William M. Marsh

Hydrogeomorphic considerations in development planning and stormwater management, central Texas Hill Country, USA

Watershed ordinances in Austin, Texas, USA, are intended to protect streams from stormwater degradation. Their adequacy is being questioned, however, where development is advancing into the Hill Country northwest and southwest of the city. Detailed investigation into hillslope runoff reveals that several important facts were overlooked in the ordinances, including locally high infiltration rates and drainage basins, which function as partial area systems. As a result, development planning is not taking advantage of the natural mitigation potential of the land. Roads cut across infiltration and moisture retention areas on side slopes, enlarging the partial area system feeding streams with stormflows. In addition, most residential planning is not responsive to the stepped microtopography of Hill Country drainage basins and the critical scale at which local runoff processes operate. Recommendations include adjusting the scale and configuration of development to conform with local runoff processes and features and taking advantage of the water-absorbing capacities of basin side slopes. The lesson for ordinance writers is that standard models of community stormwater ordinances are not appropriate for all terrains, especially complex ones like the Texas Hill Country.

Hydro-ecological implications of edge cities

Abstract A spatial and temporal classification of the embryonic forms of edge cities within their physical/environmental context is developed. Three classes of edge cities are identified as having developed along the expressway system: (1) transportation/service; (2) transportation/service/commercial; and (3) corporate/industrial. Each edge-city class has special implications for the hydro-ecological environment. A case study was used to assess the effects on these three classes on several basic indicators of impacts from stormwater runoff, groundwater contamination, and habitat fragmentation. The results indicate that transport/service edge-cities may pose a significant threat of contamination to the groundwater resource owing to the existence of underground storage-tanks and the transport of hazardous substances. In transport/service/commercial edge-cities, runoff volumes increase dramatically and water quality declines, as development displaces wetlands and creates impervious land cover. At a corporate/industrial edge-city location, habitat fragmentation is higher, as reflected by a decreased patch size for forest and wetland areas.

Nourishment of perched sand dunes and the issue of erosion control in the Great Lakes

Although limited in coverage, perched sand dunes situated on high coastal bluffs are considered the most prized of Great Lakes dunes. Grand Sable Dunes on Lake Superior and Sleeping Bear Dunes on Lake Michigan are featured attractions of national lakeshores under National Park Service management. The source of sand for perched dunes is the high bluff along their lakeward edge. As onshore wind crosses the bluff, flow is accelerated upslope, resulting in greatly elevated levels of wind stress over the slope brow. On barren, sandy bluffs, wind erosion is concentrated in the brow zone, and for the Grand Sable Bluff, it averaged 1 m3/yr per linear meter along the highest sections for the period 1973–1983. This mechanism accounts for about 6,500 m3 of sand nourishment to the dunefield annually and clearly has been the predominant mechanism for the long-term development of the dunefield. However, wind erosion and dune nourishment are possible only where the bluff is denuded of plant cover by mass movements and related processes induced by wave erosion. In the Great Lakes, wave erosion and bluff retreat vary with lake levels; the nourishment of perched dunes is favored by high levels. Lake levels have been relatively high for the past 50 years, and shore erosion has become a major environmental issue leading property owners and politicians to support lake-level regulation. Trimming high water levels could reduce geomorphic activity on high bluffs and affect dune nourishment rates. Locally, nourishment also may be influenced by sediment accumulation associated with harbor protection facilities and by planting programs aimed at stabilizing dunes.

Reading Topographic Maps

Interpreting the colored lines, areas, and other symbols is the first step in using topographic maps. Features are shown as points, lines, or areas, depending on their size and extent. For example, individual houses may be shown as small black squares. For larger buildings, the actual shapes are mapped. In densely built-up areas, most individual buildings are omitted and an area tint is shown. On some maps, post offices, churches, city halls and other landmark buildings are shown within the tinted area. The first features usually noticed on a topographic map are the area features such as vegetation (green), water (blue), some information added during update (purple), and densely built-up areas (gray or red). Many features are shown by lines that may be straight, curved, solid, dashed, dotted, or in any combination. The colors of the lines usually indicate similar kinds or classes of information: brown for topographic contours; blue for lakes, streams, irrigation ditches, etc.; red for land grids and important roads; black for other roads and trails, railroads, boundaries, etc.; and purple for features that have been updated using aerial photography, but not field verified.

Physical Geography: The Global Water System

Chapter Overview Few things on Earth are as central to physical geography as water or, to put another way, without water Earths physical geography would be a much simpler matter than it is. So we start this section of the book with an overview of this magnificent system, a glimpse into the big picture of water. The discussion is driven by some compelling questions including how Earth got its water, how much water is held where on the planet, how the water-exchange system, the hydrologic cycle, works, and how on land the system is organized into subsystems. We are led to a model called the water budget that helps us understand how the subsystems like watersheds, glaciers, and soils function. We then give some thought to hydrologic landscapes and what makes humid and arid landscapes different in terms of where water is stored and accessed by plants. Finally, and consistent with one of the books main themes, Earth is a planet of changing systems, and so it is with the hydrologic system, for no matter where we are this great system is constantly changing around us. Introduction Of the many things that make Earth unique as a planet, one of the most striking is its water system. It is not merely the presence of a large water supply that is striking – Mars also has abundant water – but rather the makeup, distribution, and dynamics of Earths water system.

Earth's Radiation and Heat Systems Over Land and Water

Chapter Overview This chapter is about the concept of balance in the Earth energy system. We deal first with the input side of the system by bringing solar radiation into the Earths atmosphere to see what happens when it passes through air and strikes the Earths surface. Since geography is our main concern, we are particularly interested in factors, such as cloud cover and the curvature of the Earth, which influence the global distribution of solar energy. Next is the output side of the system. To keep from overheating, Earth must release back into space the energy it gains from the Sun. But before this can take place, solar radiation must be converted into heat and then converted back into radiation in order to leave the atmosphere. We then examine the balance between Earths energy inflows and outflows. The chapter ends with a look at global temperature patterns and the geographic controls on those patterns, in particular the world distribution of land and water. Introduction Uncle Bill could have been a character out of a Jack London novel. At least thats how I, at the age of eight or nine, saw him. On this occasion he was home on Christmas leave from the Air Force and he thought it might be challenging for us to experience a winter night camping out in the northern Michigan woods. But to make it truly challenging, he suggested that we “rough it” by doing without the standard cold weather gear.

Atmospheric Moisture, Precipitation and Weather Systems

Chapter Overview The atmosphere is a complex system, sometimes described as chaotic in nature. In this chapter we examine one of the principal components of that system, the precipitation system, and find that it is indeed complex, but within that complexity, there is a good deal of order to be found in its processes and patterns. We want to learn how precipitation is produced and how and where it is delivered. We trace our way through the atmospheric moisture system, beginning with a brief examination of water vapor, humidity, and condensation and then go on to the processes and causes of precipitation and their geographic circumstances, including the nature of storm systems such as thunderstorms, tornadoes, and hurricanes. The chapter ends with some insights into the nature of violent storms and some of their consequences. Introduction The town was nothing more than a general store and saloon on a side road a few hundred feet off US-21 in northern Nebraska. A half mile or so to the north you could see a few houses and beyond them endless farm fields and plains stretching into the horizon. Thunderstorms with great billowing heads dominated the hot afternoon sky creating shadowy islands in an otherwise sunny landscape. Inside the store we milled around looking at antiques and chatting with the clerk. Suddenly, a siren sounded. Almost immediately the clerk said, “Its a severe storm warning, probably a thunderstorm, we get them all the time.”

Physical Geography: Mountain Systems, Earthquakes, and Volcanoes

Chapter Overview The Battle of Gettysburg, a pivotal event in American history, was strongly influenced by the lay of the land. But instances of landforms influencing battles and even shaping the development of countries and entire cultures are not unique in the annals of world history. Mountain ranges in particular have influenced where political boundaries are drawn, how religions and languages are distributed, and who trades with whom. So it behooves us to learn about mountains, both their geological and geographical aspects. In this chapter we want to learn first about their anatomies, that is, what do mountains look like on the inside? This will lead to a brief survey of mountain types and how rock is deformed by tectonic forces into folded, faulted, and volcanic structures. The remainder of the chapter is devoted to an examination of the two most studied and feared phenomena of mountain lands, earthquakes and volcanoes, with a glimpse at some of the most notorious of these natural villains including the infamous Mt. Pelee explosion of 1902 that killed 28,000 people, the more infamous Haitian earthquake of 2010 that killed more than 250,000 people, and the East Japan earthquake and tsunami of 2011 that killed over 25,000 people. The chapter ends on the question of the influence of volcanic eruptions on global weather and climate.

Physical Geography: The Formation and Geographic Organization of the Continents and Ocean Basins

Chapter Overview Plate tectonics is the window to understanding the geographic arrangement of so many of the things we once took for granted when looking at maps of the world. Why the sizes and shapes of the continents and ocean basins and what about those large islands, chains of islands, and the great belts of mountains hugging the edges of the continents? We begin with a brief review on the development of the theory itself and then go on to describe the gross features of the Earths crust to provide a geographic framework for the ensuing discussion. This discussion looks into the nature of plate motion, the conditions and features on the plate borders, and the processes that produce earthquakes and volcanoes. We end the chapter briefly examining a few of the many geographic implications of plate tectonics, in particular the distribution of marsupial and placental mammals and the climate and drainage of monsoon Asia. Introduction This is the story of plate tectonics, a theory that ranks with evolution as one of the monumental advances of natural science in the past two centuries. For many reasons, some we have already touched on and many that lie in the pages ahead, this concept is foundational to physical geography. Although the theory of plate tectonics has been with us for only several decades, the roots of this revolutionary idea actually go back several centuries or more.

Physical Geography: Runoff, Streamflow, and Watershed Systems

Chapter Overview Our story begins with a brief look at the runoff systems that feed streams. We are particularly interested in the role the landscape plays in these systems and, in turn, in streamflow; for example, how trees intercept rainfall and how soil soaks up rain that hits the ground. We are also interested in how the atmosphere delivers rainfall and how rainfalls of different intensities and durations influence streamflow. All this is set into the geographic framework of a watershed where networks of streams of various sizes and patterns form elegant water-moving systems. And no story about streams would be complete without addressing flooding, a phenomenon that has baffled and plagued humans for thousands of years. The chapter concludes on a distinctly geographic note, an overview of the 20 largest watersheds of the world, which include the Amazon, Mississippi, Nile, and Yangtze. Introduction Ancient Hindu and Buddhist mythology describe a sacred mountain at the center of the Universe as the source of the Earths great rivers. Early Christian mythology identifies the Garden of Eden as the place where Earths waters divide to form the great rivers. Thousands of years later, in the nineteenth century, we were still speculating on the sources of many great rivers. Scores of explorer/geographers driven by the romance of adventure, scientific curiosity, and political directives ventured into the heart of North America, South America, Asia, and Africa to find the few remaining undiscovered river sources.