ALB's Nature Journal

Aloha! Welcome to ALB's Nature Journal. I hope that this site will become useful for both you and I. Throughout the spring 2006 semester, I hope to become excited and intreged about the world of science. I look forward to this class sparking an interest in this field and help me to learn new fun and enjoyable ways of teaching science.

Thursday, March 16, 2006

A Dam?

After hearing about the tragedy that struck Kaua'i on Tuesday, I began thinking what is a dam and why are they used?

A dam is a structure built across a river to hold back water for a variety of reasons, including protecting areas from floods, storing water creating a lake or reservoir, and generating power. Most dams have a section called a spillway which is intended that water will flow either sparitically or continuously.

Based on the structure and material used, dams are classified as timber dams, embankment dams or masonry dams (either of the gravity or arch type), with several subtypes.

A diversionary dam is a structure to divert a portion river.
Timber dams were used in the early part of the industrial revolution and in frontier areas due to ease and speed of construction.
Embankment dams are made from compacted earth, and have two main types, rock-filled and earth-filled dams. Embankment dams rely on their weight to hold back the force of water, like the gravity dams made from concrete.
Earth dams are made of rolled-earth and earth-filled dams, are constructed of well compacted earth.

A spillway is a section of a dam designed to pass water from the upstream side of a dam to the downstream side. Many spillways have floodgates designed to control the flow through the spillway. Any cavities or turbulence of the water flowing over the spillway slowly eats the dam. This is exactly what sounds like happened at the Koloko dam in Kaua'i.

According to an article that was posted on October 23, 2005, civil engineers reported 22 of Hawaii dams as having deficiencies that raise safety concerns. Nearly all of Hawaii's dams are earthen structures erected early in the past century. They were build before federal standards existed and long before Hawaii created a state office for assessing dam and levee safety.

According to the infrastructure report card 2005, Hawaii has 22 state-determined deficient dams and 77 high hazard dams. A high hazard dam is defined as a dam whose failure would cause a loss of life and significant property damage.

High-hazard dams include Nuuanu Dam on Oahu, Lakalea Reservoir on the Big Island, Homer Reservoir on Maui and Lower Kapahi Reservoir on Kauai. Interesting....nothing about the Koloko dam!


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