Geomorphic History of the Grand River and Grand River Valley: Natural and Anthropomorphic Hydraulic Controls

Preliminary investigation into the feasibility and benefits of removing 5 low head dams located on the Grand River, in the city of Grand Rapids, Michigan, is currently underway. The anthropomorphic hydraulic controls (dams), constructed in the late 1800’s, were built at the location of several bedrock exposures which served as natural hydraulic controls. Prior to dam construction, an abrupt change in river gradient at these exposures resulted in the rapids for which Grand Rapids is named. Evaluation of several alternatives for restoring more natural flow and sediment dynamics in the Grand Rapids reach is part of the removal effort. This study provides a detailed explanation of the geomorphic setting and history of the entire Grand River, including new mapping and sediment data for five natural hydraulic controls that were identified during preliminary investigation of the region. These controls were confirmed through bathymetric mapping of a ~13 kilometer reach upstream of Grand Rapids between Ada and Lowell, Michigan. A 135 meter long and roughly 30 meter wide exposure of boulder-rich fluvial sediment was identified 5 kilometers upstream of Ada, Michigan. The exposure trends generally N-S and contains fine sand to large boulders. The surface of the exposure possesses a D50 of 87.6 mm and a D10 and D90 of and 12.2 mm and 1,302 mm, respectively. The subsurface of this deposit has a D50 of 14.8 mm and a D10 and D90 of 7.3 mm and 95.5 mm, respectively. The top of the deposit is not flat. Surveying indicates the elevation of the top of the deposit varies by up to a meter. This exposure provides unique substrate and habitat uncommon in the Grand River, which is primarily a sand and silt dominated river. Further mapping and sampling of this exposure may provide data which will allow this reach to be used as an analogue for restoration efforts in Grand Rapids. The Grand River Valley (GRV), through which the lower Grand River flows, is significantly larger than the modern floodplain. Previous research has suggested that the GRV was formed, since the last glacial maximum (LGM), by glacial outwash travelling from the Huron Basin to Glacial Lake Chicago (in the Lake Michigan Basin). Mapping and analysis of approximately 40,000 water wells adjacent to the Grand River Valley revealed: 1) a bedrock channel, presumably occupied by the ancestral Grand River; 2) evidence for a Grand River outlet north of the modern location which predates the LGM; and 3) a N-S trending area of thick alluvium and boulder occurrence which may represent valley fill of the pre-LGM bedrock valley

The status of GEO 600

The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode

Upper limits on the strength of periodic gravitational waves from PSR J1939+2134

The first science run of the LIGO and GEO gravitational wave detectors presented the opportunity to test methods of searching for gravitational waves from known pulsars. Here we present new direct upper limits on the strength of waves from the pulsar PSR J1939+2134 using two independent analysis methods, one in the frequency domain using frequentist statistics and one in the time domain using Bayesian inference. Both methods show that the strain amplitude at Earth from this pulsar is less than a few times $10^{-22}$.Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July 200

Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers

We study frequency dependent (FD) input-output schemes for signal-recycling interferometers, the baseline design of Advanced LIGO and the current configuration of GEO 600. Complementary to a recent proposal by Harms et al. to use FD input squeezing and ordinary homodyne detection, we explore a scheme which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are sub-optimal among all possible input-output schemes, provide a global noise suppression by the power squeeze factor, while being realizable by using detuned Fabry-Perot cavities as input/output filters. At high frequencies, the two schemes are shown to be equivalent, while at low frequencies our scheme gives better performance than that of Harms et al., and is nearly fully optimal. We then study the sensitivity improvement achievable by these schemes in Advanced LIGO era (with 30-m filter cavities and current estimates of filter-mirror losses and thermal noise), for neutron star binary inspirals, and for narrowband GW sources such as low-mass X-ray binaries and known radio pulsars. Optical losses are shown to be a major obstacle for the actual implementation of these techniques in Advanced LIGO. On time scales of third-generation interferometers, like EURO/LIGO-III (~2012), with kilometer-scale filter cavities, a signal-recycling interferometer with the FD readout scheme explored in this paper can have performances comparable to existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi