Gg 101

GG 101 Sample Field Trip Report Nuuanu Stream Observations I live in Nuuanu in a small cottage behind another home just off the Pali Highway on the Diamond Head side, not far from where the Old Pali Road begins and close to upper Dowsett Ave. A small stream runs behind the cottage, at it';s closest it comes to within six feet of the cottage, needless to say we have become accustomed to the constant sound of running water, we are very fung shui! After doing a little research I learned that the stream is probably a part of an ancient ‚Äúauwai‚Äù system built by Hawaiians in the 1800';s to provide water for taro cultivation. Nuuanu was a primary food growing area for Hawaiians on Oahu and contained many terraced taro fields. The stream';s head originates from an offshoot of the larger Nuuanu Stream above Dowsett Ave. and the mouth empties into lower Nuuanu Stream. From my back lanai I can observe approximately 50 feet of stream. The following are my observations: We can observe approximately 20 feet upstream and 30 feet downstream from a point behind our house. The stream is fairly straight along this section but you can see that it bends both upstream and downstream. At this point the stream channel during ‚Äúaverage‚Äù rainfall periods is approximately 3 feet across at the base, 12 feet across at the top of the channel and 7 feet deep, the water depth at the base is approximately 1 ¬O feet deep. The sides of the channel are or used to be man-made lava rock walls, the rocks in the wall appear to be cemented together. Velocity: Due to the narrow channel the water flow is quite rapid, there are some small areas where the water deepens and is calmer, ducks like these areas. I';m not sure of what the estimated number of feet per second that the water is moving. The stream bed has large rocks and in some cases boulders as well as a good deal of vegetation which acts to slow down the water flow, which in turn, create the calm pond like areas that the ducks enjoy. I estimate the gradient of the stream somewhere between ¬O in. to 1 in. drop per foot, a fairly steep slope but when I compare it with the elevation change of the Pali Highway through the valley it is reasonable that it should be quite steep. The velocity and discharge of the stream are naturally greatly impacted by rainfall. My husband and I have spent two winters in Nuuanu with the last being exceptionally

wet. I believe it was the same weekend as the Manoa flood last October. It started raining heavily in the afternoon, virtually a constant downpour and we could see it was raining very heavy up in the valley above us, we observed that within a two hour period the stream volume swelled from it';s usual 1 ¬O ft. depth and 3 ft. width to more than 6 ft. deep and 12 feet wide. This volume lasted approximately two hours. During this time the narrow channel restricted the flow of water causing it to back up and spill over the banks resulting in flooding of property on the lower banks, fortunately for us this was the bank on the opposite side of the stream from us, but not so fortunate for the elderly lady living in the house across the stream from us, the basement of her house flooded. Erosion: The stream demonstrates a number of erosional characteristics. The banks are eroding and the stream is undercutting the wall. There are visible sections of wall that have collapsed or eroded leaving rocky banks. Right below our house is a large chunk of the rock wall that has obviously been eroded and dislodged; it now lies in the middle of the stream channel. There is also a very large boulder, approximately 6 ft. in diameter, in the channel, this boulder must have dislodged from one of the sides or has been transported from further up the stream. This boulder and wall remnants create a dam across the stream resulting in the small pond area that the ducks enjoy. The top of this boulder is usually well above the water line and in fact there are small plants growing on the top of it, but during the aforementioned flooding the boulder was completely under water. The boulders and rocks do not show a great deal of signs of weathering, they do not seem to be rounded or very worn down, I am inclined to suspect that the type of rock do not easily wear down in this manner, it looks like this rock material may crack and crumble instead of rounding off the edges. Pollution: I feel compelled to comment that the water quality does not appear to be very good; I have observed that sometimes the water has a milky appearance. I';m sure that drainage run-off from yards and gardens along the banks contributes to a fair amount of fertilizers, chemicals and animal waste in the water. Unfortunately, I';ve also occasionally noticed litter or refuse, such as a plastic tofu container along the banks. We attempt to keep it clean but access is difficult.