Thesis supervisor: Jerald L. Schnoor. Thesis supervisor: Craig L. Just. Includes bibliographic references (p. 186-196).

Rivers in the U.S. Midwest are dynamic systems that can be natural laboratories for understanding the different modes of bank erosion, namely fluvial erosion, mass erosion, and mass failure. Fluvial and mass erosion are hydraulically driven and semicontinuous, whereas mass failure is episodic and often catastrophic. Being catastrophic, mass failure and its driving mechanisms have received considerable attention comparatively to mass and fluvial erosion. However, the linkage between hydraulically driven erosion and mass failure has not been examined fully. We hypothesize that fluvial and mass erosion affect the memory and response of the system by creating favorable hydrogeomorphic conditions for mass failure. This dissertation addresses three major shortcomings in the bank erosion literature, including the confusion surrounding critical erosional strength values for mass and fluvial erosion (τc,m and τc,f, respectively). The herein results clearly show that these two parameters are different, with τc,m being three to five times greater than τc,m. Therefore, excluding mass erosion estimates from sediment budgets or stability analyses can lead to significant errors in quantifying or predicting bank retreat and channel geometry. In addition, this study offered a methodological improvement for measuring the τc,m in-situ using Photo-Electric Erosion Pins, which semi-automatically measure mass erosion to generate erosional strength and erodibility values that are currently missing in the literature. This study also addressed the preconceived notion in morphodynamic modeling that bank soil profiles are homogeneous and universal strength/ cohesion parameters adequately represent the bank soil profile. This study shows that bank soil heterogeneity is present and significantly affects bank stability. Therefore, heterogeneity along a bank face must be assessed in at least three locations to provide adequate input data for bank erosion models. Finally, this study suggests that Factors of Safety for mass failure must be complemented with those for fluvial and mass erosion to avoid underestimating mass failure by as much as 30%. Hence, this study provides agencies like the U.S. Department of Agriculture key data regarding the total contributions from the different modes of bank erosion and channel, itself, to the stream sediment load for strategic targeting of Best Management Practices and in-streams stabilization structures.

This document presents a sketch of the engineering and legal considerations necessary to implement a distributed storage flood mitigation system in Iowa. This document first presents the results of a simulation done to assess the advantages of active storage reservoirs over passive reservoirs for flood mitigation. Next, this paper considers how forecasts improve the operation of a single reservoir in preventing floods. After demonstrating the effectiveness of accurate forecasts on a single active storage reservoir, this thesis moves on to a discussion of distributed storage with the idea that the advantages of active reservoirs with accurate forecasting could be applied to the distributed storage system. The analysis of distributed storage begins with a determination of suitable locations for reservoirs in the Clear Creek Watershed, near Coralville, Iowa, using two separate algorithms. The first algorithm selected the reservoirs based on the highest average reservoir depth, while the second located reservoirs based on maximizing the storage in two specific travel bands within the watershed. This paper also discusses the results of a land cover analysis on the reservoirs, determining that, based on the land cover inundated, several reservoirs would cause too much damage to be practical. The ultimate goal of a distributed storage system is to use the reservoirs to protect an urban area from significant flood damage. For this thesis, the Clear Creek data were extrapolated to the Cedar River basin with the intention to evaluate the feasibility and gain a rough approximation of the requirements for a distributed storage system to protect Cedar Rapids. Discussion then centered on an approximation of the distributed storage system that could have prevented the catastrophic Flood of 2008 in Cedar Rapids. There is significant potential for a distributed storage system to be a cost effective way of protecting Cedar Rapids from future flooding on the scale of the Flood of 2008. However, more analysis is needed to more accurately determine the costs and benefits of a distributed storage system in the Cedar River basin. This paper also recommends that a large scale distributed storage system should be controlled by an entity be created within the Iowa Department of Natural Resources. A smaller distributed storage system could be managed by a soil and water conservation subdistrict. Iowa allows for condemnation of the land needed for the gate structures and the flowage easements necessary to build and operate a distributed storage system. Finally, this paper discusses the environmental law concerns with a distributed storage system, particularly the Clean Water Act requirement for a National Pollutant Discharge Elimination System permit.

Data on the life cycle of Hydropezrla crosbvi were collected from January, 1974, to March, 1976, in Clear Creek, Denton County, Texas. Laboratory investigation helped in establishing instar number, egg incubation and description, and first instar descriptions. Adult Hydroperla crosbyi emerge in February - March when water temperature increases to a mean of 15 C. Eggs undergo a diapause, hatching when decreasing water temperature reaches 18 C in October - November. Maximum growth occurs when water temperatures are coldest. Male and female nymphs undergo ca. 12 and 14 instars, respectively. Larvae of Simuliidae and Chironomidae are the preferred food items of nymphs throughout the growth season.

Thesis (D. Min.)--Western Seminary, Portland, OR, 2010. / Abstract. Includes bibliographical references (leaves 164-165).