Autumn Floods Research Articles

Spillway design floods In Sweden: II. Applications and sensitivity analysis

Abstract The recently developed guidelines for design flood calculation in Sweden are based on simulation with a hydrological model. Several meteorological and hydrological conditions are prescribed as input to the model. The sensitivity of the floods according to the new guidelines with respect to those prescriptions is checked as well as the sensitivity to the modelling procedure. In this paper, the HBV hydrological model is used. It is shown that the most sensitive input factor is the design 14-day precipitation sequence. For autumn floods, the scaling relation between the precipitation sequence and the generated floods is in the order of 1:1. For spring floods on the other hand, snowmelt influences the flood magnitude and reduces the sensitivity to precipitation to about 1:0.6. Soil moisture modelling was important in basins with high evapotranspiration. Model calibration could have a large effect on the design flood magnitude. The most sensitive parameter was the high flow recession coefficient, K0 ....

The Shu Zhuang School

Among all the post-Zhuang Zi schools of Zhuang Zi philosophy, the Shu Zhuang school was the school of most direct descent. Its works included the twelve "chapters": "Qiushui" (Autumnal floods), "Zhi le" (Utter happiness), "Da sheng" (Arriving at life), "Shan mu" (The forest in the mountain), "Tian Zifang," "Zhi beiyou," "Geng Sang Chu," "Xu wugui," "Ze yang," "Wai wu" (External things), "Yuyan" (Fable), and "Lie Yukou." From the intellectual content and linguistic style of these essays, the works of the Shu Zhuang school appear to belong to a chronologically earlier category of the outer and miscellaneous chapters. The chief characteristic of this category of writings is that they inherited and basically developed the meaning of the ideas of the "inner chapters." They provided a more careful and detailed explanation of Zhuang Zi's theories of original source (bengen), true knowledge (zhenzhi), and the equality of things (qi wu), and they also developed other key ideas of Zhuang Zi, including his idea of human life. The Shu Zhuang school did, to a certain extent, reform and develop Zhuang Zi's ideas, but there is no major breakthrough (or breaking away) from his ideas, and, basically, the work of this school was to elaborate but not to innovate. The works of the Shu Zhuang school served as the major corpus of reference material for the study of Zhuang Zi's ideas. In Part 2 of this book, where we developed an interpretaion of Zhuang Zi's ideas, we have already touched on some of these essays written by the people of the Shu Zhuang school. Let us now analyze and critique the ideas of this school in a more concentrated fashion.

Effects of waterlogging on the growth and water relations of three Pinus taxa

The response of Caribbean pine ( Pinus caribaea Morelet. var. hondurensis Barr. and Golf.), slash pine ( Pinus elliottii Englem. var. elliottii) and their F 1 hybrid to soil waterlogging was studied under glasshouse conditions. Plants were grown in either a lateritic or gleyed podzolic soil and pots were flooded in both autumn and summer treatments. Plant responses were influenced by both season and duration of flooding, and by soil type. All the Caribbean pine seedlings survived the autumn flooding, but showed very slow growth and had very low needle conductances. Summer-flooded plants exhibited rapid stomatal closure and low needle water-potentials accompanied by needle dehydration. All of the summer-flooded Caribbean pine seedlings died. Slash pine was much more flood-tolerant than was Caribbean pine, whilst the F 1 hybrid was intermediate between the two parents. All slash pine and F 1 hybrid seedlings survived autumn flooding and continued to grow, but survival was reduced with summer flooding, particularly in the short-term flooding treatment. Slash pine and F 1 hybrid seedlings showed morphological features of flood tolerance with production of adventitious roots and formation of lenticels in association with stem hypertrophy. Although stomatal opening was evident during autumn flooding, needle conductance was very much reduced in summer-flooded plants of these two taxa. Needle water-potential and relative water content were maintained near the control value in flooded slash pine grown in both soil types, but only for the F 1 hybrid in the flooded lateritic podzolic soil.

Proposed Swedish Spillway Design Guidelines Compared with Historical Flood Marks at Lake Siljan

A comparison between the proposed Swedish spillway design floods and historic flood marks made at lake Siljan in central Sweden, is shown. Frequency analysis is performed incorporating pregauge information on water levels together with a sensitivity analysis of modelling assumptions. A water level of 0.42 to 0.75 metres above the highest historic flood mark (166.10 m.a.sl., 1659) was obtained when routing the design spring flood through lake Siljan. The design autumn flood lifted the lake to 1.56 to 1.52 metres below the highest flood mark. Return period for the design spring and autumn flood was estimated to about 1,000 years. The uncertainty in frequency analysis proved to have larger impact than modelling assumptions on estimating the risk of the design flood.

Effect of Stocking Density on the Survival, Growth, and Dispersal of Steelhead Trout Fry (Salmo gairdneri)

In a coastal British Columbia stream a stocking density of between 0.3 and 0.7 fry/m2 maximized the production of steelhead trout (Salmo gairdneri) parr and smolts. A severe autumn flood doubled the mortality rates of fry stocked at densities of 0.7 fry/m2 or higher but had little effect on fry stocked at lower densities (<0.15 fry/m2). Overall survival to smolts appeared to be lower than measured elsewhere for wild fish (2 vs. 4.5 – 18%). The proportion (<10%) of surviving fry found below the stocked sections was considered to be an indicator of potential displacement mortality in streams with no vacant downstream areas. This downstream dispersal was not density dependent and was small in comparison with the mortality of nondispersing fish. Although initial fry and parr sizes were density dependent, there was no detectable density effect on older parr or smolt sizes.