Types of Channel Modifications of Hawaiian Streams
Timbol and Maciolek (1978) distinguished six types of channel modifications of streams in the Hawaiian Islands.
1. Lined channel. An artificial channel having both natural banks and stream bed replaced, usually with concrete. It may be flat bottom or v-shaped. Representative examples are in Palolo tributary of Manoa stream (leeward Oahu) and Ahuimanu tributary of Kahaluu Stream (windward Oahu).
2. Vegetation removed-channel realigned.
Represented by Kapalama Stream.
3. Elevation culvert. These are conduit structures that are comparatively short (typically <60 m), usually found under highways. Culverts placed in this category include only those where the culvert level is well above the water level immediately downstream, i.e., the culvert creates an artificial waterfall. An example of an elevated culvert is in Aolani tributary of Kaneohe Stream (windward Oahu).
4. Revetment. Where one or both banks of the stream are reinforced but the channel bed is not, as in Kalihi Stream (leeward Oahu).
5. Blocked or filled-in channel. Where part of the original
channel is blocked as in Pauoa tributary of Nuuanu Stream
6. Extended culvert. This is a longer version of the modification type 3, usually found in residential areas as in Kawa Stream in Kaneohe (windward Oahu).
According to Timbol and Maciolek (1978), older examples of stream channel modifications in Hawaii are the result of bridge building. The oldest forms of channel modification are clearing-realignment and revetments to reinforce stream banks. Most of these types of modifications on Oahu Island were done in the 1930 - 1950 period. The most significant form of modification ecologically and numerically is the lined channel, the earliest of which was built in 1938 at Kapalama Stream (Honolulu, Oahu). Lined channels represent a majority of recently built flood-control structures.
Survey Data by Island