakes and rivers would slowly diminish and finally

cease as beaches eroded, lakes filled in, and rivers changed course. The construction industry

would be severely hampered by lack of inexpensive sand and gravel, and many civil works

projects including important bridges and reservoirs would be impossible.

In the Philippines, dredging activities are practiced to get the silt filled in the river

channel. Since, dredging project is a quite expensive work, government select only the rivers that

need most of dredging work. One of the rivers which are located in Northern Mindanao Region

is the Cagayan de Oro River, which had not yet implements dredging maintenance. As years

goes by, the siltation process in the channel bed formed a small silted lands in the river. One of

the silted lands was so called the Isla Bacsan.

Isla Bacsan is located approximately at 8 ° 29’N and 124° 38’E on the world map. It

situated between Marcos and Puntod-Kauswagan Bridge of the city. Based on the record

surveyed from the Department of Environment and Natural Resources, Isla Bacsan measures the

area of silted land covers about approximately 3.2 hectares. The longest length and width of the

silted land is approximately 530 meters and 80 meters, respectively.

This silted land contains vegetation such as trees and plants that stabilize the strength of

the soil. Furthermore, the land now becomes a barrier to the flow of the river. When heavy rain

fall due to a storm and a typhoon, the water in the river will overflows and tends to find low

lying areas cause flooding at its adjacent area, where residents lived.

In such case, the proponents will study and will provide the dredging project estimate

cost of Isla Bacsan in Cagayan de Oro City with the best method of an essential and an

economical dredging.

1.2 Statement of the Problem

This study intends to investigate the actual estimated cost of Dredging in Isla Bacsan,

Cagayan de Oro River. This study seeks to answer the following question:

1. Why we need to dredge the Isla Bacsan area?

2. What method will be used to determine the volume of Isla Bacsan?

3. What method of dredging will be capable on this project?

4. What will be the uses of dredge materials?

5. How much is the total estimated cost of this project?

1.3 Objectives of the Study

The main objective of this study is to determine the cost of dredging of Isla Bacsan

along Cagayan De Oro River. Specific objectives include:

1. To calculate the volume of Isla Bacsan.

2. To determine the best suitable dredging method of Isla Bacsan.

1.4 Significance of the Study

The purpose of this study is to establish a guide and reference for the future researchers

regarding the dredging of islet in the river. It provides methods of implementation and

calculations of data that have been gathered. It will give an actual survey of Isla Bacsan area and

will provide the actual estimating measures about dredging works.

1.5 Scope and Limitation

This study will focus on the actual estimated cost of dredging project of Isla Bacsan

situated in Cagayan de Oro River. In line with this, the raw data will be gathered at the site:

THE SITE

Fig.3. Area of Proposed Isla Bacsan Dredging ProjectSource: Google Earth ©2012 and Image 2012 Digital Globe

This study will not cover the discharge of the river and any other areas that are not

stated and specified to be covered by the study.

1.6 Terminologies

Dredging. An underwater excavation for the purpose of navigating waterways, increasing

depth and straightening channels.

Flood Plain. An area of low lying ground adjacent to a river that is subject to flooding.

Geographic Information System (GIS). A system designed to capture, store, manipulate,

analyze, manage, and present all types of geographical

data.

Google Earth Program. A virtual globe, map and geographical information program that

maps the Earth by the superimposition of images obtained from

satellite imagery, aerial photography and GIS 3D globe.

River Channel bed. The bottom part of the river which is usually composed of sediments and

saturated soil.

Silt. A sedimentary material consisting of grains or particles of disintegrated rock, smaller

than sand and larger than clay. The diameter of the particles ranges from 0.0039 to

0.0625 mm. Is often found at the bottom of bodies of water where it accumulates

by settling through the water.

CHAPTER II

REVIEW OF RELATED LITERATURE

This chapter sites relevant information related to the study. This includes a memorandum

for the regional executive director DENR, Region-10, Macabalan Cagayan de Oro which subject

entitled “Ownership of the Land within the Existing Islets along the Cagayan de Oro”.

Cagayan de Oro River Islets and Related Problem Issues

Based on the Department of Environment and Natural Resources (DENR), there are five

(5) unsurveyed islets along Cagayan de Oro City River namely: Isla de Oro measures 8.6 ha, Isla

Delta measures 1.3 ha, Isla Delta 2 measures 1.2 ha, Isla Bugnaw measures 1.4 ha, and Isla

Bacsan measures 3.2 ha; with an approximate total area of 15.7 hectares. The City Council of

Cagayan de Oro passed Resolution No. 7733-2006 dated January 30, 2006 requesting a

proclamation declaring and granting ownership of the islets in favor of the City to be used for

eco –tourism project and other public purpose with parallel request of Isla Delta Landless

Association, Inc (IDLAI). On June 4, 2008, regional Executive Director, Maximo O. Dichoso, in

a letter to City Mayor Constantino G. Jaraula, denied the request on the ground that the islets do

not qualify for eco-tourism purposes. On October 2, 2008, Regional Executive Director Maximo

O.Dichoso, in a letter to City Councilor Reynaldo N. Advincula, Chairman of the Committee on

Subdivision and Landed Estate, again denied the request due to the nature of accretionary islets

and its inherent instability. Further, prior geo-scientific studies confirmed the active and dynamic

nature of this fluvial system and it would be prudent to avoid construction of houses near the

river to avert potential catastrophic events. On January 19, 2009, Atty. Ernesto D. Adobo, Jr,.

Then DENR-10 Regional Executive Director, for the third time denied the request of the City

Government of Cagayan de Oro and reiterated the recommendations of the Committee in a letter

to City Mayor Constatntino G. Jaraula. See Appendix _ on page _ for the complete information

about the memorandum.

On September 10, 2011, the OIC Regional Director from Mines and Geosciences Bureau

Regional Office 10, replied a memorandum (See Appendix C) to the Director of Mines and

Geosciences Bureau (MGB) in Quezon City regarding the issuance of advisories and warnings

on geo hazards to all government units for the purpose of taking action of the announcement by

the PAGASA about the expected landfall of stronger typhoons from September to December on

year 2010. In December 16, 2011, Typhoon Sendong made a landfall in Northern Mindanao. The

situation in Cagayan de Oro on that fateful date was that there was incessant rain in the

mountains of Bukidnon, and Cagayan de Oro River was the recipient of the huge volume of the

rainwater. In such case, the capacity of the river was lesser than the volume of rainwater. With

this, the river overflows. Cagayan de Oro City alone it was reported that 677 people were killed.

If the casualty of the neighboring city of Iligan is included, the total number of killed is 1,249.

Many people are still missing and thousands of persons are dislocated.  It was more unfortunate

that the flashflood came when the sea was at high tide thus making it hard for the water in the

river to drain into the sea (author, year).

River Maintenance

Maintenance dredging is one of the solutions of the city government to undertake in

avoiding these disasters. Dredging the silts and removing the islets could provide straightening of

the water flow and deepen the river so that the overflowing of the river could be minimized or

further eliminated.

Dredging is really important especially on the heavily silted river. When one strong

typhoon will come and the people in the banks of the river shall be in big trouble. When the river

overflows, thousands will be displaced. Business community stated that the flooding discouraged

investors to expand their ventures in Mindanao. Cotabato City Vice Mayor Muslimin Sema

stated also that we need to do something, not just warn the people. We have to dredge the

downstream channel of the Rio Grande de Mindanao that straddles through Cotabato City

(author, year).

The concept of dredging as alternative if not an effective strategy in addressing hazards

like flooding and erosion in major river systems in the region has been proposed by the Mines

and Geo-Sciences Bureau (MGB) of  the Department of Environment and Natural Resources -1

(MGB-DENR-1) in a forum. This non-structural method and mitigating measure is cost-effective

as against infrastructure intervention which costs millions of pesos yet not fully effective (author,

year).

 (W.J.Vlasblom, 2003) stated that dredging equipment can be divided in Mechanical

Dredgers and Hydraulic Dredgers. The differences between these two types are the way that the

soil is excavated; either mechanical or hydraulic. Mechanical Dredgers are the Bucket Ladder

Dredge, Grab Dredge, and Dipper and Backhoe Dredge while hydraulic dredgers are Plain

Suction Dredge, Cutter Dredge, and Trailing Suction Hopper Dredge. All dredgers except the

trailing suction hopper dredgers are stationary dredgers, which mean that they are anchored by

wires or (spud) poles. Every type of dredger has its own applied working area in which its

production is optimal in a technical way as well as in an economical way. It will be clear that the

boundaries of these applied working areas are not strictly determined, but are also determined by

other working conditions, which can differ from job to job. In the table below, the possibilities of

the different types are shortly summarized.

Table 1.Types of dredgers and its working area and method

In

References

J.Gunsch. (2012, May 24). What is dredging? Retrieved August 7, 2012, from Wisegeek:

http://www.wisegeek.com/what-is-dredging.htm

Steering Committee. (2009). Ownership of the land within the existing islets along the

Cagayan de Oro river. Cagayan de Oro City: DENR-10.

W.J.Vlasblom. (2003). Introduction to Dredging Equipment, lecture notes distrubuted in

Designing Dredging Equipment w3408B at the Delft Universiy of Technology,The

Netherlands

Wikipedia Contributors. (2012, July 29). Dredging. Retrieved August 6, 2012, from In

Wikipedia, The Free Encyclopedia: http://en.wikipedia.org/w/index.php?

title=Dredging&oldid=504722900