Browsing by Subject "Runoff"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Impacts of unpaved roads on runoff and sediment production in Culebra, Puerto Rico(2019-12) Mclaughlin, Preston Wyatt; Ramos-Scharrón, Carlos E.Terrigenous sediment delivery into tropical coastal waters from unpaved road development is a key stressor influencing the global decline of coral reef ecosystems. Higher turbidity of coastal waters from this terrigenous sediment can result in smothering, bleaching, and reduced photosynthetic activity for coral reefs. Since the 1990’s, the small Puerto Rican municipality of Culebra has experienced significant rates of land development, and an expansion of its unpaved road network, which has been identified as the contributing factor responsible for the continuous decline of the island’s live coral cover. This research focuses on quantifying runoff, and sediment production rates for Culebra’s unpaved road and undisturbed surfaces at the plot (~3 m²), and watershed (~1 km²) scales. A total of 46 rainfall-runoff simulations, and 119 Guelph permeamter tests were conducted to collect this data. Results indicate that only 1.2 mm of rainfall is required to produce overland flow on unpaved roads. At least 7.9 cm of rainfall is needed to generate overland runoff on undisturbed hillslopes. Erosion rates were greatest for recently graded road segments, with an average annual erosion rate of 54.65 Mg ha⁻¹ yr⁻¹. Unpaved roads that have been left ungraded for over one year erode at about half this rate (29 Mg ha⁻¹ yr⁻¹). Undisturbed surface erosion was negligible in comparison, with a mean rate of 0.05 Mg ha⁻¹ yr⁻¹. Based on this data, there are up to five orders of magnitude difference between erosion rates of graded unpaved roads and natural soil surfaces in Culebra. Within one year, a total of 335 storms occurred between. Around a quarter of all recorded storms produced overland runoff on unpaved road surfaces. Hurricane Maria was estimated to be the only storm that year to generate overland flow on undisturbed surfaces. ArcGIS was used to identify segments of road most likely to transport overland runoff to the coastline, as well as segments generating the most erosion. Sediment production rates for the study areas ranged between 3.1 and 10.9 Mg yr⁻¹. This information is beneficial towards documenting the overall effectiveness of erosion mitigation structures built to reduce terrigenous sediment transport produced from these roadsItem A Mexican case study for world water online(2012-05) Espinoza Dávalos, Gonzalo Enrique; Maidment, David R.; McKinney, Daene C.World Water Online is a global system of hydrologic data. It is an integration of geospatial and temporal information across spatial scales: global, national, regional and local. This global water information system has no parallel, and its scope would be extended with the active participation of the global water community. Its consolidation depends on the accessibility of countries’ databases through the system. In this study, a test case using Mexican data within World Water Online is created, applying the CUAHSI framework, web services and standards. The resulting Mexican-HIS unifies the water information for the nation regardless of data provider, improving storage practices and allowing additional querying and retrieving functionalities: World Water Online is a source of information and also a supplier of web-based processing services. In the second part of this study, a precipitation-runoff analysis using the data in the system is performed.Item Reducing turbidity of construction site runoff via coagulation with polyacrylamide and chitosan(2012-05) Rounce, David Robert; Lawler, Desmond F.; Barrett, Michael E.The U.S. Environmental Protection Agency is in the process of developing a nationwide standard for turbidity in construction site runoff. It is widely expected that this standard cannot be met with conventional erosion and sediment control measures; consequently, innovative practices for managing sediment on construction sites must be developed. The objective of this research was to develop an understanding of how soil characteristics and polymer properties affect the amount of turbidity reduction that can be achieved through flocculation. The polymers used were PAMs, a proprietary product, and chitosan. The charge density of the PAMs ranged from 0% to 50% and the molecular weights ranged from 0.2 to 14 Mg/mol. A protocol for creating modified synthetic stormwater runoff for soil samples was developed and used on soils from seven construction sites. Particle size distributions were used to compare the modified synthetic stormwater runoff with grab samples of stormwater from one site and showed the synthetic runoff was representative of the actual runoff. Flocculation tests were performed on the synthetic runoffs with PAM and chitosan doses from 0.03 to 10 mg/L. The non-ionic PAM, proprietary product, and chitosan were found to be the most effective at reducing the turbidity of all the synthetic runoff below 200 NTU. The high molecular weight anionic PAMs were effective on only two of the seven synthetic runoff samples. Hardness tests were performed indicating interparticle bridging to be the bonding mechanism of the PAM. Electrophoretic mobility tests were performed on two of the soil suspensions and indicated the bonding mechanism of PAM to be interparticle bridging, and the bonding mechanism of chitosan to be a combination of charge neutralization and interparticle bridging. Tests showed as the charge density of the PAM increased, their effectiveness decreased.