Thesis (doctoral)--Wageningen University, 2006. / Vita. "Propositions" ([1] leaf) inserted. Includes bibliographical references.

Excess sedimentation began affecting the wetland dynamics of Pine Gully in Seabrook, Texas during the first quarter of 2004. This sedimentation was sudden and became a serious problem for the dynamics of the Pine Gully wetland because the fine, well sorted, quartz rich sediments began plugging the main channel of the previously tidally dominated wetland. Progressive sedimentation has produced overbank deposits in the marine grasses, contributing to the death of wetland grasses by sediment chocking. The main purpose of this study is to determine the new source and mechanism of sedimentation in Pine Gully, document changes from sedimentation, and determine a solution to prevent future sedimentation. Sedimentation in Pine Gully and coastal areas adjacent to Pine Gully has occurred in a region that has experienced subsidence and sea level rise. The sedimentation in Pine Gully is a direct result of new and sustained sediment at the mouth of Pine Gully. These new sediments are transported into Pine Gully by displacement waves from ships moving through the Houston Ship Channel. Beach renourishment at Wright Beach, located a half mile north of Pine Gully, occurred as Pine Gully experienced sedimentation. Construction of a breakwater at the mouth of Pine Gully and subsequent removal of sediment in Pine Gully itself is ultimately the solution to revitalizing the wetland to its pre-sedimentation state. Replanting of native vegetation killed off by sedimentation is recommended and would hasten the recovery of the wetland. Documenting the effects of this unique sedimentation in Pine Gully has implications for the future. Beach renourishment or coastal projects that may contribute excess sediment to the coastline should be concerned with unintended effects they may cause. Although an historically eroding shoreline exists, the effects of excess sedimentation can be severe. A coastal study should be done before sediment is added to the shoreline to identify any areas within the sphere of influence of the project. Ecosystems determined to be within the sphere of influence by a coastal study should implement preventative measures at those locations to avoid an ecological disaster similar to that in Pine Gully.

One of the environmental problems today in seas, lakes and streams is eutrophication. This is often caused by nutrients such as phosphorus (P) and nitrogen (N) that leak from agricultural areas. A measure to partly prevent the nutrient discharge is to construct or restore wetlands. In order to control the efficiency of nutrient reduction of existing wetlands in the county, the administrative board in Västra Götaland wants to find different criterias for reference wetlands. These reference wetlands should represent other wetlands and be used in future evaluations of reduction of nutrients and design of constructed wetlands. According to the administrative board in Västra Götaland the reference wetlands should have a catchment area of about 50 hectare consisting of at least 70 % arable land, to represent wetlands created to remove nutrients. The surface area should exceed 0,5 hectare and the inlet-nitrogen concentration should be around 5 mg N-1. This report investigates nitrogen and phosphorus retention in two wetlands, Härstad and Åmot in the county of Västra Götaland, and if they fulfill the criteria of being a reference wetlands. In addition to this, a tracer study was performed in one of these wetlands with the purpose to study the hydraulic efficency. Neither the wetland in Åmot or Härstad achieves the guidelines of about 5 mg N l-1 in the incoming water. Therefore, they can be seen as inappropriate as reference wetlands according to their nitrogen retention. The wetland of Härstad, however, has significantly better N retention than the wetland of Åmot. Results from the report shows that N retention in the wetland of Härstad was relatively high not only due a higher N load, but also due to that N was largely in the form of NO3- facilitating efficient transformation of NO3- to N2 by denitrification bacteria. Nitrogen removal was much lower in the wetland in Åmot due to that N in incoming water was not in the form of NO3- and could therefore not be efficiently transformed to N2 by denitrification. Incoming total phosphorus to the Härstad and Åmot wetlands exceeded 100 µg P l-1, which means "extremely high" tot-P concentrations according to environmental quality criteria from the Swedish Environment Protection Agency. Phosphorus load per wetland area was slightly higher in the wetland in Åmot than in the Härstad wetland. In spite of this, P retention per wetland area as well as relative P retention was clearly higher in the Härstad wetland. This can be explained by that P in incoming water to the Härstad wetland was to a larger degree than in the Åmot wetland bound to particles, facilitating P retention through sedimentation. According to the tracer study, the Härstad wetland has a hydraulic efficency (λ) of about 0,13 which means it has a low hydraulic efficiency. The effective volume ratio (e) in Härstad was calculated to 18 % which means that the water has an inadequate spreading in the wetland, which is not good for the nutrient elimination in this wetland. This study illustrates the difficulties in finding representative reference wetlands due to potential differences between wetlands in nutrient concentrations in incoming water, the degree that incoming P is bound to particles, the degree that incoming N is in the form of NO3-, and hydraulic efficiency.

Excess sedimentation began affecting the wetland dynamics of Pine Gully in Seabrook, Texas during the first quarter of 2004. This sedimentation was sudden and became a serious problem for the dynamics of the Pine Gully wetland because the fine, well sorted, quartz rich sediments began plugging the main channel of the previously tidally dominated wetland. Progressive sedimentation has produced overbank deposits in the marine grasses, contributing to the death of wetland grasses by sediment chocking. The main purpose of this study is to determine the new source and mechanism of sedimentation in Pine Gully, document changes from sedimentation, and determine a solution to prevent future sedimentation. Sedimentation in Pine Gully and coastal areas adjacent to Pine Gully has occurred in a region that has experienced subsidence and sea level rise. The sedimentation in Pine Gully is a direct result of new and sustained sediment at the mouth of Pine Gully. These new sediments are transported into Pine Gully by displacement waves from ships moving through the Houston Ship Channel. Beach renourishment at Wright Beach, located a half mile north of Pine Gully, occurred as Pine Gully experienced sedimentation. Construction of a breakwater at the mouth of Pine Gully and subsequent removal of sediment in Pine Gully itself is ultimately the solution to revitalizing the wetland to its pre-sedimentation state. Replanting of native vegetation killed off by sedimentation is recommended and would hasten the recovery of the wetland. Documenting the effects of this unique sedimentation in Pine Gully has implications for the future. Beach renourishment or coastal projects that may contribute excess sediment to the coastline should be concerned with unintended effects they may cause. Although an historically eroding shoreline exists, the effects of excess sedimentation can be severe. A coastal study should be done before sediment is added to the shoreline to identify any areas within the sphere of influence of the project. Ecosystems determined to be within the sphere of influence by a coastal study should implement preventative measures at those locations to avoid an ecological disaster similar to that in Pine Gully.

Constructed wetland system is a natural purifying procedure of management and disposal of water and wastewater by means of Ecological Engineering Technology. Neither additional chemical agent nor mechanical equipments and electrical power are needed in the procedure of water quality purifying. It is also a potential Ecological Engineering Technology with advantages of low-cost, easy operation and management, and easy construction. However, the limitation of this technology is the requirement of larger land space for wetland construction. Taiwan features in a subtropical climate, moderate water temperature, abundant sunlight, so its environmental condition is a good fit for constructed wetland technology, which has been verified by numerous pilot and field scales studies in recent years. Due to the necessity of large land space, it is impossible to apply it in the urban environment that is densely populated. In the rural area of Taiwan, however, with the industry development or industry moving outside, there appears a lot of fallow lands, idle lying factories. Moreover, the undeveloped construction of sewage work in Taiwan (especially in rural areas) results from inadequate construction expenditure supported by government, while discharge raw sewage in urban causes water pollution and water shortage. Hence, if we could establish constructed wetlands in the programmed proper places (such as presumptive address in parks or low-rent fallow lands), less construction expenditure could be used to construct sewage work and to protect water resource. After the proper programming and management, constructed wetland has multiple functions such as sightseeing, recreation, and ecology education. In order to explore the possibility of domestic wastewater disposal by constructed wetlands, the research adopted three ecological engineering treatment systems: Erhang constructed wetland system, Gangwei constructed wetland system, and Dajia soil filtration system. In this study, the treatment efficiencies and effectiveness of water quality improvement via these three systems were investigated. Results from the monitoring results of the influents and effluents of these systems were evaluated. In the Erhang constructed wetland, results were collected from July 2004 to October 2005. During this investigation period, the average flow rate was 52 CMD, and the observed biochemical oxygen demand (BOD) removal efficiency and removal rate were 72¡Ó22¢H and 1.68¡Ó1.12 kg/day, respectively. In the Gangwei constructed wetland, results were collected from July 2004 to May 2006. During this investigation period, the average flow rate was 61.6 CMD, and the observed BOD removal efficiency and removal rate were 33¡Ó40¢H and 0.14¡Ó0.19 kg/day, respectively. In the Dajia constructed wetland, results were collected from July 2004 to May 2006. During this investigation period, the average flow rate was 21.92 CMD, and the observed BOD removal efficiency and removal rate were 79¡Ó16¢H and 0.9¡Ó0.5 kg/day, respectively. Results from this study indicate that the three systems could effectively remove the main pollutants in inflow water and the treated water is able to meet the discharged standards. Thus, the constructed wetland scheme has the potential to be developed into an environmentally and economically acceptable domestic wastewater treatment technology. Results from this study will be useful to assist environmental professionals in designing a scale-up system for future application.

In north central Texas, USA, free-water surface wetlands have been constructed to treat pre-treated wastewater effluent from the Trinity River. Water quality and vegetation data from the first two years of operation (June 2003 to May 2005) were used to determine cell-to-cell and system-wide removal efficiency of total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN). The wetland system consisted of one non-vegetated sedimentation basin and a series of four connected, vegetated wetland cells. Temporal analyses displayed varying monthly, seasonal and yearly trends of the wetlands’ concentration of the three parameters. Spatial analysis results confirmed that TSS, TP and TN concentrations were greater at the beginning of the system as compared to the end of the wetland system. Percent reduction analyses showed that the second wetland cell (WC2) was the most efficient in TSS, TP and TN removal, while the last wetland cell (WC4) had the lowest reduction of the three parameters. TSS removal was significant (α = 0.05) moving consecutively among the sites in the wetland system, with exception to the last wetland cell. TP removal was only significant (α = 0.05) moving from the third wetland cell (WC3) to WC4, while TN removal was significant (α = 0.05) moving from the sedimentation basin to the first wetland cell (WC1) and then again moving from WC3 to WC4. Overall removal efficiency of the wetland system (from the Trinity River to WC4) was quite high, with reductions over 97% for TSS, 47% for TP and 67% for TN. N:P ratios decreased moving consecutively throughout the field-scale wetlands. Vegetation analyses found WCs 1 and 3 to contain the greatest vegetation species richness, while WC2 had the lowest richness. The vegetative composition of the four cells was mostly the same. A comparison was conducted between the nutrient reduction efficiency and vegetation data of this wetland system with data from a pilotscale wetland system that was operated from 1992 to 2000. The findings of this study suggest that during the first two years of operation, the wetland system’s performance is comparable to the pilot-scale wetlands which were operated for eight years.

The purpose of this study was to identify and quantify estuarine and marine wetland and shore changes circa Galveston Bay Estuary (GBE) from 1995 to 2002 by using aerial photography and GIS mapping techniques. Aerial photographs in digital format were acquired from Texas Natural Resource Information System (TNRIS) and the Houston Galveston Area Council (HGAC); these photographs were selected because the images were taken at the time period desired, existed in digital formats at resolutions of 1 m or greater, and were in coordinate systems that were already in or could be properly aligned and georeferenced. Maps for each of thirty quadrangles that include estuarine and/or marine habitats around the GBE were created, depicting wetlands and shorelines for the years 1995 and 2002 as well as changes between the two time periods. Polygons representing different habitats in 1995 were drawn while working at a scale of 1:4,000 or greater. Maps of habitats in 2002 and maps showing changes from 1995 to 2002 were produced by modifying individual 1995 polygons to document boundary shifts or habitat changes from 1995 to 2002. All resulting maps were constructed at 1:24,000 scale in UTM NAD 83 coordinate system to match USGS quad maps. Areas of each habitat in 1995 and 2002 and changes between the two years were calculated in acres and comparisons were made. There were four objectives developed to be examined by the creation of the new set of maps for GBE. They were to determine habitat changes during the time period in question, effectiveness of mapping technique, where differences in change occurred, and what type (i.e. erosion, development, accretion, etc.) of change occurred. My analyses of these maps indicated that there were 117,670 acres of estuarine wetlands and 21,983 acres of unconsolidated estuarine and marine shores present in 1995. In 2002, these values changed to 116,534 acres of estuarine wetlands and 21,630 acres of estuarine and marine shores. The rate of wetland loss was estimated as 162 acres per year or 0.1% of all wetlands annually from 1995 to 2002. This rate has slowed from the previous rate of 405 acres per year or 0.4% in 1979 and remained the same as the 161 acres per year or 0.1% reported in 1993 for the GBE. Further, the results of my analyses indicated that losses from direct human influences (e.g. development, dredging, and filling) were less than losses associated with natural processes like erosion and subsidence.

Thesis (Ph. D.)--University of Washington, 2002. / Includes bibliographical references (p. 101-114).

Thesis (M.Sc.(Botany))--University of Pretoria, 2004. / Includes summary. Includes bibliographical references (leaves 162-169).

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xii, 99 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 80-83).