No description available.

Tropical regions have extensive networks of unpaved roads which can be the largest contributor of sediment loading within a watershed in terms of both sediment generation and delivery. A number of erosion and sediment prediction models have been developed for unpaved roads and applied across a wide range of locations. However, little work has been devoted to the comparison of these models or to their application in tropical environments. A 13 square kilometer mixed land use watershed in Eastern Brazil was used as a case study area for model application and comparison. Models chosen for evaluation were WEPP: Road, SEDMODL, and STJ-EROS. To determine the applicability of these models to the case study watershed, a classification system was developed to score road segments according to sediment production and delivery potential. Field observations provided data for the input parameters of the models as well as to identify which road segments appear to be high contributors of sediment within the watershed. These road segments were compared with the segments estimated by the models to have high sediment yields. The models identified less than 50% of those roads categorized by field observation as having high erosion potential. WEPP: Road matched more closely to the field observations than SEDMODL and STJ-EROS. To be useful tools for watershed management in the tropics, a unified method for calculating sediment delivery is needed as well as an adjustment to model input parameters so that they better reflect conditions in tropical watersheds. / Master of Science

No description available.

The overall goal of this research was to increase, relative to targeting recommendations, the cost-effectiveness of pollution reduction measures within a watershed. The goal was met through development of an optimization procedure for best management practice (BMP) placement at the watershed level. The procedure combines an optimization component, written in the C++ language, with spatially variable nonpoint source (NPS) prediction and economic analysis components, written in the ArcView geographic information system scripting language. The procedure is modular in design, allowing modifications or enhancements to the components while maintaining the overall theory. The optimization component uses a genetic algorithm to optimize a lexicographic multi-objective function of pollution reduction and cost increase. The procedure first maximizes pollution reduction to meet a specified goal, or maximum allowable load, and then minimizes cost increase. For the NPS component, a sediment delivery technique was developed and combined with the Universal Soil Loss Equation to predict average annual sediment yield at the watershed outlet. Although this evaluation considered only erosion, the NPS pollutant fitness score allows for evaluation of multiple pollutants, based on prioritization of each pollutant. The economic component considers farm-level public and private costs, accounting for crop productivity levels by soil and for enterprise budgets by field. The economic fitness score assigns higher fitness scores to scenarios in which costs decrease or are distributed more evenly across farms. Additionally, the economic score considers the amounts of cropland, hay, and pasture needed to meet feed and manure/poultry litter spreading requirements. Application to two watersheds demonstrated that the procedure optimized BMP placement, locating scenarios more cost-effective than a targeting strategy solution. The optimization procedure identified solutions with lower costs than the targeting strategy solution for the same level of pollution reduction. The benefit to cost ratio, including use of the procedure and implementation of resulting solutions, was demonstrated to be greater for the optimization procedure than for the targeting strategy. The optimization procedure identifies multiple near optimal solutions. Additionally, the procedure creates and evaluates scenarios in a repeated fashion without requiring human interaction. Thus, more scenarios can be evaluated than are feasible to evaluate manually. / Ph. D.

Forests of the Southeastern United States produce approximately 12% of all the world's wood products and represent 40% of all U.S. timberland, thus emphasizing the importance of Southeast in support of the United States' role as the world's largest timber producer. Producing such quantities of timber requires a substantial areas of forest harvest operations, which have the potential to disturb soils, facilitate erosion and potentially reduce water quality. Harvest sites routinely contain operational features such as skid trails, harvest areas, haul roads, decks/landings and stream crossings, all of which have the potential to influence erosion and sediment deposition in streams. Forestry best management practices (BMPs) were created to minimize the effects of harvesting operations on sedimentation and are implemented at varying levels throughout the Southeastern U.S. We quantified the area of these features on 111 recent harvest sites throughout 11 Southeastern states and three physiographic groupings (Mountains, Piedmont, Coastal Plain). No significant differences were found between the groupings with regard to the percent of area occupied by each operational feature. Decks, haul roads, skid trails, and stream crossings comprised an average of 1.43%, 3.21%, 7.03%, and 0.19% of the harvest operations. Roads, decks, skid trails, and structures were combined into an access feature category. These combined access features occupied 13.0% of harvests in the Mountains, 10.2% in the Piedmont, and 10.4% in the Coastal Plain (10.4%). A companion study was developed to trap sediment delivered to the stream and quantify the sediment delivery ratios (SDRs) on a subset of harvests sites in order to determine the average amount of eroded material that could reach a stream from each specific operational feature following a harvest. Across all groupings, stream crossings had the highest average SDR (34.32%), while skid trails had the second highest SDR (21.04%). Substantial site variability resulted in large SDR differences with few meaningful significant differences, but stream crossings, skid trails, and haul roads had sufficiently high sediment delivery ratios across all groupings to warrant additional BMP focus on these areas. / Master of Science / The Southeastern United States is a major producer of forests and forest products, comprising about 40% of US timberland and 12% of global wood products. Support of this industry requires that over 4 million acres of forests are harvested annually across the southeastern U.S. and improper or under usage of forestry best management practices could result in soil erosion and subsequent transport to streams as sediment. Previous research indicates that different operational and access features found on logging sites have different erosion rates yet little data exists which document the percentages of erosion that is delivered as sediment to streams. Skid trails (trails that forestry equipment use within a harvesting operation) compromised the largest access feature average percent area (second to harvest area), followed by haul roads, then decks (area where equipment is kept and logs are processed and loaded), and finally stream crossings with the smallest average area. Stream crossings, skid trails and haul roads consistently had the highest average sediment delivery ratios for all groupings combined. However, substantial site variability resulted in large sediment delivery ratio differences with few meaningful significant differences.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / This work aims to present an analysis through the experiments driven in a watershed to support the future studies that point out to identification and checking the causes that promote the degradation in the semiarid region of the Northeast of Brazil. It was taken two watershed cited in the Escola AgrotÃcnica Federal de Iguatu â EAFIGT located in the Iguatu County, CearÃ, Brazil, It was made the morphometrical characterization, the identification of the vegetation (herbaceous and arboreal) substrates and the evaluation of the sediments transport related to physical aspects with the hydrological processes. The experiment was developed during the first semester of 2008 (rainfall station). The considered morphometrical aspects were: length and sinuosity of the main stream and slope, area, length, form factor, compactness coefficient, concentration time of the watershed, as well as the runoff time. The cover vegetation was estimated account all species present in a sampled space of 10 m x 10 m in a randomized design with three replications in each watershed. From the all computed individuals present in each sampled space, the density of vegetable was obtained by area and the population was estimated in the watersheds. In the evaluation of the sediments transport it was used the following equipments: suspended sediment flow collectors, weir parshall and meteorological station. The station was made in the Universidade Federal do CearÃ- UFC/DENA/LEMA. Results showed that cover vegetation was composed, basically by 23 species, being the most abundant Hyptis sauaviolens (L.) point (Bambural) and Hyptis sp. (Melosa) herbaceous and arboreal shrubby the Aspidosperma pyrifolium Mart (Pereiro). The plant density for unity of area was 1,43 individual/m2 and 1,18 individual/m2 for the watershed B1 and B2, respectively. The estimated of vegetation population was 16,395 individuals for B1 and 24,421 individuals for B2, respectively. During the studied period, the air temperature went from 41 oC to 20 oC and the relative humidity went from 100% to 35%. The most intensity rainfall for 5 minutes was 140 mm h-1 in an event of 126 mm. The watershed areas were 1,15 ha and 2,06 ha for the watershed B1 and B2, respectively, with slope 8,7 for B1 and 10,6 %. for B2. The sinuosity of streams were 1,2 for the B1 and 1,4 for B2. The sediment delivery during the collected period was 9,22 and 17,95 kg for watersheds B1 and B2, respectely. The peak of flow registered in the B2 watershed was 740 m3 h-1 while in the B1 watershed was not possible register the peak flow. In spite of the experimental area present a good cover vegetable, it was identified the human activity. Although the number of vegetable species is high, it points out to succession stage. Even with the same characteristic pair watersheds can have different hydrologic behavior. / Este trabalho teve como objetivo a apresentaÃÃo de uma anÃlise a partir de experimentos conduzidos em micro-bacia para servir de suporte a futuros estudos que visem a identificaÃÃo e monitoramento das causas que levam a degradaÃÃo no Nordeste semi-Ãrido brasileiro. Para isso, foi tomado como unidade duas micro-bacias localizadas no municÃpio de Iguatu-Ce, pertencentes à Escola AgrotÃcnica Federal de Iguatu-EAFIGT e efetuada a caracterizaÃÃo morfomÃtrica, a identificaÃÃo dos substratos herbÃceo e arbÃreo e a avaliaÃÃo do transporte de sedimentos relacionado os aspectos fÃsicos com o processo hidrolÃgico. Considerou-se o perÃodo de experimento o primeiro semestre de 2008 (estaÃÃo chuvosa). Os aspectos morfomÃtricos obtidos foram: comprimento dos cursos e da bacia, declividade da bacia, Ãrea da bacia, fator de forma, coeficiente de compacidade, tempo de concentraÃÃo, sinuosidade do curso principal, tempo mÃdio de escoamento superficial. Para a identificaÃÃo do extrato vegetal foi feito levantamento das espÃcies vegetais em amostragem aleatÃria, com trÃs repetiÃÃes para cada micro-bacia no espaÃamento de 10 x 10 m. Computando todos os indivÃduos de cada espÃcie, a partir desses dados foi obtida a densidade de indivÃduos por Ãrea e estimada a populaÃÃo nas Ãreas das micro-bacias. Na avaliaÃÃo do transporte de sedimentosfoi procedida a instalaÃÃo de equipamentos: coletores de sedimentos em suspensÃo no curso dos cÃrregos, calhas Parshall e estaÃÃo hidro-meteorologica. A estaÃÃo foi confeccionada na Universidade Federal do CearÃ-UFC/DENA/LEMA. Foram identificadas no trabalho 23 espÃcies vegetais, sendo as mais abundantes Hyptis sauaviolens (L.) point (Banbural) e Hyptis sp. (Melosa) as herbÃceas e arbÃrea arbustiva o Aspidosperma pyrifolium Mart (Pereiro). A densidade de indivÃduos por unidade de Ãrea obtida foram 1,43 indivÃduo/m2 e 1,18 indivÃduo/m2 para as micro-bacias B1 e B2, respectivamente. As populaÃÃes estimadas foram 16.395 indivÃduos para B1 e 24.421 indivÃduos para B2. Durante o perÃodo de estudo a temperatura do ar variou de 20 e 41 oC e a umidade relativa variou desde valores de 35% a saturaÃÃo. A chuva de intensidade mÃxima para 5 minutos foi 140 mm h-1 em um evento de 126 mm. As Ãreas das micro-bacias B1 e B2 foram, respectivamente, 1,15 ha e 2,06 ha, com declividades 8,7 e 10,6%. Os cÃrregos apresentaram-se com sinuosidade de 1,2 para a B1 e 1,4 para a B2. A produÃÃo de sedimentos em suspensÃo coletada para o perÃodo observado foi 9,22 e 17,95 kg. A vazÃo mÃxima para B2 foi de 740 m3 h-1, para a micro-bacia B1 nÃo foi possÃvel o registro da vazÃo mÃxima. Apesar da Ãrea experimental apresentar uma boa cobertura vegetal, a aÃÃo antrÃpica existe. O nÃmero de espÃcies vegetais à bem diversificado, mas aponta estagio de sucessÃo. Mesmo com caracterÃsticas semelhantes bacias adjacentes podem ter respostas hidro-sedimentolÃgicas diferentes.

The first part of this thesis aims at defining the conditions triggering muddy floods in the Belgian loess belt. On average, each municipality is confronted with 3.6 muddy floods each year. Annual costs associated with their off-site impacts are estimated at € 16-172 millions for the entire Belgian loess belt. A topographic threshold is derived to predict the source areas of muddy floods. Furthermore, the storms required to produce a flood are, on average, smaller in May and June (25 mm) than between July and September (46 mm). This difference is explained by the variability of soil surface characteristics that determine the runoff potential of cultivated soils (soil cover by crops and residues, soil surface crusting and roughness). Steady state infiltration rates of cropland and grassed areas were characterised in the field using a 0.5 m2-portable rainfall simulator. Overall, grassed areas have a lower infiltration rate (16-23 mm h-1) than croplands (25-52 mm h-1). Muddy floods are mostly observed between May-September because of the coincidence of critical soil surface conditions for runoff generation with the most erosive storms. After an adaptation of its decision rules to the local conditions, the STREAM expert-based model provides satisfactory runoff/erosion predictions at the catchment scale. The second part of the thesis aims at evaluating the effectiveness of measures to control muddy floods. A modelling case-study showed that peak discharge was reduced by more than 40% by installing a grassed waterway and a dam at the outlet of a 300 ha-catchment. Monitoring the same catchment (2002-2007) demonstrated that the grassed waterway as well as three dams prevented any muddy flood in the downstream village despite the occurrence of several extreme storms (with a maximum return period of 150 years). Peak discharge was reduced by 69%. Specific sediment yield dropped from 3.5 t ha-1 yr-1 to a mean of 0.5 t ha-1 yr-1 after the installation of the control measures, thereby reducing drastically sediment transfer to the alluvial plain. Finally, a methodology is provided to implement grassed waterways and earthen dams in other dry valleys in the Belgian loess belt and comparable environments.

ALVES, Nilvia Nara de Lucena. Caracterização de micro-bacia hidrográfica experimental no semi-árido brasileiro como suporte a estudos de degradação. 2008. 74 f. Dissertação (Mestrado em engenharia agrícola)- Universidade Federal do Ceará, Fortaleza-CE, 2008. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-24T19:46:06Z No. of bitstreams: 1 2008_dis_nnlalves.pdf: 4979980 bytes, checksum: 8b61f9155fbd42998a611ce5ad3a5866 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-07-21T20:20:29Z (GMT) No. of bitstreams: 1 2008_dis_nnlalves.pdf: 4979980 bytes, checksum: 8b61f9155fbd42998a611ce5ad3a5866 (MD5) / Made available in DSpace on 2016-07-21T20:20:29Z (GMT). No. of bitstreams: 1 2008_dis_nnlalves.pdf: 4979980 bytes, checksum: 8b61f9155fbd42998a611ce5ad3a5866 (MD5) Previous issue date: 2008 / This work aims to present an analysis through the experiments driven in a watershed to support the future studies that point out to identification and checking the causes that promote the degradation in the semiarid region of the Northeast of Brazil. It was taken two watershed cited in the Escola Agrotécnica Federal de Iguatu – EAFIGT located in the Iguatu County, Ceará, Brazil, It was made the morphometrical characterization, the identification of the vegetation (herbaceous and arboreal) substrates and the evaluation of the sediments transport related to physical aspects with the hydrological processes. The experiment was developed during the first semester of 2008 (rainfall station). The considered morphometrical aspects were: length and sinuosity of the main stream and slope, area, length, form factor, compactness coefficient, concentration time of the watershed, as well as the runoff time. The cover vegetation was estimated account all species present in a sampled space of 10 m x 10 m in a randomized design with three replications in each watershed. From the all computed individuals present in each sampled space, the density of vegetable was obtained by area and the population was estimated in the watersheds. In the evaluation of the sediments transport it was used the following equipments: suspended sediment flow collectors, weir parshall and meteorological station. The station was made in the Universidade Federal do Ceará- UFC/DENA/LEMA. Results showed that cover vegetation was composed, basically by 23 species, being the most abundant Hyptis sauaviolens (L.) point (Bambural) and Hyptis sp. (Melosa) herbaceous and arboreal shrubby the Aspidosperma pyrifolium Mart (Pereiro). The plant density for unity of area was 1,43 individual/m2 and 1,18 individual/m2 for the watershed B1 and B2, respectively. The estimated of vegetation population was 16,395 individuals for B1 and 24,421 individuals for B2, respectively. During the studied period, the air temperature went from 41 oC to 20 oC and the relative humidity went from 100% to 35%. The most intensity rainfall for 5 minutes was 140 mm h-1 in an event of 126 mm. The watershed areas were 1,15 ha and 2,06 ha for the watershed B1 and B2, respectively, with slope 8,7 for B1 and 10,6 %. for B2. The sinuosity of streams were 1,2 for the B1 and 1,4 for B2. The sediment delivery during the collected period was 9,22 and 17,95 kg for watersheds B1 and B2, respectely. The peak of flow registered in the B2 watershed was 740 m3 h-1 while in the B1 watershed was not possible register the peak flow. In spite of the experimental area present a good cover vegetable, it was identified the human activity. Although the number of vegetable species is high, it points out to succession stage. Even with the same characteristic pair watersheds can have different hydrologic behavior. / Este trabalho teve como objetivo a apresentação de uma análise a partir de experimentos conduzidos em micro-bacia para servir de suporte a futuros estudos que visem a identificação e monitoramento das causas que levam a degradação no Nordeste semi-árido brasileiro. Para isso, foi tomado como unidade duas micro-bacias localizadas no município de Iguatu-Ce, pertencentes à Escola Agrotécnica Federal de Iguatu-EAFIGT e efetuada a caracterização morfométrica, a identificação dos substratos herbáceo e arbóreo e a avaliação do transporte de sedimentos relacionado os aspectos físicos com o processo hidrológico. Considerou-se o período de experimento o primeiro semestre de 2008 (estação chuvosa). Os aspectos morfométricos obtidos foram: comprimento dos cursos e da bacia, declividade da bacia, área da bacia, fator de forma, coeficiente de compacidade, tempo de concentração, sinuosidade do curso principal, tempo médio de escoamento superficial. Para a identificação do extrato vegetal foi feito levantamento das espécies vegetais em amostragem aleatória, com três repetições para cada micro-bacia no espaçamento de 10 x 10 m. Computando todos os indivíduos de cada espécie, a partir desses dados foi obtida a densidade de indivíduos por área e estimada a população nas áreas das micro-bacias. Na avaliação do transporte de sedimentosfoi procedida a instalação de equipamentos: coletores de sedimentos em suspensão no curso dos córregos, calhas Parshall e estação hidro-meteorologica. A estação foi confeccionada na Universidade Federal do Ceará-UFC/DENA/LEMA. Foram identificadas no trabalho 23 espécies vegetais, sendo as mais abundantes Hyptis sauaviolens (L.) point (Banbural) e Hyptis sp. (Melosa) as herbáceas e arbórea arbustiva o Aspidosperma pyrifolium Mart (Pereiro). A densidade de indivíduos por unidade de área obtida foram 1,43 indivíduo/m2 e 1,18 indivíduo/m2 para as micro-bacias B1 e B2, respectivamente. As populações estimadas foram 16.395 indivíduos para B1 e 24.421 indivíduos para B2. Durante o período de estudo a temperatura do ar variou de 20 e 41 oC e a umidade relativa variou desde valores de 35% a saturação. A chuva de intensidade máxima para 5 minutos foi 140 mm h-1 em um evento de 126 mm. As áreas das micro-bacias B1 e B2 foram, respectivamente, 1,15 ha e 2,06 ha, com declividades 8,7 e 10,6%. Os córregos apresentaram-se com sinuosidade de 1,2 para a B1 e 1,4 para a B2. A produção de sedimentos em suspensão coletada para o período observado foi 9,22 e 17,95 kg. A vazão máxima para B2 foi de 740 m3 h-1, para a micro-bacia B1 não foi possível o registro da vazão máxima. Apesar da área experimental apresentar uma boa cobertura vegetal, a ação antrópica existe. O número de espécies vegetais é bem diversificado, mas aponta estagio de sucessão. Mesmo com características semelhantes bacias adjacentes podem ter respostas hidro-sedimentológicas diferentes.

No description available.

No description available.