Laserfiche WebLink
<br />(al temporary damming of the channel by a large landslide, such <br />as the landslide exposed in a roadcut in the Big Narrows, and (b) <br />an intense rainfall, similar to the storm responsible for the <br />1976 flood in Big Thompson Canyon. <br /> <br />The next component of this research is therefore to evaluate <br />potential sources of the floodwaters recorded in lower Poudre <br />Canyon. The debris-flow-dam scenario can be evaluated by <br />reconstructing the extent of the water ponded behind the Big <br />Narrows dam, and then routing this water downstream using a model <br />like the National Weather service's DAMBREAK. We will also <br />attempt to further constrain this scenario by obtaining <br />radiocarbon ages for the debris flow deposits, and comparing <br />these to the ages of the flood deposits. The rainfall scenario <br />can be evaluated through the use of a rainfall-runoff-discharge <br />model, such as the Army Corps of Enginee~s' HEC-l. We will model <br />the flows produced by rainfalls of differing intensities and <br />locations, using systematic precipitation data to realistically <br />constrain potential rainfalls. Each of these flood scenarios <br />will probably form the topic for a Master of Science thesis by a <br />student in the Department of Earth Resources at Colorado state <br />University. <br /> <br />In addition, future work on this project will address the <br />objectives outlined initially in this report; the relation of <br />prehistoric floods to past climate, and the enhancement of flood- <br />frequency predictions in the Poudre basin. The latter can be <br />accomplished using recently-developed statistical programs based <br />on maximum-likelihood estimators, which permit systematic and <br />geologic data to be combined in flood-frequency analysis. These <br />objectives require a more complete flood chronology, however, and <br />we are currently seeking further funds for radiocarbon dates. <br /> <br />VII. REFERENCES CITED <br /> <br />Jarrett, R.D. 1989. Hydrology and paleohydrology used to improve <br />the understanding of flood hydrometeorology in Colorado. In, M.C. <br />Albertson and R.A. Kia, eds., Design of hydraulic structures 89, <br />A.A. Balkema, Rotterdam, p. 9-16. <br />